Automatic measurement of dimensional data with a laser tracker

Automatic measurement of dimensional data by laser tracker

[0001] The application of the present invention is that the international filing date is March 14, 2012, the international application number is "PCT/US2012/028984", the national application number is "201280013306. "Automatic measurement of data" is a divisional application of the invention patent application.

[0002] Cross reference of related applications

[0003] This application claims priority to U.S. Provisional Patent Application No. 61/452,314 filed on March 14, 2011, the entire contents of which are incorporated herein by reference. This application also claims the priority of U.S. Patent Application No. 13/340,730 filed on December 30, 2011. The U.S. Patent Application No. 13/340,730 requires U.S. Patent Application No. filed on April 20, 2011 The priority of 13/090, 889, the United States Patent Application No. 13/090, 889 claims the priority of the United States Provisional Patent Application No. 61/326, 294 filed on April 21, 2010, the entire content of these applications Incorporated here by reference. In addition, this application claims the priority of U.S. Provisional Patent Application No. 61/475,703 filed on April 15, 2011, the entire contents of which are incorporated herein by reference. In addition, this application claims the priority of U.S. Provisional Patent Application No. 61/592,049 filed on January 30, 2012, the entire contents of which are incorporated herein by reference. In addition, this application claims the priority of U.S. Patent Application No. 13/407, 983 filed on February 29, 2012. The U.S. Patent Application No. 13/407, 983 requires the U.S. Provisional Patent Application filed on March 3, 2011 No. 61/44 & 823 priority, the entire contents of these two applications are incorporated herein by reference.

Technical field

[0004] The present disclosure relates to, for example, a metrology device such as a laser tracker, and more particularly to the use of one or more locator cameras associated with the laser tracker (for example, as a component of the laser tracker) to automatically identify objects placed on an object A laser tracker for each of the multiple retroreflector targets.

Background technique

[0005] There is an instrument called a laser tracker, which measures the coordinates of a point by emitting a laser beam to a retroreflector target in contact with the point. The instrument determines the coordinates of the point by measuring the distance and two angles to the target. The distance is measured by a distance measuring device such as an absolute distance meter or an interferometer. The angle is measured by an angle measuring device such as an angle encoder. The universal beam control mechanism in the instrument guides the laser beam to the point of interest.

[0006] A laser tracker is a special type of coordinate measuring device that tracks a retroreflector target through one or more laser beams it emits. Another instrument called a total station or tachymeter can measure retroreflectors or points on the diffuse scattering surface. Laser trackers that usually have an accuracy of one thousandth of an inch and in some cases are on the order of one or two microns are generally much more accurate than a total station. This application all adopts the broad definition of laser tracker including total station.

[0007] Generally speaking, a laser tracker emits a laser beam to a retroreflector target usually located on the surface of the object to be measured. A common type of retroreflector target is a spherically mounted retroreflector (SMR), which includes a cube corner retroreflector embedded in a metal ball. The cube corner retroreflector consists of three mutually perpendicular mirrors. The vertex is the common intersection of the three mirrors, located near the center of the sphere. Because of the arrangement of the cube corners in the sphere, the vertical distance from the vertex to any surface of the object where the SMR is located remains almost constant, even when the SMR is rotating. Therefore, when the SMR moves on the surface, the laser tracker can measure the 3D coordinates of the surface by following the position of the SMR. In other words, the laser tracker only needs to measure three degrees of freedom (a radial distance and

Two angles) can express the characteristics of the 3D coordinates of the surface.

[0008] Some laser trackers have the ability to measure six degrees of freedom (DOF), which can include three translations, such as x, y, and z, and three rotations, such as pitch, roll, and yaw. An exemplary six-DOF laser tracker system is described in U.S. Patent No. 7,800,758 ('758) to Bridges et al., which is incorporated herein by reference. The '758 patent discloses a probe that maintains a cube-corner retroreflector with a logo placed on the retroreflector. Retroreflectors with this logo are called six-DOF retroreflectors. The cube corner retroreflector is illuminated by the laser beam from the laser tracker, and the mark on the cube corner retroreflector is captured by the camera in the laser tracker. Calculate three azimuth degrees of freedom based on the image obtained by the camera, such as pitch angle, roll angle and yaw angle. The laser tracker measures the distance and two angles to the apex of the cube corner retroreflector. When the distance of the three translational degrees of freedom and the two angles of the vertices are combined with the three azimuth degrees of freedom obtained through the camera image, the tip of the probe can be found relative to the vertex of the cube corner retroreflector arranged at the predetermined position s position. Such a probe tip can be used, for example, to measure the coordinates of "hidden" features outside the line of sight of the laser beam from a laser tracker.

[0009] A common application of laser trackers is to measure larger objects to see how their actual size compares to the design size (for example, as given by CAD data). Several of these objects may be used in a specific application, and it is generally desirable that these objects be geometrically identical. Any deformation in the geometry of an object initially or over time will affect other operations in the entire system of which the object is a part. For example, if the object is bent or twisted in any way, it will cause manufacturing defects and poor product quality.

[0010] It is known that for measurement purposes, at least three points are usually required to establish the relationship between the laser tracker and the object. As is known in the prior art, the ability of the operator to manually measure these initial points with sufficient accuracy is an area for reference.

[0011] Therefore, an operator who needs a laser tracker or similar measuring device can not have to manually measure a target point (for example, SMR). Instead, the operator of the laser tracker is expected to use the camera system in the laser tracker to automatically measure all target points required for any specific application, thereby significantly reducing the possibility of operator error during the measurement process, and does not require specialized skills and/ Or training.

[0012] More generally, there is a need for a method and system in which the laser tracker automatically performs many functions that must be performed manually before. It is expected that even inexperienced operators will perform measurements and obtain consistent measurements quickly through the laser tracker. Common measurements include tool inspection measurements; for example, a car box in a body-in-white assembly line is an example of a tool to be inspected or monitored. Other examples of tools include sheet metal stamping fixtures, and assembly tools for assembling parts of aircraft structures. Generally speaking, there are tools for almost every part manufactured in automotive or aerospace applications. Therefore, the laser tracker is expected to improve the processing of measuring these tools. In addition, it is desirable to apply the measurement process to the finished part.

Summary of the invention

[0013] A method for measuring through a system includes the steps of: providing a system including a collection of retroreflector targets and a laser tracker. The collection of retroreflector targets includes at least three non-collinear retroreflector targets, at least The three non-collinear retroreflector targets include the first target, the second target and the third target. The laser tracker in the first reference frame is fixed with respect to the tracker environment. The laser tracker has a structure, a first light source, and absolute distance measurement. The instrument, the first angle converter, the second angle converter, the tracking system, the first camera, the second light source and the processor, the structure can be rotated about the first axis and the second axis, and the first light source generates and cooperates with the absolute distance meter The first angle transducer measures the first angle of rotation about the first axis, the second angle transducer measures the second angle of rotation about the second axis, and the tracking system is configured to move the first beam to retroreflect The center of any retroreflector target in the target set, the first camera includes a first lens system and a first photosensitive array

Column, the second light source provides the second beam, and the processor is configured to operate the laser tracker; stores a list of nominal coordinates for the first target, the second target, the third target, and at least one additional point, the nominal coordinate is the first Two three-dimensional coordinates in the reference frame; capture a part of the light emitted by the second light beam and reflected away from the first target, the second target and the third target on the first photosensitive array; leave the first target, the second target and the third target according to the reflection A part of the light of each of the three targets obtains the position of the light spot on the photosensitive array; the positions of the first light spot, the second light spot, and the third light spot on the first photosensitive array are determined with respect to the first target, Correspondence between the nominal coordinates of the second target and the third target; guide the first beam to the first target based at least in part on the position of the first light spot and the nominal coordinates of the first target; An angle transducer and a second angle transducer measure the three-dimensional coordinates of the first target; guide the first beam to the second target based at least in part on the position of the second light spot and the nominal coordinates of the second target; use an absolute distance meter 1. The first angle transducer and the second angle transducer measure the three-dimensional coordinates of the second target; guide the first light beam to the third target based at least in part on the position of the third light spot and the nominal coordinates of the third target; use the absolute distance The meter, the first angle transducer, and the second angle transducer measure the three-dimensional coordinates of the third target; based at least in part on the measured first target, The three-dimensional coordinates of the second target and the third target and the nominal coordinates of the at least one additional point are determined, the three-dimensional coordinates of the at least one additional point in the first reference frame are determined; and the determined three-dimensional coordinates of the at least one additional point are stored.

Description of the drawings

[0014] With reference to the drawings below, the exemplary embodiments shown should not be construed as limiting the full scope of the present disclosure, and wherein elements are similarly numbered in several drawings:

[0015] FIG. 1 is a perspective view of a laser tracker, an auxiliary unit, and an external computer according to an embodiment;

[0016] FIG. 2 is a perspective view of the laser tracker of FIG. 1 according to an embodiment, the laser tracker having an additional narrow field of view camera and an associated light source;

[0017] FIG. 3 shows a two-dimensional representation of a three-dimensional vector diagram;

[0018] FIG. 4A is a front view of a wide-field locator camera set on the rigid structure part of the laser tracker of FIG. 1, wherein the rigid structure is rotated so that the locator camera can simultaneously view multiple retroreflector targets;

[0019] FIG. 4B is a cross-sectional view of the locator camera of FIG. 4A as viewed along the line 410-410 of FIG. 4A;

[0020] FIG. 5A is a perspective view of the laser tracker of FIG. 1 in the first orientation of the object to be measured by the laser tracker under the automatic measurement of various target points on the object by the laser tracker;

[0021] FIG. 5B is a perspective view of the laser tracker of FIG. 1 in the second orientation of the object to be measured by the laser tracker when the laser tracker automatically measures various target points on the object;

[0022] FIG. 6 shows an electronic processor element in a laser tracker according to an embodiment;

[0023] FIG. 7 is a flowchart showing steps of measurement by a system according to an embodiment;

[0024] FIG. 8 is a flowchart showing steps of measurement by a system according to an embodiment;

[0025] FIG. 9 is a flowchart showing steps of measurement by a system according to an embodiment;

[0026] FIG. 10 is a flowchart showing the steps of measuring by the system according to the embodiment; [0027] FIG. 11 is a flowchart showing the steps of measuring by the system according to the embodiment; [0028] FIG. 12 is showing [0029] FIG. 13 is a flowchart showing the steps of measuring through the system according to the embodiment; [0030] FIG. 14 is a flowchart showing the steps of measuring through the system according to the embodiment; A flowchart of the steps; and [0031] FIG. 15 is a flowchart showing the steps measured by the system according to the embodiment.

Detailed ways

[0032] FIG. 1 shows an exemplary laser tracker 10. The exemplary universal beam control mechanism 12 of the laser tracker 10 includes a zenith frame 14 which is mounted on the azimuth base 16 and rotates around the azimuth axis 20. The load 15 is mounted on the zenith frame 14 and rotates around the zenith axis 18. Inside the tracker 10, the zenith mechanical rotation axis (not shown) and the azimuth mechanical rotation axis (not shown) are orthogonal to the universal point 22, which is usually the origin for distance measurement. The laser beam 46 virtually passes through the gimbal point 22 and is directed perpendicularly to the zenith axis 18. In other words, the laser beam 46 is in a plane perpendicular to the zenith axis 18. The laser beam 46 is directed in a desired direction by a motor (not shown) in the tracker, and the motor rotates the load 15 around the zenith axis 18 and the azimuth axis 20. Inside the tracker 10, zenith and azimuth angle encoders (not shown) are attached to the zenith mechanical shaft (not shown) and the azimuth mechanical shaft (not shown), and indicate the angle of rotation with high accuracy . The laser beam 46 is transmitted to an external retroreflector 26, such as the above-mentioned spherical-mounted retroreflector (SMR). By measuring the radial distance between the gimbal point 22 and the retroreflector 26 and the rotation angle about the zenith axis 18 and the azimuth axis 20, the position of the retroreflector 26 is found in the spherical coordinate system of the tracker.

[0033] The laser tracker 10 is a device having a device reference frame 30. The device reference frame may have the universal point 22 as its origin. The reference frame may be fixed with respect to the azimuth base 16, which is generally stationary with respect to the environment. The device reference frame can be represented by various coordinate systems. One type of coordinate system is a Cartesian coordinate system with three vertical axes x, y, and ζ. Another coordinate system is the spherical coordinate system. The point 74 in the spherical coordinate 30 can be represented by a radial distance 73 (r), a first (zenith) angle 72 (0), and a second (azimuth) angle 71 (.) in the spherical coordinate system. The angle θ is obtained by projecting the point 74 on the z axis. The angle 0 is obtained by projecting the point 74 on the xy plane. The laser tracker 10 inherently measures in a spherical coordinate system, but the points measured in spherical coordinates can be easily converted to Cartesian coordinates.

[0034] The target 26 may be in contact with an object under test 61. The object 61 to be measured has an object reference frame 40. The object reference frame can be represented by Cartesian coordinates x, y, and ζ, for example. The X, y, and ζ axes of the object reference frame 40 move with the object 61 and are not necessarily parallel to the corresponding device axes X, y, and ζ of the device reference frame 30. The target 26 may be placed in contact with the surface 61 of the object at a point 63. In order to find the three-dimensional (3D) coordinates of the point 63, the tracker first determines the center of the target 26 using its measured distance and two angles. This can also be used to account for the vector offset of the retroreflector reference point (for example, cube corner vertex) with respect to the center of the spherical contact surface of the target 26. In order to move from the target center to the surface of the workpiece, the position of the center point is shifted by an amount equal to the radius of the spherical target surface. In the embodiment, by measuring several points close to the contact point 63, the offset direction is found to determine the surface normal at the point 63.

[0035] The laser beam 46 may include one or more laser wavelengths. For the sake of clarity and conciseness, a steering mechanism of the type shown in Figure 1 is adopted in the following discussion. However, other types of steering mechanisms are also possible. For example, the laser beam can be reflected from a mirror rotating around the azimuth axis and the zenith axis. As another example, two turning mirrors driven by an actuator such as a galvanometer motor can be used to steer the light beam. In the latter case, the beam can be steered without providing the azimuth and zenith mechanical axis. The technology described here is feasible regardless of the type of steering mechanism.

[0036] In the exemplary laser tracker 10, the camera 52 and the light source 54 are arranged on the load 15. The light source 54 illuminates one or more retroreflector targets 26. In the embodiment, the light source 54 is an LED that is electrically driven to repeatedly emit pulsed light. Each camera 52 includes a photosensitive array and a lens placed in front of the photosensitive array. The photosensitive array can be, for example, a CMOS or CCD array. In an embodiment, the lens has a wider field of view, such as 30 or 40 degrees. The purpose of the lens is to form an image of the object in the field of view of the lens on the photosensitive array. Generally, at least one light source 54 is placed near the camera 52, so the light from the light source 54 reflects off each retroreflector target 26 onto the camera 52. (In order to illuminate the retroreflector target in a way that can be seen on the camera 52, the light source 54 must be close to the camera; otherwise the reflected light will be reflected at an excessive angle and

Missed the camera. ) In this way, it is easy to distinguish the retroreflector image from the background on the photosensitive array, because their image spots are brighter than the background object and are pulsed. In the embodiment, two cameras 52 and two light sources 54 are placed around the laser beam 46. By using two cameras in this way, the principle of triangulation can be used to find the three-dimensional coordinates of any SMR in the camera's field of view. In addition, when the SMR moves from point to point, the three-dimensional coordinates of the SMR can be monitored. The use of two cameras for this purpose is described in US Published Patent Application No. 2010/0128259 by Bridges et al., the contents of which are incorporated herein by reference.

[0037] The auxiliary unit 50 may be a component of the laser tracker 10. The purpose of the auxiliary unit 50 is to provide electrical power to the laser tracker body, and in some cases, to provide calculation and timing capabilities to the system. By transferring the function of the auxiliary unit 50 to the tracker body, the auxiliary unit 50 can be completely eliminated. In most cases, the auxiliary unit 50 is attached to the general-purpose computer 60. The application software loaded into the general-purpose computer 60 can provide application capabilities such as reverse engineering. By directly establishing the computing power of the general-purpose computer 60 in the laser tracker 10, the general-purpose computer 60 can also be completely eliminated. In this case, a user interface that may provide keyboard and mouse functions can be built in the laser tracker 10. The connection between the auxiliary unit 50 and the computer 60 may be wireless or through a wire cable. The computer 60 may be connected to the network, and the auxiliary unit 50 may also be connected to the network. Through the computer 60 or the auxiliary unit 50, multiple instruments (for example, multiple measuring instruments or actuators) can be connected together. In the embodiment, the auxiliary unit is omitted, and the laser tracker 10 and the computer 60 are directly connected.

[0038] In an alternative embodiment of the present invention, the laser tracker 10 may simultaneously utilize both the wide field of view (FOV) and the narrow FOV camera 52 on the laser tracker 10. Various exemplary methods of using such cameras at the same time are described below.

[0039] In the first embodiment, one of the cameras 52 in FIG. 1 is a narrow FOV camera, and the other camera 52 is a wide FOV camera. With this configuration, the wide FOV camera 52 recognizes the retroreflector target 26 in a wide angle range. The laser tracker 10 rotates the beam 46 in the direction of the specially selected retroreflector target 26 until the retroreflector target 26 is in the FOV of the narrow FOV camera 52. Then the laser tracker 10 can execute the following method, using the images on the two cameras 52 installed on the laser tracker 10 to find the position of the retroreflector target. This is done to find the best estimate of the position of the retroreflector target 26.

[0040] In another embodiment shown in FIG. 2, both cameras 52 are wide FOV cameras. In addition, there is a narrow FOV camera 58 and an adjacent light source 56. Two wide FOV cameras 52 determine the three-dimensional position of the retroreflector target 26 and steer the tracker beam 46 to the target 26. When the narrow FOV camera 58 also sees the retroreflector target 26, the information provided by all three cameras 52, 58 is used to calculate the three-dimensional position of the retroreflector target 26.

[0041] In another embodiment, the two wide FOV cameras 52 in FIG. 1 are used to determine the position of the target and steer the laser beam to it. Similar to the azimuth camera 210 shown in FIGS. 2 and 7 of the aforementioned US Patent No. 7,800,758 ('758) (incorporated by reference) to Bridges et al., the azimuth camera views the illuminated retroreflector Small area around target 26. By observing the position of the retroreflector 26 in the photosensitive array of the azimuth camera 210, the laser tracker 10 can immediately direct the laser beam 46 to the center of the retroreflector 26.

[0042] The following describes a method for finding a retroreflector target using the images of the two cameras 52 installed in front of the laser tracker 10 in FIGS. 1 and 2.

[0043] Five reference frames associated with the laser tracker 10: a load reference frame that rotates around the load 15; an azimuth reference frame that rotates around the zenith frame 14; a tracker world reference frame that is fixed with respect to the azimuth base 16; and two A camera frame of reference. The azimuth base 16 is stationary with respect to its environment. The camera 52 includes a lens system (not shown) and a photosensitive array (not shown). A typical description of a camera including a lens system and a photosensitive array is given in FIGS. 4A to 4B.

[0044] In the embodiment, the origin of the load reference frame is at the universal point 22, which is located at a point along the azimuth axis; the y-axis parallel to the zenith direction; and the y-axis is perpendicular to and approximately parallel to the X-axis of the laser beam; And the z-axis perpendicular to the x-axis and y-axis. The camera 52 is fixed with respect to the load reference frame.

[0045] In the embodiment, the origin of the azimuth reference frame is at the universal point 22; the z-axis along the azimuth direction; the y-axis parallel to the zenith axis and perpendicular to the z-axis; and the y-axis perpendicular to the y-axis and the z-axis X axis.

[0046] In the embodiment, the origin of the tracker world reference frame is at the gimbal point 22; the z axis along the azimuth axis; when the angle of the azimuth axis is set to zero degrees, it is perpendicular to the z axis and parallel to the zenith axis. The y axis; and the X axis perpendicular to the y axis and the z axis.

[0047] In an embodiment, the X axis of the camera reference frame is the optical axis of the lens system in the camera. The y axis and the z axis are perpendicular to the X axis and mutually perpendicular, and are respectively aligned with the rows and columns of the pixels of the photosensitive array in the camera 52.

[0048] In the laser tracker 10, the zenith angle and the azimuth angle are the angles of rotation about the zenith axis and the azimuth axis, respectively, and are measured by the zenith encoder and the azimuth encoder, respectively. After knowing the equation of the camera's optical axis in the load reference frame, the zenith angle and the azimuth angle, any one of the 5 reference frames (load reference frame, azimuth reference frame, tracker world reference frame, and two camera reference frames) can be set Transform to any other frame of reference. Usually a transformation matrix is used to achieve this. The transformation matrix is a 4X4 matrix, including a 3X3 rotation matrix and a zoom component for translation. The use of transformation matrices is well known to those skilled in the art.

[0049] The camera 52 and the light source 54 are used to find the position of one or more retroreflector targets 26 in the load reference frame or any other reference frame. If necessary, these targets can be automatically acquired by the laser tracker 10.

[0050] The method of finding the target of the retroreflector in the load reference frame is described below. The first step in the method is to turn on the light source 54 to illuminate the retroreflector 26 and to form an image on the camera 52. In some cases, you can temporarily turn off the lighting and get the difference between the illuminated scene and the non-illuminated scene. In this way, background features can be removed, making it possible to reveal the retroreflector target more clearly. The second step is to use a processor (such as the processor 50) to calculate a center point for each retroreflector light spot on the camera 52 photosensitive array. For example, the center point can be calculated as the centroid. The third step is to establish the direction in the camera reference frame for each center point. In the simplest approximation, the direction is found by drawing a line between the center point and the perspective center of the camera 52. More complex analysis can consider the aberrations of the lens system when determining the direction. The fourth step is to convert the coordinates of the perspective center and the direction used for each center point into a load reference frame. The fifth step is to find the best estimate of the position of the retroreflector target 26 in the load reference frame by solving the simultaneous equations, as described below.

[0051] For each retroreflector target 26, a center point is formed on the light-sensitive array of each of the two cameras 52, and starting from these center points, it is possible to construct an indication from each camera to the retroreflector target 26 Direction of the line. In an ideal situation, two lines intersect at one point, but usually, the two lines are slanted lines that do not intersect exactly. By determining the line segment of the closest path, the best estimate of the intersection position of the two skewed lines is found. The line segment of the nearest path is perpendicular to each of the two slanted lines, and shorter than any other line segment that is perpendicular to the two slanted lines. Generally, the best estimate of the position of the retroreflector target 26 is the midpoint of the line segment of the closest path.

[0052] FIG. 3 shows a two-dimensional representation of a three-dimensional vector diagram. This representation can be obtained, for example, in a top view of the tracker and retroreflector targets from top to bottom. Point 0 is the origin of the load reference frame. The vectors P and R extend from the origin of the laser tracker to the first camera and the second camera, respectively. The vector U represents a line passing through the perspective center of the first camera and having a direction calculated according to the third step of the above method. The vector V represents a line passing through the perspective center of the second camera and having the direction calculated according to the third step of the above method. The vector C represents a line segment extending from the first point on the vector U to the second point on the vector V. The vector C is perpendicular to the vectors U and V.

[0053] One way to find the end point of the vector C is to use the equation:

[0054] P+u U+c C = R+v V, (1)

[0055] Including the scalar quantities u, c, and v, and the vector quantities P, U, C, R, and V.

[0056] In addition, the vector C obeys the constraints:

[0057] C = UXV, (2)

[0058] where X is the cross product operator. The vector equation (1) can be written as the first equation by X, the second equation by y, and the third equation by z. Using the well-known cross product formula, the vector C can be written based on the x, y, and z components of U and V. The x, y, and z components of C are substituted into the first equation, the second equation, and the third equation. The result is three equations for x, y, and z, in which all vectors are known, and only three scalars u, v, and c are left to be determined. Because there are three equations and three unknowns, three values can be determined.

[0059] The three-dimensional end point coordinates Qi and Q of the line segment connecting the vectors U and V along the route of the closest path₂Given by:

[0060] Q] = P+u U, (3)

[0061] Q₂ = R+v Vo (4)

[0062] The best estimate Q of the intersection of the two lines is given by:

[0063] Q=(Qi+Q2)/2. (5)

[0064] If necessary, other mathematical methods can be used to find the best estimate Q of the intersection. For example, an optimization program can be used to find Qi and Q₂Value.

[0065] The above method is described with respect to the laser tracker 10, which has a light beam 46 emitted from the payload 15, and the payload 15 rotates about the zenith axis 18. However, other types of mechanical steering mechanisms are also possible. For example, a steering mirror can be used instead of load 15. In this way, the light beam is directed upward from the azimuth base 16. The beam reaches the steering mirror and reflects out of the tracker housing. A motor attached to the zenith mechanical shaft rotates the steering mirror to aim the beam in the desired direction. In this embodiment, the mirror reference frame is used instead of the load reference frame, but the analysis is the same.

[0066] One or more cameras that are not attached to the laser tracker payload can also be used. These cameras can be attached to the azimuth frame 14, or they can all be installed independently of the laser tracker. The method of finding the relationship between the camera and the reference frame of the laser tracker can be found in a similar way to the above: a certain number of points can be measured by the camera and by the laser tracker, and the measurement results can be used to establish an appropriate transformation matrix.

2 again, because the narrow FOV camera 58 has a smaller angular range covered by each pixel in most cases, it is preferable to give more weight to the reading of the narrow FOV camera 58. The simple way to do this is to modify equation (5) above. For example, if the FOV of a narrow FOV camera 58 is a quarter of the FOV of a wide FOV camera 58, then a reasonable equation used instead of the above equation (5) can be:

[0068] Q = 0.2Q1+0.8Q₂ (6)

[0069] Another mathematical method that can be used is the least squares optimization procedure to find the best estimate for the retroreflector target 26, but with more emphasis on the narrow FOV camera 58 than the reading of the wide FOV camera 52 reading.

4A and 4B, the locator camera 400 allows the laser tracker 10 to quickly determine the approximate positions of multiple retroreflectors in the wider field of view of the laser tracker 10. A plurality of the same light sources 401 are arranged on the ring surrounding the lens 402. Alternatively, fewer light sources or even a single light source can be used. Each light source emits overlapping cones of essentially incoherent light 440, which together form a light cone. Each retroreflector reflects a part of the light from the light cone back to the locator camera 400 as a light beam. FIG. 4B shows one of the light beams 457. The lens 402 focuses the light beam 457 into a spot on the surface of the photosensitive array 404. sense

The optical array 404 is separated from the front principal plane of the lens 402 by the focal length fo of the lens

[0071] The wire 441 provides power from the power source (for example, the auxiliary unit 50) in the laser tracker 10 to the transmitter 401 and the photosensitive array 404. In addition, the wire 441 transmits the pixel data from the photosensitive array 404 to the general-purpose computer 60, for example, for analysis. The computer 60 analyzes the light pattern on the photosensitive array 404 to determine the position of the center point 452 on the photosensitive array 404. In addition, the computer 60 performs this analysis of the pattern formed by the other light beams returning through the retroreflector. In other words, the reflected light beam is focused into a pattern on the photosensitive array 404 through the lens 402. The computer 60 analyzes these patterns to determine the center point of each pattern. According to the position of the center point, the approximate angular direction to each retroreflector can be determined.

[0072] Assume that the retroreflector of interest is a specific retroreflector among a plurality of retroreflectors. If the purpose is to obtain the target and measure the target position through the laser tracker, the following procedure can be carried out. Start the motor and turn the load until the laser beam is aimed at the approximate direction of the specific retroreflector. If the estimation of the target position is good enough, the beam directly locks onto the target and starts tracking of the target. If the estimation of the target position is not good enough, one possibility is to initiate a search, in which the direction of the laser beam is changed in a systematic way. For example, the laser beam can be steered along a spiral pattern. When the laser beam intersects the target, the position detector in the laser tracker senses the reflected light. The signal from the position detector provides enough information so that the motor can directly aim the load at the center of the specific retroreflector. Another possibility is that the operator directly grabs the mechanical mechanism of the laser tracker, such as the payload, and manually directs the beam towards the retroreflector of interest. In one embodiment, if the operator directs the beam sufficiently close to the center of the retroreflector, the LED starts to flash in front of the tracker. If the beam gets closer, the beam starts to lock onto the retroreflector target. If the beam is not sufficiently close to the center of the retroreflector to lock the target, a quick search procedure can be performed to locate the target of the retroreflector.

[0073] In the case that there are two or more locator cameras 52 on the laser tracker 10, the above-mentioned stereo camera calculation can usually be used to directly establish the targets appearing on the retroreflector target 26 and the photosensitive array of the camera 52 One-to-one correspondence between centers. Similarly, if the single camera 52 is placed in the laser tracker in such a way that the light reflected by the target 26 is transmitted to the camera on the optical axis of the laser tracker, the parallax between the camera and the camera is eliminated, and the return can usually be established. Correspondence between the transmitter target and the center of the target appearing on the cameras photosensitive array. If a single camera is used, alternative methods can be used to establish a one-to-one correspondence between the target center and the retroreflector target. One method involves rotating the azimuth axis to different angles and observing the change in position on the photosensitive array of a single camera 52. When the azimuth angle changes, the position of the center on the photosensitive array will change by an amount that depends on the distance from the laser tracker 10 to the retroreflector 26. For a given change in azimuth, as the distance from the retroreflector increases, the change between the two centers on the photosensitive array decreases. A similar procedure can be performed by changing the zenith angle of the laser tracker instead of the azimuth angle. A more detailed description of this procedure is described with reference to Figure 18 of U.S. Patent Application No. 2011/0260033 ('033), which is incorporated herein by reference.

[0074] In some cases, one or more cameras on the laser tracker are accurate enough to direct the beam from the laser tracker to the center of the target sufficiently close to the retroreflector so that the beam reflected back to the laser tracker Picked up by the position detector, causing the laser beam to start tracking the target. In this case, the software that controls the laser tracker can automatically guide the beam from the tracker to each target, so that the higher accuracy of the laser tracker distance meter and angle encoder is transformed into three-dimensional coordinate values. In other cases, one or more cameras on the laser tracker may not be accurate enough to immediately direct the beam from the laser tracker to the center of the target sufficiently close to the retroreflector so that the position detector can immediately detect the beam and start tracking . In this case, the beam from the laser tracker can be aimed at the target, and the beam is guided in the search pattern to locate the target, as described above. By repeating this procedure for each target in the measurement volume, more accurate three-dimensional coordinates can be obtained for each target point. The more accurate three-dimensional coordinates of the target point is important because it

They enable the software that controls the laser tracker to effectively perform automatic measurement of target points without the need for intermediate target search.

[0075] As suggested by the above discussion, certain aspects of the present invention require obtaining a one-to-one relationship between the target point viewed by one or more cameras on the laser tracker and the list of three-dimensional coordinates of the target point of the retroreflector. Correspondence. Some methods of obtaining a list of the three-dimensional coordinates of the target point are described below. In some cases, the list has nominal three-dimensional coordinates, which differ from the actual three-dimensional coordinates by a large amount. In other cases, the list may have more accurate three-dimensional coordinates.

[0076] In one embodiment, a list of three-dimensional coordinates between the laser tracker and the target point on the object to be measured is obtained according to the CAD model describing the target position on the object.

[0077] In another embodiment, the one-to-one correspondence between the target point and the list of three-dimensional coordinates is obtained by performing three-dimensional measurement on each point observed by the camera. This three-dimensional measurement can be performed before the current measurement phase.

[0078] In some cases, the images of the target point on one or more cameras may be separated too closely, and the one-to-one correspondence between the target point and the light point on the camera image cannot be determined immediately. In this case, the above method can be used to measure points with a laser tracker. For example, a laser tracker can direct the beam to the target. The laser tracker can then directly measure the target position, or, if necessary, with the help of a search program to measure the target position.

[0079] An important aspect of the present invention is the establishment of the relationship between the reference frame of the laser tracker and the reference frame of the object to be measured. Another way to express the same idea is to say that it is important to have a method of converting the reference frame of the laser tracker to the reference frame of the object to be measured or vice versa.

[0080] Three methods for establishing this relationship are taught here. In the first method, at least three retroreflector target points are measured by a laser tracker. In the second method, at least two target points are measured by a laser tracker, and at least two inclination angles are measured by an inclinometer set on each of the laser tracker and the target to be measured. In the third method, a single six-degree-of-freedom (DOF) camera is measured by a laser tracker with six DOF measurement capabilities. By combining the information obtained according to any of the three methods, the laser tracker can be placed in the reference frame of the object to be measured. Similarly, the object to be measured can be placed in the reference frame of the laser tracker.

[0081] A brief description of the method of placing the object to be measured in the reference frame of the tracker based on the information obtained by the above measurement is given below. For the laser tracker measuring three retroreflector target points, by allowing one of the three measuring points to be the origin of the local reference frame of the object to be measured, allowing the second measuring point to establish the X axis, and allowing the third The measurement point establishes the component in the y direction, and the local coordinate system of the object to be measured can be established. The y-axis is taken to pass through the origin and perpendicular to the x-axis. The z-axis is taken as passing through the origin and perpendicular to the x-axis and the y-axis, and the direction is determined according to the right-hand rule, which is well known to those skilled in the art. The object to be measured can have its own reference coordinate system, which is established by CAD drawing. For example, CAD drawings may have data to establish the origin, x-axis, y-axis, and z-axis. In order to place the CAD drawing in the reference frame of the laser tracker, or similarly, place the laser tracker in the reference frame of the CAD drawing, three transformation matrices are usually obtained. The transformation matrix is usually a 4X4 matrix, including a 3X3 matrix rotation matrix and a scaling component that describes the translation of the reference frame relative to other reference frames. In the above case, the three transformation matrices are multiplied together in a specific order to obtain a total transformation matrix, and the measured value or CAD value is transformed into a desired reference frame. The use of the transformation matrix is well known to those skilled in the art and will not be described here.

[0082] In addition to the inclination angle of the laser tracker and the object to be measured, the laser tracker also measures the three-dimensional coordinates of at least two retroreflector target points, by allowing the first retroreflector target point as the object to be measured The local origin of the object, and allows the direction from the first target point to the second target point to establish the local x-axis of the object to be measured, and the local coordinate system of the object to be measured can be established. If the inclinometer set on the laser tracker and the object to be measured respectively measure two vertical inclination angles and gravity

Vector, then the rotation method known to those skilled in the art can be used again to rotate the object to be measured to arrange two gravity vectors. Because there is only one possible rotation for the gravity vector that provides an appropriate correspondence between the local X-axis of the object to be measured and the X-axis defined by the CAD model, the ambiguity about the rotation angle of the gravity vector can be eliminated. As long as the three-dimensional coordinates of the two retroreflector target points measured by the laser tracker do not form a straight line consistent with the gravity vector, this method is effective.

[0083] Another way to observe the transformation between reference frames is to consider the number of degrees of freedom provided by the measurement values. For example, when the laser tracker measures the target point of the first retroreflector, it is said that the possible movement of the object to be measured is restricted in three degrees of freedom, because for the points on the object to be measured, the relationship between X, y and The first, second, and third degrees of freedom corresponding to the z-coordinate. Physically, this constraint fixes the position of the measuring point in space, but allows the object to be measured to rotate in any direction about the point. When the laser tracker measures the target point of the second retroreflector, it is said that the possible movement of the object to be measured is restricted in the additional two degrees of freedom, because the object to be measured no longer has a rotation at any of the three azimuth angles. The ability is instead constrained to rotate about a straight line connecting the first and second retroreflector target points. Therefore, three azimuth degrees of freedom are reduced to one azimuth degree of freedom. For the overall constraint of 5 degrees of freedom, the first measurement point constrains three translational degrees of freedom, and the second measurement point constrains two azimuth degrees of freedom. Because there is an unconstrained degree of freedom in this case, the total number of constrained and unconstrained degrees of freedom is 6.

[0084] In the case where the laser tracker and the inclinometer on the object to be measured respectively measure two inclination angles relative to the gravity vector, and the laser tracker measures the three-dimensional coordinates of only one target point, there is not enough information to completely constrain the object to be measured object. The two inclinometers constrain the two angles, but do not provide information about the rotation of the object to be measured (the rotation of the gravity vector). In other words, two inclinometers constrain two degrees of freedom. For the overall constraint of 5 degrees of freedom, the three-dimensional coordinate of a single target measured by the laser tracker provides the constraint of three degrees of freedom. Because full constraint requires 6 degrees of freedom, the measured value does not provide full constraint, and the object moves freely around the gravity vector.

[0085] For the case where the laser tracker and the inclinometer on the object to be measured respectively measure two inclination angles relative to the gravity vector, and the laser tracker measures the three-dimensional coordinates of the two target points, there is enough information to completely constrain the object to be measured Objects, as long as the two target points do not establish a straight line along the direction of the gravity vector. Through this measurement, it is said that the object to be measured is constrained in 6 degrees of freedom, as long as the two target points are not placed along the direction of the gravity vector.

[0086] In the case where two vectors are placed along the direction of the gravity vector, it is said that the object to be measured is constrained by 5 degrees of freedom, because there is not enough information to determine the orientation of the object to be measured with respect to the gravity vector. Note that the number of degrees of freedom cannot be determined by simply adding the number of degrees of freedom obtained by a single measurement. For example, the measurement of a single point constrains 3 degrees of freedom, but the measurement of two points constrains 5 degrees of freedom instead of 6 degrees of freedom. In addition, note that the two angular degrees of freedom provided by the laser tracker and the inclinometer on the object to be measured do not add the 5 degrees of freedom obtained by the laser tracker measurement of the two retroreflector target points to obtain 6 or 7 Degrees of freedom. This is because the two degrees of freedom provided by the inclinometer do not correspond to a basic group that is independent of the basic group of two target points measured by the laser tracker. In other words, the complete constraint of a single rigid body requires three translational degrees of freedom (for example, x, y, z) and three azimuth degrees of freedom (for example, pitch, roll, and yaw angle) constraints. In the above case, there is no restriction on the rotation about the gravity vector (usually called the deflection angle). In this application, the term "degrees of freedom" should be understood to mean independent degrees of freedom.

[0087] It should be understood that by rotating the azimuth axis and the zenith axis of the laser tracker, the target observed by the camera on the laser tracker may be in an area far away from the field of view (FOV) of the camera. For example, the FOV of one of the cameras on the laser tracker can be 30 degrees in the azimuth direction. However, the azimuth axis of the tracker can be rotated 360 degrees, so the effective F0V of the camera is increased to 360 degrees.

[0088] Embodiments of the present invention allow a measurement system (eg, laser tracker, target processing, SMR or other laser tracker target, computer system, measurement system software, and optionally, a handheld device connected to the measurement software or (Remote Control) Operators with limited training can optionally follow a set of prompts and instructions via a computer (for example, general-purpose computer 60) to set up the laser tracker, optionally place the required processing SMR on the part to be measured, and Optionally define the region of interest to be measured. Then the measurement system can automatically measure the target point and produce the result.

[0089] The embodiment of the present invention to help the operator achieve simpler and faster measurement is a method in which the laser tracker aims the beam at the desired measurement position at the object and prompts the operator to place the SMR at the desired position . For example, the operator can be prompted to place the retroreflector target in a magnetic nest on the object to be measured. As another example, the retroreflector may be placed in the wrong position, and the beam from the laser tracker can prompt the operator to move the misplaced target to the correct position. The hint can be done, for example, by sequentially moving the light beam from the first position containing the misplaced target to the second position of the target to be placed.

[0090] The guidance given by the light beam from the laser tracker also has advantages during the setup phase, in which the operator places the SMR at the designated position when the laser tracker measures the three-dimensional coordinates of the target position. This advantage is seen when the nominal size given on the CAD model does not correspond to the actual size of the object to be measured. If the accurate three-dimensional position of the target point is determined during the setting, the measurement time and measurement errors in the subsequent processing can be reduced.

[0091] The guidance of the operator's actions through the instructions of the light beam can help eliminate errors. For example, the software's test plan for the laser tracker can instruct the operator to measure points in a specific order. The results of this measurement can be saved and used to obtain the desired relationship-for example, the relationship between two reference frames, the length between two lines, or the angle between two planes. If the operator measures the initial point in the wrong order or measures the wrong point, the software will not get the expected value or get the wrong answer.

[0092] In the above case, the operator is guided to place the retroreflector target in a fixed position, which may be, for example, a magnetic nest or a machining hole. However, there is another important situation in which the operator measures the surface profile. This surface profile can be measured, for example to determine the flatness of the surface or the diameter of a ball, or two surfaces can be measured to determine the angle between the surfaces. As another example, the operator can measure a part of a tool that is configured to assemble a car or airplane. The laser tracker can be used to measure the surface profile to see if the surface is within the design tolerance. If not, the operator can be guided to modify the tool in an appropriate way-for example, it may be possible to wear material from an area. In all these cases where SMR is used to measure surface contours, by pointing out the area to be scanned, the software that controls the laser tracker can greatly simplify and speed up the procedure by the operator. This can be done by allowing the laser tracker to guide the beam to delimit the area to be scanned by the operator. Alternatively, the actual path that the operator will follow during the scan can be traced.

[0093] Laser trackers can also be used to assist in the assembly of complex structures. For example, it may be necessary to attach multiple components to the cockpit of the aircraft. In many cases, the cost-effective way to achieve this is to aim the beam and instruct the assembler to drill holes or perform other operations in the appropriate locations. After the components are attached, the operator can be instructed to scan the outline of the mounting part to confirm that the installation is carried out correctly. To aid in this measurement, one or more cameras can be used to identify the retroreflector on the object to be assembled. These retroreflectors can be used to move the laser tracker to the reference frame of the object to be assembled, so that the laser tracker can use the light beam from the tracker to guide the action of the assembler.

[0094] By rotating the azimuth axis or the zenith axis, one or more cameras on the laser tracker have the ability to measure all retroreflector targets in a large effective FOV, as described above. If the only targets reachable by the laser tracker are those on the object to be measured, the laser tracker can automatically determine the space area to be measured by observing the targets of the retroreflector. On the other hand, if the target occupies several objects and not all objects are of interest for the current measurement, then in some cases,

The operator must indicate the area to be measured. In one embodiment, the operator can indicate the area to be measured by delimiting the area of interest using a retroreflector. The operator can achieve this, for example, by performing four consecutive movements of the retroreflector target to indicate the upper, lower, left, and right ranges of the area. In another embodiment, the operator can manually move the load (or equivalent structure) of the laser tracker to indicate the beam at the upper, lower, left, and right edges of the area of interest. The operator can be instructed to make these movements through the software that controls the laser tracker, or the operator can give the posture to give the information without the need to be guided by a computer program to do so. These gestures may include, for example, moving the retroreflector target in a predetermined pattern in a specified time interval. As another example, the operator can express the desire to delimit the area by grabbing the load and moving the beam from the laser tracker directly downwards. The operator can follow this initial movement by moving the load to delimit the upper, lower, left, and right edges of the desired measurement area. In other cases, the software that controls the laser tracker can perform a target matching program, where the software recognizes a collection of retroreflector targets corresponding to the CAD model or the three-dimensional coordinate list of the target.

[0095] In the above discussion, the benefits of laser trackers using light beams to help operators perform measurements were emphasized. Consider the benefits of fully automatic measurement. A potential benefit is that, because of the speed of fully automatic measurement, additional targets can be added to the object to be tested without increasing the test time. By providing more points in each data set, the software can determine the desired geometric characteristics of the object to be measured faster with fewer potential errors. In addition, without the need for the user to manually move the SMR, the possibility of object displacement during the measurement phase is reduced through the measurement point set. This in turn reduces the possibility of measurement errors.

[0096] The potential advantage of a fully automatic measurement is that the order in which the measurement is performed can be optimized. When there are many target positions on the object to be measured, the operator can measure the target position according to the relative proximity of the points, because this is the fastest procedure for manual measurement. On the other hand, in a fully automated procedure, measurements can be performed in the order that produces the most accurate and robust measurement results. For example, the two points on the data line can be on opposite sides of the large object to be measured. The automatic test program can measure these widely distributed data points one by one to avoid drift and get the most accurate measurement results.

[0097] Another potential advantage of fully automatic measurement is the possibility of automatic retrofitting. It is often desirable to periodically measure the characteristics of tools used in product manufacturing. This periodic measurement helps ensure that the tool does not bend, the target does not move, and so on. If the object to be measured is raised, the software controlling the laser tracker will notice this during the periodic measurement. The software will call the automatic modification program accordingly, which reconstructs the new position of the raised target. In addition, the automatic modification procedure can reduce the requirement for rigid installation (to rigidly clamp the object to the tool). Lower rigidity requirements result in lower costs for very accurate, reusable tools for construction and operation.

[0098] Another example of automatic modification is for the case where the object to be measured is on the assembly line. Such an object may not be exactly in the same position after it has completed the circuit and has been returned to the laser tracker for inspection. The laser tracker can measure the reference point to reconstruct the relationship between the reference frame of the laser tracker and the reference frame of the object to be measured.

[0099] One of the capabilities that may be formed by the above-mentioned automatic measurement is the setting of desired accuracy values (which can be by the user) to drive designated operations and set thresholds for warnings and alarms. For example, the value set for the desired accuracy can drive: (1) the frequency and tolerance of stability check; (2) the comparison requirement of self-compensation relative to full aiming; (3) the frequency and tolerance of self-compensation; (4) The threshold of the number of measurement samples at each measurement point; (5) the limit of environmental temperature change before the compensation check; (6) the tolerance for the acceptable results of the arrangement and position movement; and (7) the frequency and tolerance of the drift check difference.

[0100] Alternatively, each of these values can be set individually. The matrix of values can be set based on different applications and operating conditions, and they can be saved and retrieved as a measurement profile.

[0101] Consider an example in which the setup procedure includes the cooperation of an operator instead of being fully automated. For the desired

To measure the position, the laser tracker 10 is aimed at the desired position on the object to place the SMRo. In the first embodiment, when placing the SMR in the beam, the operator clamps the SMR in his hand, so that the beam can lock the SMRo and SMR After being placed on an object (for example, on a magnetic nest), the laser tracker measures the three-dimensional coordinates and moves the beam to the next target position. In the second embodiment, the operator places the retroreflector on the object, such as a magnetic nest. If the beam does not lock the retroreflector immediately, the operator gives a signal by moving a hand in front of the retroreflector target, for example, causing the target to flash in the camera's field of view. The tracker searches for the SMR and quickly measures the SMR position. Then the tracker advances to the next nominal point and guides the operator where the target is placed on the object. The third embodiment is similar to the second embodiment, except that if the target is not found immediately, the laser tracker does not search. In contrast, when the operator moves a hand in front of the retroreflector target, the laser tracker guides the beam to the next target position. In the initial setup process, for example, by limiting the time of each measurement to approximately 0.1 second, it is acceptable to make all measurements relatively quickly.

[0102] A large number of retroreflector targets, possibly more than 100, can be used to measure points on the tool. In some cases, the operator may wish to put only a portion of the retroreflectors at a time (for example, 25 retroreflectors at a time) to save money on the purchase of retroreflectors. The measurement period is defined as the period during which the available retroreflector targets (for example, 25 targets) are set on the tool and measured by the laser tracker.

[0103] If the SMR has not been attached to the object to be measured, the operator either manually or uses the guidance provided by the laser tracker 10 to place the SMR on the object. Then, the tracker can perform stability and reference system checks. The stability check can be performed by measuring one or more points. In an embodiment, the tracker measures two or more points at the most boundary of the measurement volume together with the closest point in the center of the volume. The laser tracker 10 automatically takes a series of points with a shorter or longer duration (more samples) to determine the optimal number of samples to obtain the desired accuracy (the operator sets the number in the system). The system setting for point-by-point samples is set to this value. The system will have the option to recheck the stability after a certain period of time, the number of points measured at the beginning and/or end of each period. After the first measurement of the reference point (minimum of 3), they can be re-measured at the end of the cycle to check for movement, or they can be re-measured at the beginning of each cycle to redirect the laser tracker to the part, Correct any movement of objects that may be introduced by the operator when moving the SMR. A simpler and faster way to check for possible movement is to place a single point on the object and a second point elsewhere; for example, on the floor. These locations always include the SMR, and the measurement system can check them periodically throughout the measurement phase. One way is, except for each cycle In addition to the beginning and end of the measurement phase, inspections are performed at specific time intervals. A minimal implementation will measure these drift points at the beginning and end of each measurement phase.

[0104] The measurement system automatically measures all required points on a system-by-system setting. The user's light of the laser tracker can flash an LED pattern after measuring each point to warn the operator of the moving or failure point. If the point fails, the operator can abort the automatic measurement by waving his hand before any target in the FOV of the tracker. The camera system will register the interruption of the flash of a single target in response to the flashing light source 54 and suspend the measurement. The operator can keep the hand before the handicap so that it can be adjusted. Then the laser tracker is aimed at the desired point. The digital readout guides the operator to adjust the part where the tool is out of tolerance. When the adjustment is completed, the operator can give another posture (for example, move the hand before SMR), instruct the laser tracker to re-measure the points, and continue to measure the remaining points. By marking the SMR or physically moving the azimuth axis or zenith axis of the system, all measurement processing can be performed, so the operator does not need to use a remote control, mouse or keyboard.

[0105] Referring to FIGS. 5 and 6, regarding the object 500 to be measured by the laser tracker 10, the three-dimensional view of the laser tracker 10 of FIG. 1 or FIG. 2 along the first orientation and the second orientation is shown, and the laser tracker 10 The measurement of various target points (such as SMR 26) on the object 500 is automatically performed. The object 500 can be any type of larger object, such as a shelf, which is

Parts of a car assembly line. However, this is only exemplary; the object 500 may be any type of processed or finished product. As described above, the object 500 has a plurality of target points 26, such as SMR 26. According to an embodiment of the present invention, the plurality of target points are placed at various positions of the object 500. The SMR can also be placed on a component clamped by the object 500.

[0106] FIG. 5A shows multiple SMRs 26 at various positions on the object 500. In addition, the laser tracker 10 is shown to aim its laser beam 46 at these multiple SMRs 26. In addition, the cone 510 represents the field of view of the one or more cameras 52 and 58 of the laser tracker 10 when the camera (multiple cameras) observes a part of the object 500.

[0107] FIG. 5B is similar to FIG. 5A, but now the laser tracker 10 changes direction with respect to the object 500. In addition, some SMR 26 on the object 500 at the specific position in FIG. 5A has moved to the other on the object 500 in FIG. 5B position. In addition, the cones of the fields of view of the cameras (multiple cameras) 52 and 58 are in different orientations with respect to the object 500. This enables the camera (multiple cameras) 52.58 to capture other additional target points 26 on the object 500. In either of the two ways, the target can be moved to two different positions. On the assembly line, the shelf can be moved a small amount to allow changes in the perspective of the laser tracker, as shown in Figures 5 and 6. For stationary tools, the laser tracker can be moved to measure points that may be hidden from the field of view.

[0108] Due to the size of the object 500 to be measured and the desired accuracy, if not resolved, the ambient temperature of the object 500 may become a source of measurement errors. For example, metal structures expand when they become hot. In addition, the nominal value of the object (such as a CAD file) is usually set to a temperature where the controlled room is in the temperature range of 20 degrees Celsius or 68 degrees Fahrenheit. If the measured object is higher than this temperature, it will actually be larger. If you know the component material and temperature, it is common to adjust the difference by applying a scaling factor to the measurement job and adjusting the measurement data back to the design temperature, or by measuring the reference point and applying the scaling factor when changing the job.

[0109] In the automatic measurement phase (in which the reference point 26 is used and measured), the operator can always apply the scaling factor when changing the work through the setting instructions in the software. The problem with this example is that if the geometry of the object changes, bends, etc., the automatic scaling method can reduce this error by changing the scale of the work. The second method can use a material sensor placed on the object and allow the operator to input the expansion coefficient or material type. Based on these inputs, the system can determine the scale. However, the preferred method that an automated system can operate is to compare the two methods and warn the operator if any change exceeds the desired system accuracy. The operator can place one or more material sensors on the object. The system can check the ambient temperature via internal tracker sensors or external sensors. If the difference is large enough to cause the part to expand or contract during the measurement phase, the system warns the operator to allow the object to be immersed in the environment and delays the measurement until the object temperature stabilizes. The measurement task may include the type of material and/or the expansion coefficient of the material. The system measures reference points on the object and compares their values with nominal or expected values.

[0110] During the conversion process, the system calculates the scaling factor based on the conversion of the measurement to the nominal, and calculates the scale based on the material type and the material temperature sensor. If there is an unacceptable difference between the two scale calculations, the operator is warned and the measurement phase stops. This difference can indicate that one of the following conditions has occurred, and the system cannot measure and work as expected; (1) The material temperature sensor (multiple sensors) and/or the air temperature sensor (multiple sensors) may be defective and The wrong value is generated; (2) or a more general reason may be that the object geometry is deformed to the extent that the reference point 26 is no longer at the designed position on the object. When automatic scaling tends to hide these errors and introduce uncertainty or errors throughout the work, it is more difficult to detect in the current measurement phase. If there is an error in the reference point, the traditional whole work will be slightly shifted away from the nominal, and this will cause some points to fail incorrectly. If the highest accuracy is required, then during the measurement phase, additional inspections can be performed by the system to minimize expansion or contraction of the component.

[0111] In contrast, most automated systems can use the stereo camera 52 on the laser tracker 10 to determine the depth

And location to estimate the location of SMR 26. In the embodiment, the operator places the SMR 26 on the object 500 and manually aim them in the direction of the laser tracker 10. As prompted by the software, the operator manually moves the azimuth axis and the zenith axis of the tracker 10 to the relatively extreme points of the measurement volume to indicate the desired measurement volume. The software prompts the operator to move the tracker head and laser beam 46 to the rightmost point; then the operator moves the tracker head. When the movement stabilizes for a certain amount of time (for example, 2 seconds), the system records the position. The software prompts the user to move the tracker head to the leftmost, uppermost and lowermost edges of the desired volume.

[0112] If the indicated volume exceeds the range of the widest field of view of the camera system 52 on the tracker 10, the tracker performs a programmed sweep/surround view of the entire volume, looking for the SMR 26 or target. If needed, this programmed glance/surround will be repeated throughout the measurement phase to monitor the status of the SMR or find user input to the system. Using the stereo camera 52, the laser tracker 10 estimates the XYZ position of each point in the measurement volume. The measurement system software calculates the first approximation for the transformation between the tracker and the point set. Then the tracker aims at the desired point. If there is any point invisible from the measuring device, the tracker 10 flashes an error through the LED (not shown) on the front of the tracker, and then aims at the position where the target 26 missed, missed, or was confused by other objects. The tracker can be moved in a fixed pattern to make the position more visible to the operator. Once the point is corrected, the operator can mark the SMR 26, and the system will know the measurement location and continue processing. Also automatically, the tracker 10 aims and uses the camera system 52 or a conventional search system to locate and measure each target 26.

[0113] As mentioned above, when pointing the beam at a target location, it may sometimes be a good idea to move the beam in the pattern instead of aiming it at a fixed angle. For example, consider the situation where the position of the magnetic nest is separated from the top of the object to be measured. In this case, the beam directed directly at the target location (ie, the center of the retroreflector target when placed in the magnetic nest) can be seen by the operator because it can pass without hitting anything in its path object. By moving the beam in the pattern, the desired position of the SMR can be seen.

[0114] If the laser tracker 10 is configured with one or more wide field of view (WFOV) cameras and one or more narrow field of view (NFOV) cameras, the system can determine the general position of the SMR 26 and aim at the point 26 through the WFOV camera. If the laser beam 46 does not collide with the center of the target 26 and is close enough for the tracking system to lock the target, one or more of the following processes can be performed. The tracker can re-evaluate the position according to the WF0V camera and aim at the stationary point again. (2) The tracker can switch to the NF0V camera and recalculate the optical center of the target and aim at the calculated center and try to acquire the target through the tracking system. (3) If the tracker is equipped with the optical zoom function on the NF0V camera, and the NF0V camera cannot see the target after changing from the WF0V camera (WF0V position calculation causes the tracker to aim at a position with enough error for the NF0V camera (cannot see the SMR error) , NFOV camera can narrow the visible point of the target, and then calculate the optical center and correctly aim the tracker.

[0115] Any one of these processes can be repeated until the target is reacquired. The advantage is that compared with the traditional aiming and searching method using laser beam and position sensor, the combination of WFOV camera and NFOV camera (herein referred to as camera system) can be used. Faster.

[0116] In other embodiments of the present invention, another measurement procedure may be to compare the measurement result with the allowable tolerance under the guidance of the software. The laser tracker 10 can compare the nominal (CAD model) size between target points on the tool with the size measured by the laser tracker. If the error between the nominal size and the measured size exceeds the tolerance value, the tracker can take action. This action can be as simple as re-measuring the point or measuring the point for a longer period of time. The tracker can also perform double-sided measurement to ensure that there is no problem with the accuracy of the tracker. In the alternative, the action taken by the tracker could be to send an error message to the operator, beep, flash, or even shut down the production line until the operator checks the stability.

Qualitatively, make adjustments or, for example, replace defective targets.

[0117] The implementation of the double-sided test is described in, for example, US Patent No. 7,327,446 ('446) to Cramer et al., the entire contents of which are incorporated herein by reference. The tracker 10 performs double-sided measurement of one or more target points 26. If the obtained double-sided error exceeds the specified value (for example, as given on the manufacturer's data sheet), the next step may be for the tracker to perform a compensation procedure to improve the tracker's performance. There are two types of compensation procedures that are most commonly performed (although other procedures are also possible). These two procedures are the self-compensation procedure and the directional compensation procedure described in the '446 patent. Pointing compensation procedures include multiple double-sided measurements by pointing to the target, the target can be installed on the floor, on the base or on the object. After collecting the data from the pointing compensation, the tracker automatically corrects its internal parameters, thereby improving its measurement accuracy.

[0118] Another measurement procedure may be to check the stability of the measurement over time. For example, the tracker can measure a target point on the floor and another target point on the tool. If the relative position of the two target points changes with the measurement process, the tracker can alert the operator. Similarly, the tracker can measure the distance between three points on the tool, then return at the end of the measurement and re-measure these three points. If the relative positions of these points change, the validity of the entire measurement is questioned and additional measurements may be required.

[0119] Although the discussion mainly deals with the case where one or more cameras are placed on the load of the laser tracker, those skilled in the art should understand that these cameras can also be placed inside the laser tracker (for example, with the laser tracker). The optical axis of the instrument is coaxial), is set on the azimuth frame 14 of the laser tracker 10, or is completely separated from the laser tracker.

[0120] FIG. 6 is a block diagram showing a dimensional measurement electronic processing system 1500. The system 1500 includes a laser tracker electronic processing system 1510, surrounding elements 1582, 1584, 1586, a computer 1590, and other network components 1600, which are represented by clouds here. The exemplary laser tracker electronic processing system 1510 includes a main processor 1520, a load function electronic device 1530, an azimuth encoder electronic device 1540, a Zenith encoder electronic device 1550, a display and user interface (UI) electronic device 1560, and mobile storage hardware 1565. Radio frequency identification (RFID) electronic device and antenna 1572. The load function electronics 1530 includes multiple sub-functions, and the multiple sub-functions include 6D0F electronic device 1531, camera electronic device 1532, ADM electronic device 1533, position detector (PSD) electronic device 1534, and grade electronic device 1535. Most sub-functions have at least one processor unit, such as a digital signal processor (DSP) or a field programmable gate array (FPGA). The electronic units 1530, 1540, and 1550 are separated because of their position in the laser tracker, as shown in the figure. In an embodiment, the load function 1530 is located in the load, the azimuth encoder electronics are located in the azimuth assembly, and the zenith encoder electronics 1550 are located in the zenith assembly.

[0121] Many types of peripherals are possible, but three devices are shown here: a temperature sensor 1582, a 6DOF probe 1584, and a personal digital assistant 1586 (such as a smart phone). The laser tracker can communicate with peripherals through various means, including wireless communication with cooperative targets (such as 6D0F probe 1584) via the antenna 1572, through the distance and angle readings of the vision system (such as a camera) and through the laser tracker.

[0122] In an embodiment, an independent communication bus extends from the main processor 1520 to each electronic unit 1530.540, 1550, 1560, 1565, and 1570. Each communication line may have, for example, three serial lines, including a data line, a clock line, and a frame line. The frame line indicates whether the electronic unit should pay attention to the clock line. If it indicates that attention should be paid, the electronic unit reads the current value of the data line at each clock signal. The clock signal may correspond to the rising edge of the clock pulse, for example. In an embodiment, the information is transmitted in the form of data packets on the data line. In an embodiment, each data packet includes an address, a digital value, a data message, and a checksum. The address indicates where to direct the data message in the electronic unit. The location may correspond to a processor subroutine in the electronic unit, for example. The numeric value indicates the length of the data message. The data message contains data or instructions to be executed by the electronic unit. The checksum is used to compare the error transmitted via the communication line.

The numeric value that minimizes performance.

[0123] In an embodiment, the main processor 1520 sends the information packet to the load function electronic device 1530 via the bus 1610, sends it to the position encoder electronic device 1540 via the bus 1611, and sends it to the Zenith encoder electronic device via the bus 1612. 1550, sent to the display and UI electronic device 1560 via the bus 1613, sent to the mobile storage hardware 1565 via the bus 1614, and sent to the RFID and wireless electronic device 1570 via the bus 1616.

[0124] In an embodiment, the main processor 1520 also sends synch (synchronization) pulses to each electronic unit via the synchronization bus 1630 at the same time. The sync pulse provides a way to synchronize the values collected by the measurement function of the laser tracker. For example, the azimuth encoder electronic device 1540 and the Zenith encoder electronic device 1550 latch their encoder values as soon as they receive the synchronization pulse. Similarly, the load function electronic device 1530 latches the data collected by the electronic device contained in the load. When the synchronization pulse is given, the 6D0F, ADM, and position detector all latch the data. In most cases, cameras and inclinometers collect data at a slower rate than the sync pulse rate, but they can latch data with multiple sync pulse periods.

[0125] The laser tracker electronic processing system 1510 may communicate with an external computer 1590, or it may provide calculation, display, and UI functions in the laser tracker. The laser tracker communicates with the computer 1590 via a communication link 1606. The communication link 1606 may be, for example, an Ethernet line or a wireless connection. The laser tracker may also communicate with other elements 1600 represented by the cloud via a communication link 1602, which may include one or more cables, such as Ethernet cables, and one or more wireless connections. An example of the element 1600 is another three-dimensional test instrument-for example, the communication link 1604 between the CMMo computer 1590 and the element 1600, which can be reset by a laser tracker, can be wired (for example, Ethernet) or wireless. The operator located at the remote computer 1590 can connect to the Internet represented by the cloud 1600 through an Ethernet or wireless line, and then connect to the main processor 1520 through an Ethernet or wireless line. In this way, the user can control the actions of the remote laser tracker.

[0126] FIG. 7 is a flowchart showing step 700 in an embodiment for performing measurement by the system. Step 705 is to provide a system including a collection of retroreflector targets and a laser tracker. The set of retroreflector targets includes at least three retroreflector targets, namely the first target, the first target and the third target, and these targets are not arranged in a straight line. The laser tracker is in the first reference frame, which is shown as the reference frame 30 in FIGS. 1, 5 and 6. In the embodiment, the origin of the reference frame of the laser tracker is the gimbal point 22 of the laser tracker. The X, y, and z axes of the first reference frame are fixed with respect to the tracker's environment, but generally refer to tracker characteristics (such as rotation direction). The laser tracker includes a structure, a first light source, an absolute distance meter, a first angle converter, a second angle converter, a tracking system, a first camera, a second light source, and a processor. The structure is rotatable about the first axis and the second axis. In an embodiment, the first axis is the azimuth axis, and the second axis is the zenith axis. In an embodiment, the structure is to support the load of the optical component. In another embodiment, the structure is a mirror that deflects the light to send the light out of the laser tracker in the desired direction. The first light source that generates the first light beam may be a laser, a super light emitting diode, or other types of light sources. The absolute distance meter cooperates with the first light source to measure the absolute distance. The light from the first light source can be used to measure that the light travels through the air to the retroreflector target and returns to the tracker at the speed of light. Time spent. The method of measuring the time of flight may include a phase measurement method, a pulse time of flight method, or any other type of absolute distance measurement method. In an embodiment, the first angle converter and the second angle converter may be angle encoders that measure the azimuth angle and the zenith angle. The tracking system is used to keep the first beam centered on the retroreflector target. The position of the retroreflector is the position relative to the reflection of the beam. For example, in a cube corner retroreflector, light is reflected symmetrically about the vertices of the cube corners, which are the points related to the intersection of three mutually perpendicular surfaces. In many cases, the point where the light reflects symmetrically is at the center of the sphere. For example, in the spherical-mounted retroreflector type, the vertex of the open-air cube corner is placed in the center of the steel ball. In this case, the tracking system of the laser tracker keeps the first beam to the retroreflector target

The center is the center. However, the retroreflector target does not have to be in the center of the ball. Even better, the retroreflector can be directly attached to the object to be measured, Instead of placing it in the ball. In this case, the term "center" is meant to indicate the point where the first beam symmetrically reflects the associated retroreflector, even if it does not indicate the center of any object. The tracking system of the laser tracker can keep a part of the reflected light centered on the position detector in the laser tracker. The position detector is, for example, a position sensitive detector or a photosensitive array. The laser tracker includes a first camera. In the embodiment, the first camera is installed on the outer surface of the load of the tracker, and the load can rotate about a first axis and a second axis. In other embodiments, the first camera may be arranged inside the laser tracker, and may observe a scene outside the laser tracker, and the scene is centered on the optical axis of the laser tracker. In other embodiments, the first camera can be set relative to other positions on or inside the laser tracker. The first camera includes a first lens and a first photosensitive array. The first lens produces an image of an object outside the laser tracker on the first photosensitive array. The second light source emits a second light beam, and in most cases the second light source is closest to the first camera. The light is transmitted to the retroreflector target, which is part of the set of retroreflector targets. A part of the second light beam is reflected off the retroreflector and returns to the first camera, and the first camera images the reflected light on the first photosensitive array. The processor may be provided in the laser tracker, in the partner electronic unit 50, in the external unit 60, or in a combination of locations. The processor may include a combination of processing elements, the processing elements including micro Processor, digital processing unit, field programmable gate array and memory. The processor is configured to operate the laser tracker.

[0127] Step 710 is to store a list of nominal coordinates for the first target, the second target, the third target, and the at least one additional point. The nominal coordinates are the three-dimensional coordinates given in the second frame of reference. The second reference frame is associated with the object to be measured, or is associated with the structure to which the object to be measured is attached. Examples of the second reference frame 40 are shown in FIGS. 1, 5 and 6. Generally, the X, y, and z axes of the second frame of reference can be rotated about the X, y, and z axes of the first frame of reference.

[0128] Step 715 is to capture a part of the light emitted by the second light beam and reflected away from the first target, the second target and the third target on the first photosensitive array.

[0129] Step 720 is to obtain the position of the light spot on the photosensitive array according to a part of the light reflected off the first target, the second target and the third target. The light spot position may be, for example, the centroid of the light spot for the first target, the second target, and the third target.

[0130] Step 725 is to respectively determine the correspondence between the first spot position, the second spot position, and the third spot position on the first photosensitive array and the nominal coordinates of the first target, the second target, and the third target. This correspondence relationship can be obtained in various ways, for example according to the method described in the appended claims. One such method includes observing possible correspondences in the allowable range of the orientation of the second reference frame through the first reference frame. Another method involves using two (stereo) cameras on the laser tracker, using the triangulation method. Another method involves using a single tracker camera, but rotating the tracker to two different orientations. In this way, the two images obtained on the photosensitive array of the camera are used to determine the correspondence. It is also possible to measure with the first camera in the front sight and rear sight modes, and use the image obtained on the first photosensitive array to determine the correspondence. The relative positions of the first reference frame and the second reference frame can be changed, and the pattern of light spots obtained on the first photosensitive array can be used to determine the corresponding relationship. For example, the second reference frame can be associated with the mobile frame, as shown in Figures 5 and 6, so the first camera can obtain two different images, just like in the different relative positions of the first reference frame and the second reference frame . In an embodiment, a general formula used to determine the correspondence between the first, second, and third light spots on the photosensitive array and the nominal coordinates of the first target, the second target, and the third target can be adopted. The mathematical method involves constructing a transformation matrix, transforming the coordinates from reference frame 2 to reference frame 1 or vice versa, as described above and in the appended claims. For the image obtained by the photosensitive array, the points on the array can be projected from the position on the photosensitive array to the target space through the perspective center of the lens. In this way, the light spots on the first photosensitive array can be converted into angles. If the second photosensitive array is available, use the known distance between the first photosensitive array and the second photosensitive array to pass

Using methods known to those skilled in the art, a triangulation program can be used to determine the position of each of the three targets. If only a single camera is available, the triangulation method can still be applied by obtaining images of the front and rear sights, because the position of the camera is flipped to the opposite side of the tracker's optical axis when changing from the front sight to the rear sight mode. The distance between the camera position in the front sight and rear sight mode is known, so this procedure is equivalent to the stereo triangulation procedure. Similarly, by only rotating the tracker structure to two different angles (about the first axis, the second axis, or both), two different views can be obtained, and a method similar to the triangulation program can be used, as described above As described in '033. Among them, it is known that the constraint method of the approximate relative orientation between the first reference frame and the second reference frame generally does not allow a direct solution for each of the three-dimensional coordinates of the first target, the second target, and the third target. In most cases, it makes it possible to localize the position, which is good enough to draw the correspondence between the three light points and the nominal coordinates of the first, second, and third targets.

[0131] Step 730 is to guide the first light beam to the first target based at least in part on the position of the first light spot and the nominal coordinates of the first target, and to use an absolute distance meter, a first angle converter, and a second angle converter Measure the three-dimensional coordinates of the first target. As described in step 720, some methods of obtaining the corresponding relationship provide three-dimensional coordinates with respect to the first frame of reference, so it is simple and straightforward to guide the laser beam to the first target, the second target, and the third target. In the case where the direction is based on the constraints between the first reference frame and the second reference frame, the best direction of the first goal, the second goal, and the third goal may not be known with high accuracy; The distance can get the direction. The resulting direction is usually sufficiently close to the best direction to be able to capture the target, for example by the method described in the appended claims. The measured three-dimensional coordinates are in the first reference frame, which is the reference frame of the laser tracker.

[0132] Step 735 is the same as step 730, and is only applied to the second target instead of the first target. Step 740 is the same as step 735, and only applies to the third target instead of the first target.

[0133] Step 745 is to determine the three-dimensional coordinates of at least one additional point in the first reference frame based at least in part on the measured three-dimensional coordinates of the first, second, and third targets and the nominal coordinates of the at least one additional point. This is a mathematical step, which can be performed, for example, by obtaining a transformation matrix. The transformation matrix realizes the calculation of any nominal coordinates as three-dimensional coordinates in the first frame of reference (tracker). Using methods known to those skilled in the art, the three-dimensional coordinates obtained in steps 725.730 and 735 are sufficient to determine the transformation matrix.

[0134] Step 750 is to store the three-dimensional coordinates of at least one additional point. The coordinates may be stored in an electronically readable medium, a computer memory, or a microprocessor, for example. Step 755 is the termination of the method with step 700.

[0135] FIG. 8 is a flowchart showing step 800 in an embodiment for performing measurement by the system. Step 800 follows point A labeled 755 in FIG. 7. Step 805 is to guide the light beam to at least one additional point. The laser tracker can perform this step automatically.

[0136] Step 810 is to place the selected retroreflector target and intercept the first beam. One way to achieve this is for the operator to move the hand-held selected retroreflector target to the first beam. The second way to achieve this is to place the selected retroreflector target on a nest mounted on the object to be measured, such as a magnetic nest. If the three-dimensional coordinates of at least one additional point are known accurately enough, the first laser beam can be guided, good enough to capture at least a part of the beam through the clear aperture of the selected retroreflector target.

[0137] Step 815 is to guide the first beam to the center of the selected retroreflector target. This step is performed by the tracking system of the laser tracker. Step 820 is to measure the three-dimensional coordinates of the selected retroreflector target using the absolute distance meter, the first angle transformer and the second angle transformer. The method 800 terminates in step 825.

[0138] FIG. 9 is a flowchart showing step 900 in an embodiment for measurement by the system. Step 900 follows

The point Ao marked 755 in FIG. 7 step 905 is to guide the light beam to at least one additional point.

[0139] Step 910 is to move the first light beam to the first pattern in the space, where the first pattern is closest to at least one additional point. This first pattern is usually called a search pattern. As an example, the light beam can start at an initial position and then move outward in a spiral pattern.

[0140] Step 915 is to detect the light beam through the tracking system of the laser tracker. This can happen when the first light beam reflected off the retroreflector hits the position detector. Through this detection indication of the light by the position detector, the first light beam has intercepted the clear hole of the retroreflector target.

[0141] Step 920 is to guide the first beam to the center of the selected retroreflector target. As mentioned above, the center in this context represents the position of the relevant retroreflector target that reflects symmetrically with respect to the beam. The term "center" in this context does not necessarily mean the physical center of the retroreflector target.

[0142] Step 925 is to measure the three-dimensional coordinates of the selected retroreflector target using the absolute distance meter, the first angle converter and the second angle converter. The method 900 terminates in step 930.

[0143] FIG. 10 is a flowchart showing step 1000 in an embodiment for performing measurement by the system. Step 1000 Follow the point Ao marked 755 in Fig. 7. Step 1005 is to provide a third camera and a fourth light source. The third camera includes a third lens system and a third photosensitive array. The field of view of the third camera is smaller than that of the first camera. In the field of view, the fourth light source provides the fourth light beam.

[0144] Step 1010 is to capture a part of the light emitted by the fourth light source and reflected off the first target, the second target and the third target on the third photosensitive array. Images of the first target, the second target, and the third target have been obtained by the first camera. The third camera is used to collect additional measurement results. In some cases, the information obtained from the first camera can be used to manipulate the laser tracker to a position where the second camera can see the first target, the second target, or the third target.

[0145] Step 1015 is to obtain the position of the light spot on the photosensitive array according to a part of the light reflected off each target of the first target, the second target and the third target. The position of this light spot can be obtained, for example, as the centroid of each light spot.

[0146] Step 1020 is to respectively determine the correspondence between the first spot position, the first spot position, and the third spot position on the third photosensitive array and the nominal coordinates of the first target, the second target, and the third target. relationship. The method for determining the correspondence is the same as the above method, but the third camera with a narrower field of view than the first camera provides relatively more accurate information. The method 1000 terminates at step 1025.

[0147] FIG. 11 is a flowchart showing step 1100 in an embodiment for measurement by the system. Step 1100 follows point A labeled 755 in FIG. 7. Step 1105 is to guide the first light beam to multiple attachment points, the multiple attachment points including the first attachment point, and the multiple attachment points indicate actions to be taken by the operator. In this way, the laser tracker can guide the actions of the operator.

[0148] FIG. 12 is a flowchart showing step 1200 in an embodiment for performing measurement by the system. Step 1200 is followed by the point Bo marked 825 in Fig. 8. Step 1205 is to measure according to the inspection plan. A typical inspection plan may include various points to be measured. Some points can be on the surface of the object, while other points can be in the nest. Some points can be measured separately, while other points are measured in a scan pattern on a specified surface.

[0149] FIG. 13 is a flowchart showing step 1300 in an embodiment for performing measurement by the system. Step 1300 follows point A labeled 755 in FIG. 7. Step 1305 is to guide the first beam to at least one additional point. Step 1310 is to perform an assembly operation at the position of the first beam. Assembly operations may include drilling holes, sanding, plastering, milling, or any other operations intended to modify or add objects. For example, the first light beam may indicate the location on the object to be drilled.

[0150] FIG. 14 is a flowchart showing step 1400 in an embodiment for performing measurement by the system. Step 1400

Step 1405 following the point Bo marked 825 in Fig. 8 is to provide an inspection plan, and measure the inspection point with a laser tracker. Step 1410 is to attach at least one retroreflector target to the object to be measured. This kind of retroreflector target effectively acts as a drift monument to realize the stability check of the system. Step 1415 is to provide the maximum allowable movement to the three-dimensional coordinates of at least one retroreflector target attached to the object to be measured. The maximum allowable movement is a numerical value provided by the user based on the required stability. Step 1020 is to measure the three-dimensional coordinates of at least one retroreflector target attached to the object to be measured, and the measurement is performed at the first time and at the second time. Step 1025 is to determine the first change in the three-dimensional coordinates of the at least one retroreflector target from the first time to the second time. In a highly stable system, these coordinates change by a small amount. If the object to be measured or the laser tracker is hit, the measurement result changes suddenly, which introduces errors. Similarly, if the ambient temperature changes significantly, the size of the object will change, the performance of the tracker will decrease, or the nature of the air through which the first beam propagates will change. Any change in these changes will reduce the accuracy of the measurement. Step 1030 is to take an action when the first change exceeds the maximum allowable movement. The action may include measuring at least three retroreflectors on the object to be measured to reconstruct the three-dimensional inspection point coordinate. It may also include notifying the operator that the first change has exceeded the maximum allowable movement. This can prompt the operator to recompensate the laser tracker, check the stability of the object to be measured and the laser tracker, or take other steps. The method 1400 terminates at step 1435.

[0151] FIG. 15 is a flowchart showing step 1700 in an embodiment for measurement by the system. Step 1700 follows point A labeled 755 in FIG. 7. Step 1705 is to provide the maximum allowable deviation. This is the value provided by the user. Step 1710 is to provide the coefficient of thermal expansion (CTE) and the reference temperature of the object to be measured. As an example, if the material is steel, 0^ of 11.5 microns/m/£ can be provided. The reference temperature can be a common value of 20°C. Step 1715 is to place the first reference retroreflector and the second reference retroreflector on the object to be measured. At the reference temperature, there is a first distance between the first reference retroreflector and the second reference retroreflector. Step 1720 is to measure the temperature of the object to be measured. Step 1725 is to calculate the first temperature difference by subtracting the reference temperature from the measured temperature of the object to be measured. Step 1730 is by multiplying the first temperature difference by the thermal expansion coefficient, Calculate the zoom factor. The unit of the value thus given is, for example, microns/meter. In other words, the scaling factor is a dimensionless quantity. Step 1735 is to measure the 3D coordinates of the first reference retroreflector and the second reference retroreflector using the absolute distance meter, the first angle transformer and the first angle transformer. Step 1740 is to calculate a second distance extending from the measured 3D coordinates of the first reference retroreflector to the measured 3D coordinates of the second reference retroreflector. Step 1745 is to calculate the third distance by subtracting the first distance from the second distance. Step 1750 is to calculate the fourth distance by multiplying the first distance by the scaling factor. Step 1755 is to calculate the deviation value by subtracting the third distance from the fourth distance. Step 1760 is to take an action when the deviation value exceeds the maximum allowable deviation. The action is to issue an alarm or measure the coordinates of at least some retroreflector targets in the set of retroreflector targets, and reconstruct a reference frame for the object based on these data. The purpose of step 1700 is to check the consistency of the thermal length compensation to directly measure the length difference. If the length change does not match, it is possible that the temperature measurement is invalid, the CTE value is not given correctly, or there are some other problems. Through this problem identification, additional steps can be taken.

[0152] As understood by those skilled in the art, the solution of the present invention can be specifically implemented as a system, a method, or a computer program product. Therefore, the solution of the present invention can take the form of a complete hardware embodiment, a complete software embodiment (including firmware, resident software, microcode, etc.), or an embodiment combining software and hardware solutions, and all of them can be generalized here. Ground is called "circuit", "module" or "system". In addition, the solution of the present invention may take the form of a computer program embodied in one or more computer readable media, and the computer readable program code may be embodied on the computer readable medium.

[0153] Any combination of one or more computer readable media may be utilized. The computer-readable medium may be a computer-readable signal medium or a computer-readable storage medium. The computer-readable storage medium may be, for example, electronic, magnetic, optical, electromagnetic,

Infrared or semiconductor system, equipment or device or any suitable combination of the foregoing, but not limited to this. More specific examples (non-exhaustive list) of computer readable media may include the following: electrical connections with one or more wires, portable computer disks, hard disks, random access memory (RAM), read-only memory (ROM), Erasable programmable read-only memory (EPROM or flash memory), optical fiber, portable compact disk read-only memory (CD-ROM), optical storage device, magnetic storage device, or any suitable combination of the foregoing. In the context of this document, a computer-readable storage medium may be any tangible medium, which may contain or store a program used by the instruction execution system, device, or device or a program related to the instruction execution system, device, or device. [0154] Any combination of one or more computer readable media may be utilized. The computer-readable medium may be a computer-readable signal medium or a computer-readable storage medium. The computer-readable storage medium may be, for example, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, device or device, or any suitable combination of the foregoing, but is not limited thereto. More specific examples (non-exhaustive list) of computer readable media may include the following: electrical connections with one or more wires, portable computer disks, hard disks, random access memory (RAM), read-only memory (ROM), Erasable programmable read-only memory (EPROM or flash Storage), optical fiber, portable compact disk read-only memory (CD-ROM), optical storage device, magnetic storage device or any suitable combination of the foregoing. In the context of this document, a computer-readable storage medium may be any tangible medium, which may contain or store a program used by the instruction execution system, device, or device or a program related to the instruction execution system, device, or device. [0155] The computer-readable signal medium may include, for example, a data signal propagated in baseband or as a part of a carrier wave, in which computer-readable program code is embodied. This propagated signal can take any of a variety of forms, including but not limited to electromagnetic, optical, or any suitable combination thereof. The computer-readable signal medium may be any computer-readable medium that is not a computer-readable storage medium, and that can transfer, propagate, or transmit the program used by the instruction execution system, device, or device or the program related to the instruction execution system, device, or device .

[0156] The program code embodied on a computer-readable medium can be transmitted using any suitable medium, including but not limited to wireless, wired, fiber optic cable, RF, etc., or any suitable combination of the foregoing.

[0157] The computer program code used to perform the operations of the solution of the present invention can be written in any combination of one or more programming languages, including object-oriented programming languages (such as Java, Smalltalk, C++, C#, etc.) and Traditional procedural programming languages (such as "C" programming language or similar programming languages). The program code can be executed entirely on the user's computer, partly executed on the user's computer as a stand-alone software package, partly executed on the user's computer and partly on a remote computer, or entirely executed on the remote computer or server. In the latter case, the remote computer can be connected to the users computer through any type of network, including a local area network (LAN) or a wide area network (WAN), or can be connected to an external computer (for example, by using the Internet service providers Internet ). The solution of the present invention is described with reference to flowchart illustrations and/or block diagrams of methods, devices (systems) and computer program products according to embodiments of the present invention. It should be understood that each block of the flowchart description and/or block diagram and the combination of the blocks in the flowchart description and/or block diagram can be implemented by computer program instructions.

[0158] These computer program instructions can be provided to the processor of a general-purpose computer, a special-purpose computer, or other programmable data processing equipment to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing equipment can be used to generate A method for implementing the functions/actions specified in the flowchart and/or block diagram or block. These computer program instructions can also be stored in a computer-readable medium. The computer-readable medium can guide a computer, other programmable data processing equipment, or other devices to operate in a specific manner. Therefore, the instructions stored in the computer-readable medium produce the terms of manufacture, Including instructions for realizing the functions/actions specified in the flowchart and/or block diagrams or blocks.

[0159] Computer program instructions can also be loaded into a computer, other programmable data processing equipment or other devices, causing a series of operational steps to be executed on the computer, causing other programmable devices or other devices to produce computer-implemented

Processing, therefore, instructions executed on a computer or other programmable device provide processing to implement the functions/actions specified in the flowcharts and/or block diagrams or blocks.

[0160] Any flowcharts and block diagrams in the drawings illustrate the configuration, functions, and operations of possible implementations of systems, methods, and computer program products according to various embodiments of the present invention. In this regard, each block in the flowchart or block diagram may represent a module, segment, or part of code, including one or more executable instructions for implementing the specified logical function (multiple functions). It should be understood that, in some alternative implementations, the functions noted in the blocks may occur out of the order noted in the drawings. For example, two blocks shown in succession may actually be executed substantially simultaneously, or sometimes the blocks may be executed in the reverse order, depending on the functions involved. In addition, it should be noted that each block described in the block diagram and/or flowchart and the combination of the blocks in the block diagram and/or flowchart description can be implemented by a dedicated hardware-based system or a combination of dedicated hardware and computer instructions. The system executes the specified function or action.

[0161] Although the preferred embodiments have been shown and described, various modifications and substitutions can be made without departing from the spirit and scope of the present invention. Therefore, it should be understood that the present invention has been described by way of illustration and not limitation.

[0162] Therefore, the currently disclosed embodiments should be regarded as illustrative rather than restrictive in any respect, and the scope of the present invention is pointed out by the appended claims rather than the foregoing description, and therefore, falls into the claims All changes in the meaning and scope of the equivalent of will be covered.

[0163] According to the above description, the embodiments of the present invention disclose but are not limited to the following technical solutions:

[0164] Scheme 1. A method for measuring through a system, the method (700) comprising the steps:

[0165] A system (705) including a collection of retroreflector targets (26, 27, 28) and a laser tracker (10) is provided, the collection of retroreflector targets includes at least three non-collinear retroreflector targets (27) The at least three non-collinear retroreflector targets include a first target, a second target, and a third target. The laser tracker in the first reference frame (30) is fixed with respect to the tracker environment, so The laser tracker has a structure (15), a first light source, an absolute distance meter (1533), a first angle converter (1540), a first angle converter (1550), a tracking system (1534), and a first camera ( 52, 400), a first light source (54, 401) and a processor (1520, 50, 60), the structure can be rotated about the first axis (20) and the second axis (18), the first light source generates and The first light beam (46) coordinated by the absolute distance meter, the first angle transducer measures the first rotation angle (71) about the first axis, and the second angle transducer measures the first angle of rotation about the second axis. The second rotation angle (72) of the shaft, the tracking system is configured to move the first beam to the center of any retroreflector target in the retroreflector target set, the first camera including a first A lens system (402) and a first photosensitive array (404), the second light source provides a second light beam (440), and the processor is configured to operate the laser tracker;

[0166] stored for the first target, the second target, the third target and at least one additional point (26,

29) A list (710) of nominal coordinates, where the nominal coordinates are three-dimensional coordinates in the second frame of reference (40);

[0167] capturing a part of the light emitted by the second light beam and reflected off the first target, the second target, and the third target on the first photosensitive array (715);

[0168] Obtain the position of the light spot on the photosensitive array (720, 42) according to a part of the light reflected off each of the first target, the second target and the third target (720, 42);

[0169] Determine the positions of the first light spot, the second light spot, and the third light spot on the first photosensitive array and the names of the first target, the second target, and the third target, respectively Correspondence between coordinates (725);

[0170] based at least in part on the position of the first light spot and the nominal coordinates of the first target, directing the first light beam to the first target (730);

[0171] Using the absolute distance meter, the first angle converter and the second angle converter to measure the three-dimensional coordinates of the first target (730);

[0172] directing the first light beam to the second target based at least in part on the position of the second light spot and the nominal coordinates of the second target (735);

[0173] using the absolute distance meter, the first angle transducer and the second angle transducer to measure the three-dimensional coordinates of the second target (735);

[0174] based at least in part on the position of the third light spot and the nominal coordinates of the third target, directing the first light beam to the third target (740);

[0175] using the absolute distance meter, the first angle converter and the second angle converter to measure the three-dimensional coordinates of the third target (740);

[0176] Determine at least one of the first reference frames based at least in part on the measured three-dimensional coordinates of the first target, the second target, and the third target and the nominal coordinate of the at least one additional point The three-dimensional coordinates of the additional point (745); and

[0177] The determined three-dimensional coordinates of the at least one additional point are stored (750).

[0178] Scheme 2. The method according to Scheme 1, further comprising the steps:

[0179] guiding the first light beam to the at least one additional point (805);

[0180] placing the selected retroreflector target to intercept at least a part of the first light beam, and the selected retroreflector target is selected from any retroreflector target in the set of retroreflector targets (810);

[0181] directing the first beam to the center of the selected retroreflector target (815); and

[0182] Using the absolute distance meter, the first angle converter and the second angle converter, measure the three-dimensional coordinates of the selected retroreflector target (820).

[0183] Scheme 3. The method according to scheme 2, wherein the step of placing the selected retroreflector target to intercept at least a part of the first light beam comprises a step selected from the following group, the group comprising:

[0184] moving the selected retroreflector target to intercept at least a part of the first light beam; and

[0185] The selected retroreflector target is placed in a fixed nest, and the fixed nest is located at a position that intercepts at least a part of the first light beam.

[0186] Scheme 4. The method according to Scheme 1, further comprising the steps:

[0187] guiding the first light beam to the at least one additional point (905);

[0188] moving the first light beam into a first pattern in space, the first pattern being closest to the at least one additional point (910);

[0189] Detect the presence of the first light beam through the tracking system (915);

[0190] directing the first beam to the center of the selected retroreflector target (920); and

[0191] Using the absolute distance meter, the first angle converter and the second angle converter to measure the three-dimensional coordinates of the selected retroreflector target (925).

[0192] Scheme 5. The method according to Scheme 1, further comprising the steps:

[0193] A third camera and a fourth light source (1005) are provided, the third camera (58) includes a third lens system and a third photosensitive array, and the field of view of the third camera is smaller than that of the first camera. Field, the fourth light source (56) provides a fourth light beam;

[0194] On the third photosensitive array, the light emitted by the fourth light source and reflected away from the first target and the

Part of the light rays (1010) of the second target and the third target;

[0195] Obtain the position of the light spot on the photosensitive array according to a part of the light reflected away from each of the first target, the second target and the third target (1015); and

[0196] Determine the positions of the first light spot, the second light spot, and the third light spot on the third photosensitive array and the names of the first target, the second target, and the third target, respectively Correspondence between coordinates (1020).

[0197] Scheme 6. The method according to scheme 1, wherein the first light-sensitive array is captured by the second light beam emitted and reflected away from the first target, the second target, and the third The step of part of the light of the target further includes a step selected from the following group, the group including:

[0198] placing the laser tracker on a shelf so that the first photosensitive array simultaneously obtains the positions of the light spots for the first target, the second target, and the third target;

[0199] Rotate the first camera and the second light source to multiple orientations, so that for the first target, the second target, and the third target, the first photosensitive array is in the Some of these positions get some light spot positions; and

[0200] Move the selected retroreflector in the set of retroreflectors to delimit a space region including the first target, the second target, and the third target, the space region being defined by The laser tracker is determined by tracking the selected retroreflector target or by following the movement of the selected retroreflector target on the first photosensitive array.

[0201] Scheme 7. The method according to scheme 1, wherein the step of providing a system including a collection of retroreflector targets and a laser tracker further includes providing a second camera and a third light source, the second camera including a second A lens system and a second photosensitive array, the third light source provides a third light beam, and the processor in the laser tracker is further configured to calculate the three-dimensionality of any retroreflector target in the set of retroreflector targets The calculated three-dimensional coordinates are based at least in part on the first image on the first photosensitive array and the second image on the second photosensitive array, and the first image and the second image are respectively responsive to the The light rays emitted by the second light source and the third light source are obtained, and the light rays from the first light source and the first light source are reflected by a retroreflector target in the set of retroreflector targets.

[0202] Solution & The method according to solution 1, wherein the positions of the first light spot, the second light spot, and the third light spot on the first photosensitive array are determined separately from the first target, the The correspondence between the nominal coordinates of the second target and the third target includes a step selected from the following groups, and the group includes:

[0203] based at least in part on the allowable relative orientation range between the first frame of reference and the second frame of reference and the nominal coordinates of the first target, the second target, and the third target, To determine the corresponding relationship;

[0204] In response to the irradiation of the first target, the second target, and the third target by light from the second light source, the first target from the first photosensitive array is collected at a first time. Group of images; changing one of the first rotation angle and the second rotation angle, and responding to the first target, the second target, and the first target, the second target, and the first target by the light from the second light source Illuminating three targets, collecting a second set of images from the first photosensitive array at a second time; and determining the position of the first light spot, the position of the second light spot on the first photosensitive array, and The corresponding relationship between the position of the third light spot and the nominal coordinates of the first target, the second target, and the third target, and the determination is based at least in part on the first set of images and the nominal coordinates. The second set of images; and

[0205] In response to the irradiation of the first target, the second target, and the third target by light from the second light source, the third target from the first photosensitive array is collected at a third time. Group of images; changing the position of the second frame of reference relative to the first frame of reference, and responding to the first frame of reference through the light from the second light source

The illumination of the target, the second target and the third target, collecting a fourth set of images from the first photosensitive array at a fourth time; and determining the position of the first light spot on the photosensitive array , The corresponding relationship between the second spot position and the third spot position and the nominal coordinates of the first target, the second target, and the third target, and the determination is based at least in part on The third group of images and the fourth group of images.

[0206] Scheme 9. The method according to scheme 1, wherein a list of nominal coordinates for the first target, the second target and the third target and at least one additional point is stored, the nominal coordinates The step of being the three-dimensional coordinates in the second frame of reference further includes one of the following steps:

[0207] extracting the nominal coordinates from the CAD model; and

[0208] The nominal coordinates are measured by a 3D measuring instrument.

[0209] Scheme 10. The method according to scheme 1, further comprising the step of guiding the first light beam to a plurality of additional points, the plurality of additional points including a first additional point, the plurality of additional points indicating The action to be taken by the operator (1105).

[0210] Scheme 11. The method according to Scheme 10, wherein the action to be taken by the operator includes at least one of the following

[0211] picking up a selected retroreflector target, the selected retroreflector target being designated by the plurality of additional points;

[0212] moving the selected retroreflector target along the direction indicated by the plurality of additional points, capturing the first light beam by the retroreflector, and using the absolute distance meter and the first angle converter And the second angle converter, measuring the three-dimensional coordinates of at least one point;

[0213] observing a pattern formed by the plurality of additional points, capturing the first light beam by the retroreflector, and measuring three-dimensional points along the pattern; and

[0214] Observe the pattern formed by the plurality of additional points, interpret the points as a gesture command, and take an action indicated by the gesture command.

[0215] Scheme 12. The method according to Scheme 1, wherein the step of determining the three-dimensional coordinates of the at least one additional point further includes the step of:

[0216] Calculate a transformation matrix, the transformation matrix is used to transform any three-dimensional coordinates in the second reference frame into any three-dimensional coordinates in the first reference frame, the calculation is based at least in part on the first The nominal coordinates of the target, the second target, and the third target; and

[0217] Calculating the three-dimensional coordinates of the at least one additional point based at least in part on the transformation matrix and the nominal coordinates of the at least one additional point.

[0218] Scheme 13. The method according to scheme 1, wherein the step of providing a system including a collection of retroreflector targets and a laser tracker includes providing at least one cube-corner retroreflector from the collection of retroreflector targets For the retroreflector target, the cube corner retroreflector has three reflective surfaces perpendicular to each other.

[0219] Option 14. The method according to Option 1, wherein the step of providing a system including a collection of retroreflector targets and a laser tracker includes providing at least one retroreflector target from the set of retroreflector targets as a spherical mount The retroreflector mounted on the spherical surface has a cube corner retroreflector embedded in the surface of the sphere.

[0220] Scheme 15. The method according to Scheme 1, wherein the step of providing a system including a collection of retroreflector targets and a laser tracker includes providing at least one retroreflector target from the collection of retroreflector targets as located on the ball The reflective point at the center of the surface.

[0221] Scheme 16. The method according to Scheme 2, further comprising the step of measuring according to the inspection scheme (1205). [0222] Scheme 17. The method according to scheme 16, wherein the step of measuring according to the inspection plan is further included in the

Steps to automatically perform measurement in the presence of operator intervention.

[0223] Solution 1 & The method according to claim 16, wherein the step of measuring according to the inspection plan further includes the step of: moving the first beam to guide the operator to move the selected retroreflector target, thereby according to the inspection plan Take measurements.

[0224] Scheme 19. The method according to scheme 16, wherein the step of measuring according to the inspection scheme further comprises: detecting when the operator places the retroreflector target in the wrong position, and guiding the operator to select The retroreflector target is moved to the correct position, and the laser tracker moves the first beam to indicate to the operator the correct position of the selected retroreflector target.

[0225] Scheme 20. The method according to Scheme 1, further comprising the steps:

[0226] directing the first light beam to the at least one additional point (1305); and

[0227] Perform an assembly operation at the position of the first beam (1310).

[0228] Aspect 21. The method according to aspect 20, wherein the step of performing an assembly operation includes drilling a hole in an object at the position of the first beam.

[0229] Scheme 22. The method according to Scheme 2, further comprising the steps:

[0230] Providing an inspection plan (1405) for measuring inspection points by the laser tracker;

[0231] Attach at least one retroreflector target to the object to be measured (1410);

[0232] Provide a maximum allowable movement to the three-dimensional coordinates of the at least one retroreflector target attached to the object to be measured (1415);

[0233] measuring the three-dimensional coordinates of the at least one retroreflector target attached to the object to be measured, the measurement being performed at a first time and at a second time (1420);

[0234] determining a first change in the three-dimensional coordinates of the at least one retroreflector target from the first time to the second time (1425); and

[0235] When the first change exceeds the maximum allowable movement, an action is taken (1430), and the action is one of the following:

[0236] measuring at least three retroreflectors on the object to be measured to reconstruct the three-dimensional coordinates of the inspection point, and

[0237] Notifying the operator that the first change has exceeded the maximum allowable movement.

[0238] Scheme 23. The method according to Scheme 1, further comprising the steps:

[0239] Provide the maximum allowable deviation (1705);

[0240] Provide a thermal expansion coefficient to the object to be measured (1710);

[0241] Provide a reference temperature (1710);

[0242] The first reference retroreflector and the second reference retroreflector are placed on the object to be measured, and at the reference temperature, the first reference retroreflector and the second reference retroreflector Between is the first distance (1715);

[0243] measuring the temperature of the object to be measured (1720);

[0244] Calculate the first temperature difference by subtracting the reference temperature from the measured temperature of the object to be measured (1725);

[0245] Calculating a scaling factor by multiplying the first temperature difference by the thermal expansion coefficient (1730);

[0246] using the absolute distance meter, the first angle converter and the second angle converter to measure the three-dimensional coordinates of the first reference retroreflector (1735);

[0247] using the absolute distance meter, the first angle converter, and the second angle converter to measure the three-dimensional coordinates of the second reference retroreflector (1735);

[0248] calculating a second distance extending from the measured three-dimensional coordinates of the first reference retroreflector to the measured three-dimensional coordinates of the second reference retroreflector (1740);

[0249] Calculate a third distance by subtracting the first distance from the second distance (1745);

[0250] Calculate the fourth distance by multiplying the scaling factor by the first distance (1750);

[0251] Calculate the deviation value by subtracting the third distance from the fourth distance (1755); and

[0252] When the deviation value exceeds the maximum allowable deviation, an action is taken, the action is to issue an alarm, or to measure the three-dimensional coordinates of at least some retroreflector targets in the set of retroreflector targets, and according to these Data, reconstruct the frame of reference for the object to be measured (1760).

[0253] Scheme 24. The method according to Scheme 16, wherein the step of measuring according to the inspection scheme includes the steps:

[0254] Obtain the nominal coordinates of the target point, the nominal coordinates are obtained from data provided in computer-aided drawing (CAD), and the CAD data is transformed into the first frame of reference;

[0255] providing the selected retroreflector target as a spherical surface mounted retroreflector, the spherical surface mounted retroreflector having a cube corner retroreflector embedded in the spherical surface, the spherical surface having a first radius;

[0256] placing the selected retroreflector target at the position of the target point, and the retroreflector target is either held against the target point or placed on a magnetic nest representing the target point;

[0257] using the absolute distance meter, the first angle converter, and the second angle converter to measure the three-dimensional coordinates of the selected retroreflector target;

[0258] calculating the three-dimensional coordinates of the measured target point based at least in part on the measured three-dimensional coordinates of the selected retroreflector target and the first radius;

[0259] Calculate the first difference between the measured three-dimensional coordinates of the target point and the nominal coordinates of the target point; and

[0260] An indication of the first difference is provided.

[0261] Aspect 25. The method according to aspect 24, wherein the step of providing an indication of the first difference comprises: providing a warning if the first difference exceeds a first allowable difference.

[0262] Scheme 26. The method according to scheme 16, wherein the step of measuring according to the inspection scheme includes the steps of: performing a double-sided test to obtain a double-sided error, and if the double-sided error exceeds the maximum allowable double-sided error value, Then provide language 1=1.

[0263] Aspect 27. The method according to aspect 16, wherein the step of measuring according to the inspection plan includes the step of measuring the three-dimensional coordinates of two target points, and if the relative position of the two target points exceeds the maximum allowable target change value , Provides a warning.