Three-dimensional coordinate scanner and method of operation

The subject matter disclosed herein relates to a three-dimensional coordinate scanner, in particular a triangular ranging scanner having a large number of data acquisition methods.

Acquisition of three-dimensional coordinates of an object or environment is known. Various techniques can be used, such as flight time or triangular ranging methods. A flight time system, such as a laser tracker, total station, or flight time scanner, directs a ray, such as a laser beam, to a retroreflector target or a spot on the surface of an object. An absolute rangefinder is used to determine the distance to a target or spot based on the length of time it takes for the light to reach the target or spot and then return. By moving the laser beam or target on the surface of the object, the coordinates of the object are confirmed. Flight time systems have the advantage of having relatively high accuracy, but in some cases flight time systems usually have to measure each point on the surface individually, so some other systems. Is slower than.

In contrast, scanners that use triangular ranging to measure 3D coordinates have a linear optical pattern (such as a laser beam from a laser beam probe) and an area-covering optical pattern (such as structured light). ) Is projected onto the surface. By mounting the camera and the projector on a common frame, for example, the camera is fixedly coupled to the projector. The light emitted from the projector is reflected by the surface and detected by the camera. Since the camera and the projector are arranged in a fixed relationship, the distance to the object can be determined using the principle of trigonometry. Compared to coordinate measuring devices that use tactile probes, triangular ranging systems offer the advantage of being able to quickly acquire coordinate data over a large area. When used here, the collection result of the three-dimensional coordinate values provided by the triangular ranging system is called point cloud data or simply point cloud.

Several problems prevent the acquisition of high-precision point cloud data when using a laser scanner. These include, for example, changes in the reflectance of the surface of the object or changes in the angle of incidence of the surface with respect to projected light, resulting in changes in the level of light received by the camera image plane, low resolution near edges such as the edges of holes. , Including, but not limited to, multi-path interference. In some cases, the operator is unaware of the problem or unable to resolve it. In these cases, missing or defective point cloud data results.

<p num="0005"> Therefore, although existing scanners are suitable for their intended purpose, there remains a need for improvement, especially in terms of providing scanners that can adapt to inappropriate conditions to improve data point acquisition.</p>

<p num="0006"><u style="single">The present invention is a non-contact optical three-dimensional measuring device, which is an assembly including a first projector, a first camera, a second projector, and a second camera, the first projector, the first camera, and the above. The second projector and the second camera are in a fixed relationship with each other, and the first projector has a first light source and emits a first light having at least one pattern to the surface of an object. A first projector is configured, the first camera having a first lens and a first photosensitive array, receiving a first portion of the first light reflected on the surface and generating a corresponding first signal. As described above, the first camera is configured, the first camera has a first field of view, the first field of view is the first viewing angle region of the first camera, and the second projector has a second light source. Then, the second projector is configured to emit the second light to the surface of the object, the second camera has the second lens and the second photosensitive array, and the second camera is reflected by the surface. The second camera is configured to receive a second portion of light and generate a corresponding second signal, the second camera has a second field of view, and the second field of view is the second of the second camera. The first is electrically coupled to the assembly, the first projector, the second projector, the first camera, and the second camera, which are two viewing angle regions and whose second field of view is different from that of the first field of view. Collecting the first signal at a time point and collecting the second signal at a second time point different from the first time point, and at least partially based on the first signal, a tertiary of the first point on the surface. A processor that executes computer-executable program code that performs operations including determining the original coordinates and determining the three-dimensional coordinates of a second point on the surface based at least in part on the second signal. And, and when executed by the processor, the existence of the multi-path interference is determined, and when the multi-path interference is present, the third time between the first time point and the second time point is described. At a point in time, a computer run that performs operations, including moving the assembly from a first position to a second position.The processor is further configured to execute possible program code.</u>According to one aspect of the present invention, a non-contact optical coordinate measuring device is provided. Non-contact optical three-dimensional is an assembly that includes a projector, a first camera, and a second camera, in which the projector, the first camera, and the second camera are fixed to each other, and the projector and the first camera are connected to each other. A first distance is provided between them, a second distance is provided between the projector and the second camera, the projector has a light source, and the projector emits a first light having one of a plurality of spatial change patterns of the object. It is configured to radiate to the surface, the first camera has a first lens and a first photosensitive array, and the first camera receives the first part of the first light reflected on the surface and corresponds to the corresponding first. It is configured to generate one digital signal, the first camera has the first field of view, the first field of view is the first viewing angle region of the first camera, the second camera is the second lens and the second photosensitive array. The second camera is configured to receive the second part of the first light reflected on the surface and generate a corresponding second digital signal, and the second camera has a second field of view. Executed by the assembly, the projector, the processor electrically coupled to the projector, the first camera and the second camera, and the processor, where the second field of view is the second viewing angle region of the second camera and the second field of view is different from the first field of view. When this is done, the first digital signal is collected at the first time point, and the second digital signal is collected at the second time point different from the first time point, based on the first digital signal and the first distance at least partially. Includes a computer-readable medium that determines the three-dimensional coordinates of a first point on a surface and determines the three-dimensional coordinates of a second point on a surface based at least in part on a second digital signal and a second distance.</p><p num="0007"> The present invention<u style="single">In related technology</u>, A method for determining three-dimensional coordinates on the surface of an object is provided. This method provides an assembly that includes a projector, a first camera, and a second camera, in which the projector, the first camera, and the second camera are fixed to each other, and the projector and the first camera A first distance is provided between them, a second distance is provided between the projector and the second camera, the projector has a light source, and the projector has a first light on the surface that has one of a plurality of spatial change patterns. Configured to radiate, the first camera has a first lens and a first photosensitive array, and the first camera is configured to receive the first portion of the first light reflected on the surface. One camera has a first field of view, the first field of view is the first viewing angle region of the first camera, the second camera has a second lens and a second photosensitive array, and the second camera is on the surface. It is configured to receive the second part of the reflected first light, the second camera has a second field of view, the second field of view is the second viewing angle region of the second camera, and the second field of view is the second. A first light that provides an assembly that is different from one field, provides a processor that is electrically coupled to a projector, a first camera, and a second camera, and has a first pattern selected from multiple spatial change patterns. Is radiated from the projector to the surface as the first example, the first image of the surface is acquired by the first camera in the first example, the corresponding first digital signal is transmitted to the processor, and the first image on the surface is obtained. Determining the first set of three-dimensional coordinates of a point, determining the first set based at least partially on the first pattern, the first digital signal, and the first distance, and the quality of the first set. Is to perform a diagnostic procedure to evaluate and determine the second pattern of the first light selected from a plurality of spatial change patterns, the second pattern based at least in part on the results of the diagnostic procedure. The pattern is judged, the first light having the second pattern is emitted from the projector to the surface as the second example, and the second image of the surface is acquired by the second camera in the second example to obtain the corresponding second signal. To send to the processor and determine the second set of three-dimensional coordinates of the second point on the surface.</p><p num="0008"> These and other advantages and features will be more apparent from the following description, which is interpreted with the drawings.</p><p num="0009"> The subject matter considered to be the invention is pointed out in detail and is explicitly claimed in the last claim of the specification. The above and other features and advantages of the present invention will be apparent from the following detailed description when interpreted with the accompanying drawings.</p>

<figref num="1">It is a schematic top view of the scanner according to the embodiment of this invention.</figref><figref num="2">It is a flow chart which shows the method of operating the scanner of FIG.</figref><figref num="3">It is a schematic top view of the scanner according to another embodiment of the present invention.</figref><figref num="4">It is a flow chart which shows the method of operating the scanner of FIG.</figref><figref num="5A">It is the schematic of the element of the laser scanner by one Embodiment.</figref><figref num="5B">It is a flow chart which shows the method of operating the scanner by one Embodiment.</figref><figref num="6">It is a schematic top view of the scanner according to another embodiment of the present invention.</figref><figref num="7">It is a flow chart which shows the method of operating the scanner by one Embodiment.</figref><figref num="8A">It is a perspective view of the scanner used together with the remote probe device by embodiment of this invention.</figref><figref num="8B">It is a perspective view of the scanner used together with the remote probe device by embodiment of this invention.</figref><figref num="9">It is a flow chart which shows the method of operating the scanner of FIG.</figref><figref num="10">It is the schematic top view of the scanner by one Embodiment.</figref><figref num="11">It is a flow chart which shows the method of operating the scanner of FIG.</figref><figref num="12">It is a flow chart which shows the diagnostic method by one Embodiment.</figref>

In the detailed description, embodiments of the present invention will be described as examples, along with advantages and features, with reference to the drawings.

Embodiments of the present invention provide the advantage of increasing the reliability and accuracy of the three-dimensional coordinates of the data point cloud acquired by the scanner. Embodiments of the present invention provide the advantage of detecting anomalies in acquired data and automatically adjusting the operation of the scanner to obtain the desired result. Embodiments of the present invention provide the advantage of detecting anomalies in acquired data and instructing the operator on areas where additional data acquisition is required. Still further embodiments of the invention provide the advantage of detecting anomalies in acquired data and instructing the operator when additional data acquisition can be acquired with a remote probe.

The scanner device acquires the three-dimensional coordinate data of the object. In one embodiment, the scanner 20 shown in FIG. 1 has a housing 22 that includes a first camera, a second camera, and a projector 28. The projector 28 emits light 30 onto the surface 32 of the object 34. In an exemplary embodiment, the projector 28 uses a visible light source that illuminates the pattern generator. Visible light sources can be, for example, lasers, superluminescent diodes, incandescent light, xenon lamps, light emitting diodes (LEDs), or other light emitting devices. In one embodiment, the pattern generator is a chrome-on-glass slide with a structured light pattern etched. The slide can have a single pattern or multiple patterns that move from position to position as needed. The slide can be placed in the operating position manually or automatically. In other embodiments, the source pattern is Texas Instruments. Reflected by Digital Micromirror Devices (DMDs), Liquid Crystal Display (LCDs), Liquid Crystal on Silicon (LCOS) Devices, such as Digital Light Processing Projectors (DLPs) manufactured by Corporation, and similar devices used in conduction mode rather than reflection mode. Or it can be conducted light. The projector 28 may further include a lens system 36 that modifies the emitted light to cover the desired area.

In one embodiment, the projector 28 can be configured to radiate structured light into the area 37. As used herein, "structured light" refers to a two-dimensional pattern of light projected onto an area of an object that conveys information that can be used to determine the coordinates of points on the object. In one embodiment, the structured light pattern contains at least three non-collinear pattern elements placed within the area. Each of the three non-collinear pattern elements conveys information that can be used to determine the point coordinates. In another embodiment, a projector is provided that can be configured to project a linear pattern along with an area pattern. In one embodiment, the projector is a digital micromirror device (DMD) configured to switch back and forth between the two. In one embodiment, the DMD projector may sweep straight lines or sweep points in a raster pattern.

In general, there are two types of structured light patterns: coded light patterns and uncoded light patterns. When used here, the coded light pattern is one that obtains three-dimensional coordinates of the illuminated surface of an object by acquiring a single image. The coded light pattern allows the point cloud data to be acquired and recorded while the projection device is moving relative to the object. One type of coded light pattern includes a set of linearly arranged elements (such as geometric shapes), of which at least three are non-collinear. Such pattern elements are recognizable due to their arrangement.

In contrast, the uncoded structured light pattern used here is a pattern that does not allow measurement by a single pattern. A series of uncoded light patterns are sequentially projected and imaged. In this case, it is usually necessary to hold the projector fixed to the object.

It should be recognized that the scanner 20 can use either coded or uncoded structured optical patterns. Structured light patterns can include the patterns disclosed in Jason Geng's journal article "DLP-based Structured Light 3D Imaging Techniques and Applications" published in SPIE Bulletin No. 7923. In addition, in some embodiments described below, the projector 28 conducts patterned sweepline or sweep point light. The linear and point light that is swept is more advantageous than the area light in identifying some type of anomaly, such as multipath interference. Automatically sweeping straight lines while the scanner is stationary is also advantageous in that it provides a more uniform sampling of surface points.

The first camera 24 includes a photosensitive sensor 44 that produces a digital image / display of area 48 within the field of view of the sensor. The sensor can be a charge-coupled device (CCD) type sensor, or, for example, a complementary metal oxide semiconductor (CMOS) type sensor having an array of pixels. The first camera 24 may further include, but is not limited to, other components such as the lens 46 and other optical elements. The lens 46 has an associated first focal length. The sensor 44 and the lens 46 work together to define the first field of view "X". In an exemplary embodiment, the first field of view "X" is 16 degrees (0.28 inches per inch).

Similarly, the second camera 26 includes a photosensitive sensor 38 that produces a digital image / display in an area 40 within the field of view of the sensor. This sensor can be a charge-coupled device (CCD) type sensor, or, for example, a complementary metal oxide semiconductor (CMOS) type sensor having an array of pixels. The second camera 26 may further include, but is not limited to, the lens 42 and other components, such as other optics. The lens 42 has an associated second focal length, which is different from the first focal length. The sensor 38 and the lens 42 work together to define the second field of view "Y". In an exemplary embodiment, the second field of view "Y" is 50 degrees (0.85 inches per inch). The second field of view Y is larger than the first field of view X. Similarly, area 40 is larger than area 48. It should be recognized that a large field of view allows fast acquisition of a given area of the object surface 32 to be measured, but if the photosensitive arrays 44,38 have the same number of pixels, the field of view The narrower the value, the higher the resolution.

In the exemplary embodiment, the projector 28 and the first camera 24 are arranged in a fixed relationship at an angle such that the sensor 44 can receive the light reflected from the surface of the object 34. Similarly, the projector 28 and the second camera 26 are arranged in a fixed relationship at an angle at which the sensor 38 can receive the light reflected from the surface 32 of the object 34. Since the projector 28, the first camera 24, and the second camera 26 have a fixed geometric relationship, the distance and coordinates of points on the surface can be determined by the trigonometric relationship. The fields of view (FOVs) of cameras 24 and 26 are shown as non-overlapping in FIG. 1, but the FOVs may be partially or completely overlapped.

The projector 28 and the cameras 24 and 26 are electrically coupled to the control device 50 mounted in the housing 22. The control device 50 may include one or more microprocessors, a digital signal processor, a memory, and a signal conditioning circuit. The scanner 20 may further include an actuator (not shown) that is manually activated by the operator to initiate operation and data acquisition by the scanner 20. In one embodiment, the control device 50 performs image processing for determining the X, Y, Z coordinate data of the point cloud representing the surface 32 of the object 34. The coordinate data can be stored locally, for example in a volatile or non-volatile memory 54. The memory can be removable, for example a flash drive or memory card. In another embodiment, the scanner 20 has a communication circuit 52 that causes the scanner 20 to transmit coordinate data to the remote processing system 56. The communication medium 58 between the scanner 20 and the remote processing system 56 may be wired (Ethernet®, etc.) or wireless (Bluetooth, IEEE 802.11, etc.). In one embodiment, the coordinate data is determined by the remote processing system 56 based on the acquired image transmitted by the scanner 20 through the communication medium 58.

Relative motion is possible between the object surface 32 and the scanner 20 as indicated by the bidirectional arrow 47. There are several methods by which such relative motion is performed. In one embodiment, the scanner is a handheld scanner to which an object 34 is fixed. Relative motion is performed by moving the scanner on the surface of the object. In another embodiment, the scanner is mounted on a robotic end effector. When the robot moves the scanner on the surface of the object, the robot makes a relative motion. In another embodiment, the scanner 20 or object 34 is mounted on a mobile mechanical mechanism, such as a gantry coordinate measuring machine or an articulated arm CMM. Relative motion is performed by moving the mechanical mechanism when moving the scanner 20 on the surface of the object. In some embodiments, the movement is performed by the action of the operator, and in other embodiments, the movement is performed by a mechanism under computer control.

Now, referring to FIG. 2, the operation of the scanner 20 by the method 1260 is explained. As shown in block 1262, the projector 28 first radiates a structured light pattern into area 37 of surface 32 of object 34. The light 30 from the projector 28 is reflected from the surface 32 as the reflected light 62 received by the second camera 26. The three-dimensional profile of the surface 32 affects the image of the pattern captured by the photosensitive array 38 in the second camera 26. Using information collected from one or more images of one or more patterns, the controller 50 or remote processing system 56 uses the information between the pixels of the photosensitive array 38 and the pattern of light emitted by the projector 28. Judge one-to-one correspondence. Using this one-to-one correspondence, the principle of trigonometry is used to determine the three-dimensional coordinates of a point on surface 32. The acquisition of this 3D coordinate data (point cloud data) is shown in block 1264. By moving the scanner 20 across the surface 32, a point cloud is created for the entire object 34.

During the scanning process, controller 50 or remote processing system 56 may detect undesired conditions or problems with point cloud data as shown in block 1266. Methods for detecting such problems are described below with respect to FIG. The problem detected can be, for example, an error in the point cloud data in a particular area or its absence. Errors or absences in this data can result from too little or too much light reflected from this area. Under or over reflected light can occur, for example, on an object surface 32 as a result of a high or variable angle of incidence of light 30 onto the object surface 32, or as a result of a low reflectance (black or transparent) material or glossy surface. It can result from the difference in reflectance of. A point on an object can have an angle that produces a very bright specular reflectance known as glint.

Another possible reason for errors or absence of point cloud data, the solution in the region having an abrupt change in small features, sharp edges or depth, is the lack of Zodo. Such a lack of resolution can be the result of holes, for example.

Another possible reason for point cloud data error or absence is multipath interference. Normally, the rays from the projector 28 collide with points on the surface 32 and are scattered over an angular range. The scattered light is imaged in a small spot of the photosensitive array 38 by the lens 42 of the camera 26. Similarly, the scattered light can be imaged by the lens 46 of the camera 24 in a small spot on the photosensitive array 44. Multipath interference occurs when the light that reaches a point on the surface 32 is not only the light beam from the projector 28, but the secondary light is reflected by another part of the surface 32. Such secondary light can interfere with the accurate determination of the three-dimensional coordinates of this point by disturbing the pattern of light received by the photosensitive arrays 38,44. Methods for identifying the presence of multipath interference are described in this application with reference to FIG.

If the controller determines that there is no problem with the point cloud in block 1266, the procedure ends. Otherwise, a decision as to whether the scanner will be used in manual or automatic mode is made in block 1268. If the mode is manual, the operator is guided by block 1270 to move the scanner to the desired position.

There are many methods in which the operator directs the desired movement. In one embodiment, the indicator light on the scanner body indicates a desired movement direction. In another embodiment, light is projected onto the surface that indicates the direction in which the operator should move. In addition, the color of the projected light can indicate whether the scanner is too close or too far from the object. In another embodiment, the display gives instructions about the area on which the operator projects light. Such a display can be a graphic display of point cloud data, a CAD model, or a combination of the two. The display can be presented on a computer monitor, or a display built into a scanning device.

In any of these embodiments, a method of determining the approximate position of the scanner is desired. In one case, a joint angle encoder could be used to mount the scanner on an articulated arm CMM that determines the position and orientation of the scanner mounted at the end. In another case, the scanner includes an inertial sensor installed inside the device. Inertia sensors can include, for example, gyroscopes, accelerometers, and magnetometers. Another method of determining the approximate position of the scanner is to irradiate an object or its surroundings with photographic measurement dots provided as marker points. In this way, the scanner's wide-angle FOV camera can determine the approximate position of the scanner with respect to the object.

In another embodiment, the CAD model on the computer screen points to the area where additional measurements are desired, and the operator moves the scanner appropriately by matching the features on the object with the features on the scanner. By updating the CAD model on the screen as the scan takes place, the operator can get quick feedback as to whether the desired area of the part has been measured.

After the operator moves the scanner into place, measurements are taken at block 1272 by the small FOV camera 24. Visualizing a relatively small area on block 1272 improves the resolution of the resulting 3D coordinates and provides a good ability to reveal features such as holes and edges.

Since the narrow-angle FOV camera visually recognizes a relatively narrow area than the wide-angle FOV camera, the projector 28 can illuminate a relatively narrow area. This is advantageous for eliminating multipath interference, as the object is provided with relatively few irradiation points that can reflect light and return it to the object. Narrowing the irradiation area can facilitate exposure control to obtain the optimum amount of light for a given reflectance and angle of incidence of the object under inspection. In block 1274, the procedure ends in block 1276 when all points have been collected. Otherwise continue.

In an embodiment in which the modes after block 1268 are automated, in block 1278 the automation mechanism moves the scanner to the desired position. In some embodiments, the automation mechanism has a sensor that provides information about the relative position of the scanner and the object to be inspected. For embodiments where the automation mechanism is a robot, the angle transducer in the robot joint provides information about the position and orientation of the robot end effector used to hold the scanner. For embodiments in which the object is moved by another type of automation mechanism, a linear encoder or a variety of other sensors may provide information about the relative position of the object to the scanner.

After the automation mechanism moves the scanner or object into place, block 1280 makes a three-dimensional measurement with a small FOV camera. Block 1282 repeats such measurements until all measurements are complete and the procedure ends at block 1284.

In one embodiment, the projector 28 changes the structured light pattern when the scanner switches from data acquisition by the second camera 26 to the first camera 24. In another embodiment, the same structured light pattern is used in both cameras 24,26. In yet another embodiment, the projector 28 radiates a pattern formed by sweep lines or points when data is acquired by the first camera 24. After acquiring the data on the first camera 24, the process continues the scan using the second camera 26. This process continues until the operator scans the desired area of the part.

Although the process of FIG. 2 is shown as a linear or sequential process, it should be recognized that in other embodiments, one or more steps of the shown figure can be performed in parallel. In the method shown in FIG. 2, this method requires first measuring the entire object and then performing a more detailed measurement according to the evaluation of the acquired point cloud data. Alternative use of the scanner 20 begins by measuring the detailed or critical region using a camera 24 with a small FOV.

It should also be recognized that providing a method of changing a camera lens or projector lens as a method of changing the FOV of a camera or projector in a scanning system is a common practice in existing scanning systems. However, such changes are time consuming and generally require an additional correction step in which an artifact such as a dot plate is placed in front of the camera or projector to determine the aberration correction parameters of the camera or projector system. And. Therefore, scanning systems that provide two cameras with different FOVs, such as cameras 24 and 26 in Figure 1, offer significant advantages in scanner measurement speed and feasibility in fully automated mode.

Another embodiment for a scanner 20 having a housing 22 that includes a first coordinate acquisition system 76 and a second coordinate acquisition system 78 is shown in FIG. The first coordinate acquisition system 76 includes a first projector 80 and a first camera 82. Similar to the embodiment of FIG. 1, the projector 80 emits light 84 to the surface 32 of the object 34. In an exemplary embodiment, the projector 80 uses a visible light source that illuminates the pattern generator. Visible light sources can be lasers, superluminescent diodes, incandescent light, light emitting diodes (LEDs), or other light emitting elements. In one embodiment, the pattern generator is a chrome-on-glass slide with a structured light pattern etched. The slide can have a single pattern or multiple patterns that move from position to position as needed. The slide can be placed in the operating position manually or automatically. In other embodiments, the source pattern is Texas Instruments. Reflected or reflected by a digital micromirror device (DMD) such as a Digital Light Processing Projector (DLP) manufactured by Corporation, a liquid crystal display (LCD), a liquid crystal on silicon (LCOS) device, or a similar device used in conduction mode instead of reflection mode. It can be conducted light. The projector 80 may further include a lens system 86 that changes the emitted light to have the desired focal characteristics.

The first camera 82 includes a photosensitive array sensor 88 that produces a digital image / display in an area 90 within the field of view of the sensor. The sensor can be a charge-coupled device (CCD) type sensor, or, for example, a complementary metal oxide semiconductor (CMOS) type sensor having an array of pixels. The first camera 82 may further include other components, such as, but not limited to, the lens 92 and other optics. The first projector 80 and the first camera 82 are arranged at a fixed angle so that the first camera 82 can detect the light 85 from the first projector 80 reflected by the surface 32 of the object 34. Since the first camera 92 and the first projector 80 are arranged in a fixed relationship, the above-mentioned trigonometry principle can be used to determine the coordinates of a point on the surface 32 in the area 90. For clarity, FIG. 3 is drawn assuming that the first camera 82 is near the first projector 80, but it should be recognized that the camera may be located near the opposite side of the housing 22. Is. It is expected that the accuracy of 3D measurement will be improved by further separating the first camera 82 and the first projector 80.

The second coordinate acquisition system 78 includes a second projector 94 and a second camera 96. The projector 94 has a light source that can include a laser, a light emitting diode (LED), a superluminescent diode (SLED), a xenon bulb, or any other suitable type of light source. In one embodiment, the lens 98 is used to focus the light received from a laser source to the linear light 100 and may include one or more cylindrical lenses, or lenses of various other shapes. Lenses are also referred to as "lens systems" because they can include one or more individual lenses or a collection of lenses. Linear light is substantially linear, i.e. the maximum deviation from a straight line is less than about 1% of its length. One lens type that can be utilized by one embodiment is a rod lens. Rod lenses are generally in the form of a glass or plastic full cylinder with a polished peripheral surface and ground ends. Such a lens converts collimation light through the diameter of the rod into a straight line. Another type of lens that can be used can be a cylindrical lens. A cylindrical lens is a lens having the shape of a partially cylindrical body. For example, one surface of a cylindrical lens is flat, while the other surface is cylindrical.

In another embodiment, the projector 94 produces a two-dimensional pattern of light that covers an area of surface 32. At this time, the coordinate acquisition system 78 obtained as a result is called a structured optical scanner.

The second camera 96 includes a sensor 102, such as a charge-coupled device (CCD) type sensor or a complementary metal oxide semiconductor (CMOS) type sensor. The second camera 96 may further include other components, such as, but not limited to, the lens 104 and other optics. The second projector 94 and the second camera 96 are arranged at an angle such that the second camera 96 detects the light 106 from the second projector 94 reflected by the object 34. Since the second projector 94 and the second camera 96 are arranged in a fixed relationship, the above-mentioned trigonometry principle is used to determine the coordinates of a point on the surface 32 on a straight line formed by the light 100. Should be recognized. It should also be recognized that the camera 96 and the projector 94 are provided on both sides of the housing 22 to improve 3D measurement accuracy.

In another embodiment, the second coordinate acquisition system is a sweep linear light, a sweep point light, a coded light pattern (covering an area), or a continuous light (covering an area) as well as a fixed linear light. It is configured to project various patterns that may include light patterns. Each type of projection pattern has different advantages such as speed, accuracy, and exemption from multipath interference. By assessing the performance requirements for each particular measurement and / or examining the characteristics of the recovered data and the expected object shape (from a CAD model or from a 3D reconstruction based on the collected scan data). Allows you to select the type of projection pattern that optimizes performance.

In another embodiment, the distance from the second coordinate acquisition system 78 to the object surface 32 is different from the distance from the first coordinate acquisition system 76 to the object surface 32. For example, camera 96 may be closer to object 32 than camera 88. In this way, the resolution and accuracy of the second coordinate acquisition system 78 can be improved over that of the first coordinate acquisition system 76. In many cases, it is beneficial to quickly scan a relatively large, smooth object with the low resolution system 76 and then scan the details, including edges and holes, with the high resolution system 78.

The scanner 20 can be used in manual mode or automated mode. In manual mode, the operator is prompted to move the scanner closer or farther from the surface of the object according to the acquisition system used. Further, the scanner 20 may project a beam or pattern of light that directs the operator in the direction in which the scanner 20 is moved. Alternatively, the indicator light on the device may indicate the direction in which the scanner should be moved. In automatic mode, the scanner 20 or object 34 can be automatically moved relative to each other according to the measurement requirements.

Similar to the embodiment of FIG. 1, the first coordinate acquisition system 76 and the second coordinate acquisition system 78 are electrically coupled to the control device 50 mounted on the housing 22. The control device 50 may include one or more microprocessors, a digital signal processor, a memory, and a signal conditioning circuit. The scanner 20 may further include an actuator (not shown) that is manually activated by the operator to initiate operation and data acquisition by the scanner 20. In one embodiment, the control device 50 performs image processing for determining the X, Y, Z coordinate data of the point cloud representing the surface 32 of the object 34. The coordinate data can be stored locally, for example in a volatile or non-volatile memory 54. Memory can be removable, for example a flash drive or memory card. In another embodiment, the scanner 20 has a communication circuit 52 that causes the scanner 20 to transmit coordinate data to the remote processing system 56. The communication medium 58 between the scanner 20 and the remote processing system 56 may be wired (Ethernet®, etc.) or wireless (Bluetooth, IEEE 802.11, etc.). In one embodiment, the remote processing system 56 determines the coordinate data, and the scanner 20 transmits the acquired image on the communication medium 58.

Now, with reference to FIG. 4, a method 1400 for operating the scanner 20 of FIG. 3 will be described. At block 1402, the first projector 80 of the first coordinate acquisition system 76 of the scanner 20 radiates a structured light pattern into the area 90 of the surface 32 of the object 34. The light 84 from the projector 80 is reflected from the surface 32, and the reflected light 85 is received by the first camera 82. As mentioned above, changes in the surface profile of surface 32 distort the image-forming pattern of light received by the first photosensitive array 88. In some examples, the controller 50 or remote processing system 56 is between a point on the surface 32 and a pixel in the photosensitive array 88, because the pattern is formed by structured light, straight or light, or pointed light. It is possible to judge the one-to-one correspondence of. In this way, the above trigonometry principle can be used in block 1404 to acquire point cloud data, so to speak, to determine the X, Y, Z coordinates of a point on the surface 32. By moving the scanner 20 relative to the surface 32, a point cloud can be created from the entire object 34.

At block 1406, controller 50 or remote processing system 56 determines if the point cloud data has the desired data quality attributes or has potential problems. The types of problems that can occur are described above with reference to Figure 2, and this description is not repeated here. If the controller determines at block 1406 that the point cloud has the desired data quality attributes, the procedure ends. Otherwise, block 1408 determines whether the scanner is used in manual or automatic mode. When the mode is manual, the operator is guided by block 1410 to move the scanner to the desired position.

As described above with reference to FIG. 2, there are several methods for instructing the desired movement by the operator. The description is not repeated here.

A method of determining the approximate position of the scanner is needed to guide the operator in making the desired movement. As described with reference to FIG. 2, the method involves mounting the scanner 20 on an articulated arm CMM, using an inertial sensor within the scanner 20, illuminating photographic measurement dots, or matching features to a display image. Can include.

After the operator moves the scanner into place, the block 1412 is measured by the second coordinate acquisition system 78. By using the second coordinate acquisition system, the resolution or accuracy is improved or the problem is solved. In block 1414, the procedure ends in block 1416 if all points have been collected. Otherwise continue.

If the mode of operation from block 1408 is automated, at block 1418 the automation mechanism moves the scanner to the desired position. In most cases, the automation mechanism causes the sensor to provide information about the relative position of the scanner and the object to be inspected. In the case where the automation mechanism is a robot, the angle transducer in the robot joint provides information about the position and orientation of the robotic end effector used to hold the scanner. For other types of automation mechanisms, a linear encoder or various other sensors may provide information about the relative position of the object and the scanner.

After the automatic mechanism moves the scanner or object into place, block 1420 makes a three-dimensional measurement by the second coordinate acquisition system 78. Such measurements are repeated by block 1422 until all measurements are complete. The procedure ends at block 1424.

Although the process of FIG. 4 is shown as a linear or sequential process, it should be recognized that in other embodiments, one or more of the indicated steps can be performed in parallel. In the method shown in FIG. 4, the method involves first measuring the entire object and then performing a more detailed measurement according to the evaluation of the acquired point cloud data. The use of the alternative scanner 20 begins by measuring the detailed or critical region using the second coordinate acquisition system 78.

It should also be recognized that providing a method of changing a camera lens or projector lens as a method of changing the FOV of a camera or projector in an existing scanning system is a common practice in existing scanning systems. However, such changes are time consuming and generally involve an additional compensation step in which an artifact such as a dot plate is placed in front of the camera or projector to determine aberration correction parameters for the camera or projector system. I need. Therefore, a system with two different coordinate acquisition systems, such as the scanning system 20 in FIG. 3, has significant advantages in scanner measurement speed and feasibility for fully automated mode.

Errors can occur when making scanner measurements as a result of multipath interference. The sources of multi-path interference will be discussed in the future and the first method for avoiding or reducing multi-path interference will be explained.

Cases of multipath interference occur when some of the light that collides with the surface of an object is first scattered on another surface of the object before returning to the camera. Regarding the points on the object that receive this scattered light, the light sent to the photosensitive array corresponds not only to the light directly projected from the projector but also to the light sent to different points on the projector and scattered by the object. .. Especially in the case of scanners that project two-dimensional (structured) light, the result of multipath interference can be to make the calculated distance from the projector to the surface of the object at this point inaccurate.

An example of multi-path interference is illustrated with reference to FIG. 5A. In this embodiment, the scanner 4570 projects linear light 4525 onto the surface 4510A of an object. The linear light 4525 is perpendicular to the plane of the paper. In one embodiment, the rows of the photosensitive array are parallel to the plane of the paper and the columns are perpendicular to the plane of the paper. Each row represents a point on the projection line 4525 in a direction perpendicular to the plane of the paper. The distance from the projector to the object at this point on the straight line is determined by first calculating the center of gravity of each row. For surface point 4526, the center of gravity on the photosensitive array 4541 is represented by point 4546. The position of the center of gravity 4546 on the photosensitive array can be used to calculate the distance from the camera projection center 4544 to the object point 4526. This calculation is based on the trigonometric relationship based on the principle of trigonometry. To perform these calculations, a baseline distance D from the camera projection center 4544 to the projector projection center 4523 is required. In addition, knowledge of the relative orientation from the projector system 4520 to the camera system 4540 is required.

To understand the errors caused by multipath interference, consider point 4527. Light reflected or scattered from this point is imaged by the lens 4542 at point 4548 on the photosensitive array 4541. However, in addition to the light received directly from the projector and scattered at point 4527, additional light is reflected from point 4526 to point 4527 before being imaged on the photosensitive array. It is very likely that the light will be scattered to unexpected locations, forming two centers of gravity in a given row. As a result, the observation of the two centers of gravity in a given row is a good indication of the presence of multipath interference.

In the case of structured light projected onto an area of the surface of an object, secondary reflections from points such as 4527 are usually not as obvious as light projected onto a straight line, thus causing errors in the measured 3D surface coordinates. Cheap.

By using a projector with an adjustable illumination pattern for the display element 4521, it is possible to change the illumination pattern. The display element 4521 can be a digital micromechanical mirror (DMM) such as a digital optical projector (DLP). Such devices include a number of small mirrors that can be quickly adjusted by electrical signals and quickly adjust the irradiation pattern. Other devices capable of generating electrically adjustable display patterns include LCD (Liquid Crystal Display) and LCOS (Liquid Crystal on Silicon) displays.

A technique for inspecting multipath interference in a system that projects structured light over an area is to modify the display to project linear light. The presence of multiple centers of gravity in the row would indicate the existence of multipath interference. By sweeping the linear light, the area can be covered without the need for operator movement of the probe.

The electrically adjustable display allows the linear light to be set at the desired angle. By changing the direction of the projected linear light, multipath interference can be eliminated in many cases.

For many creases and steeply angled surfaces where reflection is difficult to avoid, an electrically adjustable display is used to sweep the pointed light. In some cases, secondary reflections can occur from a single point of light, but it is usually relatively easy to determine which of the reflected spots of light is effective.

Electroregulatory displays can also be used to quickly switch between coded and uncoded patterns. In most cases, coding patterns are used to make 3D measurements based on a single camera frame information. On the other hand, a large number of patterns (sequential or uncoded patterns) can be used to obtain high accuracy in the measured 3D coordinate values.

In the past, electrically adjustable displays have been used to project each of a series of patterns into a sequential pattern, for example, a series of grayscale linear patterns followed by a continuous sinusoidal pattern, each with a different phase. It is used.

This progressive method prefers a single-shot pattern (eg, a coding pattern) or a multi-shot pattern to identify or eliminate problems such as multipath interference and to obtain the required accuracy as quickly as possible. It offers advantages over previous methods in choosing these methods of deciding whether or not.

In the case of line scanners, there are often methods for determining the presence of multipath interference. In the absence of multipath interference, the light reflected by a point on the surface of the object is imaged as a single row over a region of continuous pixels. Multipath interference is indicated when two or more regions of the row receive large amounts of light. An example of such a multi-path interference condition and the resulting extra irradiation area of the photosensitive array are shown in FIG. 5A. Surface 4510A now has a large curvature near intersection 4526. The vertical surface at the intersection is a straight line 4528 and the angle of incidence is 4531. The direction of the reflected linear light 4529 is determined by the reflection angle 4532, which is equal to the incident angle. As mentioned above, the linear light 4529 actually represents the entire direction of light scattered over an angular range. The center of the scattered light collides with the surface 4510A at point 4527, which is imaged by lens 4544 at point 4548 on the photosensitive array. An unexpectedly large amount of light received near point 4548 indicates that multipath interference is probably present. In line scanners, the main concern about multipath interference is not the case shown in Figure 5A where the two spots 4546 and 4527 are separated by a considerable distance and analyzed separately, but rather the two spots overlap. This is an example of bleeding together. In this case, it is not possible in FIG. 15E to determine the center of gravity corresponding to the desired point corresponding to point 4546. The problem is exacerbated in the case of a scanner that projects light over a two-dimensional area, as can also be understood by referring to Figure 5A. If all of the light imaged on the photosensitive array 4541 is needed to determine the two-dimensional coordinates, then the light at point 4527, along with the desired pattern of light projected directly from the projector, is a point from the surface of the object. It is clear that it also corresponds to the unwanted light reflected to 4527. As a result, in this case, the wrong 3D coordinates could be calculated at point 4527 for the light projected over the entire area.

For the projected linear light, in many cases it is possible to eliminate multi-path interference by changing the direction of the straight line. One possibility is to build a line scanner using a projector with unique two-dimensional performance so that the line is swept or automatically rotated in different directions. An example of such a projector is one that uses a digital micromirror (DMD) as described above. For example, if multipath interference is suspected in a particular scan captured by structured light, the measurement system may be automatically configured to switch to a measurement method that uses linear light from sweeps.

Another way to mitigate, minimize, or eliminate multi-path interference is to sweep punctate light rather than linear or optical areas over the area where multi-path interference is noted. By irradiating a single point of light, the light scattered by the secondary reflection can usually be easily identified.

The determination of the desired pattern projected by the electrically adjustable display is made using diagnostic analysis, as described below with reference to FIG.

In addition to its use in diagnosing and correcting multipath interference, changing the pattern of projected light has the advantage of obtaining the required accuracy and resolution in the least amount of time. In one embodiment, the measurement is first performed by projecting a coded pattern of light onto an object in a single shot. The three-dimensional coordinates of the surface are determined using the collected data and the results are analyzed to determine if some regions have holes, edges, or features that require more detailed analysis. Such detailed analysis can be performed, for example, by using the narrow angle FOV camera 24 of FIG. 1 and the high resolution scanner system 78 of FIG.

The coordinates are analyzed to determine the approximate distance to the target, and thus for more accurate measurement methods, such as the method of continuously projecting a sinusoidal phase-shifted light pattern onto the surface, as described below. Provide a starting distance. Finding the starting distance for each point on the surface using a coded light pattern eliminates the need to obtain this information by varying the pitch in a number of sinusoidal phase shift scans, thus saving considerable time.

Now, referring to FIG. 5B, an embodiment for overcoming the abnormality of the coordinate data acquired by the scanner 20 or improving the accuracy is shown. By scanning an object, such as object 34, with scanner 20, process 211 begins at block 212. The scanner 20 can be, for example, a scanner as described in the embodiments of FIGS. 1, 3, 5 and 7, having at least one projector and a camera. In this embodiment, at block 212, scanner 20 projects a first light pattern onto an object. In one embodiment, this first light pattern is a coded and structured light pattern. Process 211 acquires and determines 3D coordinate data in block 214. The coordinate data is analyzed in question block 216 to determine if there are any anomalies such as the multipath interference described above, low resolution around the element, or the absence of data due to changes in surface angle or surface reflectance. If an anomaly is detected, process 211 proceeds to block 218, where the light pattern emitted by the projector is changed to the second light pattern. In one embodiment, the second light pattern is linear light from sweeping.

After projecting the second light pattern, process 211 proceeds to block 220, where three-dimensional coordinate data is acquired and determined for the area where the anomaly is detected. Process 211 loops back to question block 216, where it is determined if the anomaly has been resolved. If question block 216 still detects anomalies or omissions, accuracy or resolution, the process loops back to block 218 and switches to the third light pattern. In one embodiment, the third light pattern is a continuous sinusoidal phase shift pattern. In another embodiment, the third light pattern is swept point light. This iterative procedure continues until the anomaly is resolved. Once the coordinate data from the anomalous area is determined, process 211 proceeds to block 222, where the radiation pattern switches back to the first structured light pattern and the scanning process continues. Process 211 continues until the operator scans the desired area of the object. In the event of insufficient scanning of the information obtained using the method of Figure 11, the problem of measurement with the tactile probe described here can be used.

Now, with reference to FIG. 6, another embodiment of the scanner 20 is shown attached to the mobile device 120. Scanner 20 with at least one projector 122 and at least one camera 124 arranged in a certain geometric relationship so that the principle of trigonometry can be used to determine the three-dimensional coordinates of a point on surface 32. Has. The scanner 20 can be, for example, the same scanner as described with reference to FIG. 1 or FIG. In one embodiment, the scanner is the same as the scanner of FIG. 10 having a tactile probe. However, the scanner used in the embodiment of FIG. 6 is a scanner such as a structured optical or line scanner, eg, a portable coordinate measuring machine with an integrated line laser scanner, on January 18, 2006. It may be the scanner filed and disclosed in US Pat. No. 7,246,030 by the same owner. In another embodiment, the scanner used in the embodiment of FIG. 6 is a structured optical scanner that projects light over an area of an object.

In an exemplary embodiment, the movable device 120 is a robotic device that provides automatic movement by arm segments 126,128 connected by a swivel swivel joint 130 to move the arm segments 126,128, resulting in a scanner 20 (FIG. 6). Move from the 1st position to the 2nd position (as marked by the dotted line). The movable device 120 may include an actuator such as a motor (not shown) that is coupled to the arm segments 126,128 and moves the arm segments 126,128 from the first position to the second position. It should be recognized that the mobile device 120 with the articulated arm is for illustrative purposes only and the claimed invention should not be so restricted. In other embodiments, the scanner 20 may be attached to a mobile device that moves the scanner 20, for example via rails, wheels, tracks, belts, cables, or a combination of the above. In other embodiments, the robot has a different number of arm segments.

In one embodiment, the mobile device is an articulated arm coordinate measuring machine (AACMM), as described in US Patent Application No. 13 / 491,176 by the same holder, filed January 20, 2010. Is. In this embodiment, the movement of the scanner 20 from the first position to the second position requires the operator to manually move the arm segments 126,128.

For embodiments with an automation device, the mobile device 120 further includes a control device 132 configured to energize the actuator to move the arm segments 126,128. In one embodiment, the control device 132 communicates with the control device 134. As detailed below, this arrangement allows the scanner 20 to be moved by the controller 132 in response to anomalies in the acquired data. It should be recognized that the controllers 132, 134 can be integrated into a single processing unit or the functions can be distributed within several processing units.

By performing the analysis with reference to FIG. 12, it is possible to determine the position and orientation of the scanner 20 and obtain the desired measurement results. In some embodiments, the feature being measured may utilize a scanner in the desired orientation. For example, the measurement of hole diameter can be improved by orienting the scanner camera 124 so that it is approximately perpendicular to the hole. In other embodiments, the scanner may be positioned to reduce or minimize the likelihood of multipath interference. Such an analysis may be based on a CAD model available as part of the diagnostic procedure or based on the data collected by the scanner in the initial position prior to the secondary movement of the scanner 20 by device 120.

Now, with reference to FIG. 7, the operation of the scanner 20 and the movable device 120 will be described. The process begins at block 134, which scans object 34 with scanner 20 in position 1. At block 138, the scanner 20 acquires and determines coordinate data about a point on the surface 32 of the object 34. The mobile device 120 can move the scanner 20 to obtain data about surface points in a desired area. Question block 140 determines if there is an anomaly in the coordinate data at point 142, for example multi-path interference, or if there is a need to change direction to improve resolution or measurement accuracy. Point 142 in FIG. 6 can represent a single point, point line, or area on surface 32. If an anomaly or need for accuracy improvement is detected, the process continues to block 144, where the mobile device 120 moves the position of the scanner 20, such as from position 1 to position 2, and blocks 146 the area of interest. Rescan to acquire 3D coordinate data. The process loops back to question block 140, where it is determined if the coordinate data is still anomalous or if improved measurement accuracy is desirable. In these cases, the scanner 20 is moved again and the process continues until the measurement results reach the desired level. Once the coordinate data is obtained, the process proceeds from question block 140 to block 148, where the scanning process continues until the desired area is scanned.

In embodiments where the scanner 20 includes a tactile probe (FIG. 10), the movement of the scanner from position 1 to position 2 may be configured to bring the area of interest into contact with the tactile probe. Since the position of the scanner, and thus the tactile probe, can be determined from the position and orientation of the arm segments 126,128, the three-dimensional coordinates of the points on the surface 32 can be determined.

In some embodiments, the measurement results obtained by the scanner 20 in FIGS. 8A, 8B can be disturbed by multipath interference. In other cases, the measurement results do not provide the desired resolution or accuracy to accurately measure the properties of the surface 32, especially edges, holes, or complex features. In these cases, it is desirable for the operator to use the remote probe 152 to query a point or area on the surface 32. In one embodiment shown in FIGS. 8A, 8B, the scanner 20 has a projector 156 and a projector 156 such that the light emitted by the projector 156 is reflected by the surface 32 and received by one or both of the cameras 154, 155. Includes cameras 154,155 and are arranged at an angle to. The projector 156 and the cameras 154, 156 are arranged in a certain geometric relationship so that the principle of trigonometry can be used to determine the three-dimensional coordinates of a point on the surface 32.

In one embodiment, the projector 156 is configured to emit visible light 157 to an area of interest 159 on the surface 32 of the object 34, as shown in FIG. 8A. The three-dimensional coordinates of the illuminated area of interest 159 can be confirmed by using the image of the illuminated area 159 with one or both of the cameras 154,155.

The scanner 20 is configured to work with the remote probe 152 so that the operator can bring the probe tip 166 into contact with the object surface 132 in the illuminated region of interest 159. In one embodiment, the remote probe 152 comprises at least three non-collinear punctate lights 168. The pointed light 168 is a spot of light generated by a light emitting diode (LED) or a reflective bright spot of light emitted by an infrared or visible light source from a projector 156 or another light source not depicted in FIG. 8B. Can be. The infrared or visible light source of this case can be mounted on the scanner 20 or provided outside the scanner 20. By determining the three-dimensional coordinates of the spotted light 168 with a scanner, and by using the information about the geometry of the probe 152, the position of the probe tip 166 is determined, thus the coordinates of the object surface 32. Can be done. Tactile probes used in this way eliminate the potential problems of multipath interference and also allow for relatively accurate measurements of holes, edges, and detailed features. In one embodiment, the probe 166 can be a tactile probe that can be activated by pressing an actuator button (not shown) of the probe, or the probe 166 can be a touch trigger probe that can be activated by contact with the surface 32. A communication circuit (not shown) transmits a signal to the scanner 20 in response to a signal generated by the actuator button or touch trigger probe. In one embodiment, the pointed light 168 is replaced with a geometric light pattern, which may include straight lines or curves.

Now, with reference to FIG. 9, the process for using the stationary scanner 20 of FIGS. 8A, 8B together with the remote probe 152 to obtain coordinate data about a point on the surface 32 of the object 34 is shown. The process begins at block 170 and the surface 32 of object 34 is scanned. The process acquires and determines the 3D coordinate data of surface 32 at block 172. The process then determines in question block 174 if there is an anomaly in the coordinate data in area 159, or if there is a problem with the accuracy or resolution of area 159. The anomaly can be invalid data that is discarded, for example due to multi-path interference. Anomalies can be missing data due to lack of surface reflectance or resolution around features such as openings and holes. Diagnostic procedures for detecting (identifying) multipath interference and related problems are given with reference to FIG.

Once the area 159 has been identified, the scanner 20 instructs the operator at block 176 that the coordinate data for the area 159 can be acquired via the remote probe 152. This area 159 can be indicated by emitting visible light 157 to irradiate the area 159. In one embodiment, the light 157 is emitted by the projector 156. The color of light 157 can be changed to inform the operator of the type of anomaly or problem. For example, where multi-path interference occurs, light 157 can be red, whereas low resolution can be green. Areas can also be indicated on a display that has a graphic representation of the object (such as a CAD model).

The process then proceeds to block 178, where when sensor 166 touches surface 32, it acquires an image of remote probe 152. Pointed light 168, which can be an LED or reflective target, can be received, for example, by one of the cameras 154,155. Using the best fit technique well known to mathematicians, the scanner 20 determines in block 180 the three-dimensional coordinates of the probe center where the three-dimensional coordinates of the object surface 32 are determined in block 180. Once a point in area 159 where the anomaly has been detected is acquired, the process proceeds to continue scanning object 34 at block 182 until the desired area is scanned.

Now, with reference to FIG. 10, another embodiment of the scanner 20 gripped by the operator during operation is shown. In this embodiment, the housing 22 may include a handle 186 that allows the operator to hold the scanner 20 during operation. The housing 22 includes a projector 188 and a camera 190 arranged at an angle to each other so that the light 192 emitted by the projector is reflected by the surface 32 and received by the camera 190. The scanner 20 of FIG. 10 operates in a manner substantially similar to the embodiments of FIGS. 1 and 3 and uses the principle of trigonometry to acquire three-dimensional coordinate data of points on the surface 32.

The scanner 20 further includes an integrated probe member 184. The probe member 184 includes a sensor 194 at one end. The sensor 194 may be a tactile probe capable of responding to a press of an actuator button (not shown) by an operator, or, for example, a touch trigger probe responding to contact with a surface 32. As will be described in more detail later, the probe member 184 allows the operator to obtain the coordinates of a point on the surface 32 by bringing the sensor 194 into contact with the surface 32.

The projector 188, the camera 190, and the actuator circuit for the sensor 194 are electrically coupled to the control device 50 mounted in the housing 22. The control device 50 may include one or more microprocessors, a digital signal processor, a memory, and a signal conditioning circuit. The scanner 20 may further include, for example, an actuator (not shown) such as on a handle 186 that can be manually activated by the operator to initiate operation and data acquisition by the scanner 20. In one embodiment, the control device 50 performs image processing for determining the X, Y, Z coordinate data of the point cloud representing the surface 32 of the object 34. The coordinate data can be stored locally, for example in a volatile or non-volatile memory 54. Memory, for example a flash drive or memory card, can be removable. In another embodiment, the scanner 20 has a communication circuit 52 for the scanner 20 to transmit coordinate data to the remote processing system 56. The communication medium 58 between the scanner 20 and the remote processing system 56 is wired (such as Ethernet®) or wireless (Bluetooth, IEEE). 802.11, etc.). In one embodiment, the coordinate data is determined by the remote processing system 56, and the scanner 20 transmits the acquired image on the communication medium 58.

Now, with reference to FIG. 11, the operation of the scanner 20 of FIG. 10 will be described. The process begins at block 196, where the operator scans the surface 32 of object 34 by manually moving the scanner 20. At block 198, 3D coordinates are determined and acquired. In the question block 200, it is determined whether or not there is an abnormality in the coordinate data or whether or not accuracy improvement is required. As mentioned above, anomalies can occur for several reasons, such as multipath interference, surface reflectance changes, or low resolution of features. If anomalies are present, the process proceeds to block 202, where area 204 is directed to the operator. Area 204 can be indicated by projecting visible light 192 onto surface 32 with projector 188. In one embodiment, the light 192 is colored to notify the operator of the type of anomaly detected.

The operator then moves the scanner from the first position to the second position (indicated by the dotted line) at block 206. In the second position, the sensor 194 comes into contact with the surface 32. The position and orientation (6 degrees of freedom) of the scanner 20 in the second position can be determined using a well-known best fit method based on the image acquired by the camera 190. Since the dimensions and arrangement of the sensor 194 are well known with respect to the mechanical structure of the scanner 20, the 3D coordinate data of the points in area 204 can be determined in block 208. The process then proceeds to block 210, where scanning of the object continues. The scanning process continues until the desired area has been scanned.

A general approach can be used to evaluate overall quality, including the effects of resolution and material type, surface properties, and geometry, as well as multipath interference. Also with reference to FIG. 12, in one embodiment, method 4600 may be performed automatically under computer control. Step 4602 determines if information about the three-dimensional coordinates of the object to be inspected is available. The first type of 3D information is CAD data. CAD data usually refers to the nominal dimensions of the object to be inspected. The second type of three-dimensional information is measured three-dimensional data, such as previously measured data by a scanner or other device. In some cases, step 4602 may include a further step of aligning the reference frame of a coordinate measuring device, such as a laser tracker or 6DOF scanner accessory, with the reference frame of the object. In the position embodiment and subsequent embodiments, this is done by measuring at least three points on the surface of the object with a laser tracker.

If the answer to the question presented in step 4602 is that 3D information is available, then in step 4604 the computer or processor can calculate the impact of the object measurement on multipath interference. used. In one embodiment, this is done by projecting each ray emitted by a scanner projector and calculating the angle or reflectance for each case. The computer or software identifies each area of the object surface that is susceptible to errors as a result of multipath interference. Step 4604 can also perform an analysis of the susceptibility to multipathic errors for various positions of the 6DOF probe with respect to the object to be inspected. In some cases, as mentioned above, multipath interference can be avoided or minimized by choosing the appropriate position and orientation of the 6DOF probe with respect to the object to be inspected. If the answer to the question presented in step 4602 is that 3D information is not available, then step 4606 is to measure the 3D coordinates of the object surface using a desired or suitable measurement method. is there. Following the calculation of multipath interference, step 4608 may be performed to evaluate other aspects of the expected scan quality. One such quality factor is whether the scan resolution is sufficient for the characteristics of the object to be inspected. For example, if the resolution of the device is 3 mm and there are features where the effective scan data is less than the desired millimeter, the problem areas of these objects should be noted for later correction operations. Another quality factor that is partly related to resolution is the ability to measure the edges of objects and the edges of holes. Knowledge of scanner performance makes it possible to determine if the scanner resolution is good enough for a given edge. Another quality factor is the amount of light expected to return from a given feature. It is expected that a small amount of light will return to the scanner from inside the small hole, for example from the viewing angle. Also, a small amount of light is expected from certain and colored materials. Some materials are light from a scanner Has a large penetration depth, and good measurement results are not expected in this case. In some cases, the automated program asks for additional user information. For example, if a computer program is performing steps 4604,4608 based on CAD data, the type of material known for the surface properties of the object to be inspected is not used. In these cases, step 4608 may include another step of acquiring material properties for the object to be inspected.

Following the analysis of steps 4604,4608, step 4610 is to determine if further diagnostic procedures should be performed. The first example of a possible diagnostic procedure is step 4612, which projects the stripes at a suitable angle to note whether multipath interference is observed. Schematic instructions for multipath interference for the projected straight stripes are given above with reference to FIG. Another example of the diagnostic step is step 4614, which projects a collection of straight lines aligned in the direction of the epipolar straight line in the source pattern of light, eg, the source pattern of light 30 from projector 36 in FIG. For cases where linear light in the light source pattern is aligned with epipolar straight lines, these straight lines appear as straight lines in the image plane on the photosensitive array. The use of Epipolar Line is further detailed in US Patent Application No. 13 / 443,946 by the same owner filed April 11, 2012. If these patterns in the photosensitive array are not straight lines, or if the lines are blurry or noisy, problems are pointed out, probably as a result of multipath interference.

Step 4616 is to select a suitable combination of actions based on the analytical and diagnostic procedures performed. Step 4618 is preferred when measuring using a 2D (structured) pattern of coded light when measurement speed is particularly important. When high accuracy is more important, step 4620 is preferred to measure a 2D (structured) pattern of encoded light using a continuous pattern, eg, a continuous sinusoidal pattern with different phases and pitches. If method 4618 or 4620 is selected, reposition the scanner, in other words, adjust the position and orientation of the scanner to a position that minimizes the multipath interference and specular reflection &lt;glint&gt; obtained by the analysis in step 4604. It is also desirable to select step 4628. Such instructions may be provided to the user by illuminating the problem area with light from a scanner projector or by displaying such an area on a monitor display. Alternatively, the next step in the measurement procedure may be automatically selected by the computer or processor. If a suitable scanner position does not eliminate multipath interference and glint, several options are available. In some cases, the scanner can be rearranged and valid measurement results combined to repeat the measurement. In other cases, alternative measurement steps are added to the procedure or performed instead of using structured light. As mentioned above, step 4622, which scans the stripes of light, provides a convenient way to obtain information for the entire area, reducing the risk of having problems due to multipath interference. Step 4624, which sweeps a small spot of light over the region of interest, reduces the risk of problems due to multipath interference. The step of measuring an area on the surface of an object with a tactile probe eliminates the possibility of multipath interference. Tactile probes provide well-known resolution based on the size of the probe tip, eliminating the problem of low reflectance light or large light transmission depth found in objects under inspection.

In most cases, the quality of the data collected in the combination of steps 4618-4628 can be evaluated in step 4630 based on the data obtained from the measurements and combined with the results of the previously performed analysis. If the quality is found to be acceptable in step 4632, the measurement is completed in step 4634. Otherwise, analysis resumes at step 4604. In some cases, the 3D information was not as accurate as desired. In this case, it is beneficial to repeat some of the previous steps.

Although the invention has been described in detail with respect to only a limited number of embodiments, it should be readily understood that the invention is not limited to such disclosed embodiments. Rather, the invention may be modified to include some modifications, modifications, alternatives, or equivalent configurations that are not described above but are compatible with the gist and scope of the invention. In addition, although various embodiments of the invention have been described, it should be understood that aspects of the invention include only some of the described embodiments. Therefore, the present invention is not considered to be limited by the above description, but is limited only by the appended claims.