Opto-electronic sensor

The invention relates to an opto-electronic sensor having a light transmitter for the transmission of light signals in a Monitoring area and a light receiver for receiving of the emitted light signals from the light transmitter, wherein a directly or indirectly, by the light receiver acted upon evaluation for generating an object detection signal in the case of the presence of an object in the surveillance area is provided.

Such sensors are, for example, as a simple light barriers or multi-beam light grid systems for access control used, in particular dangerous Machine working zones or specific spaces within a building should be secured.

If the case of sensors of the type mentioned an object in the monitored zone passes and thus the optical path between Light emitter and light receiver interrupts, an object detection signal generated, which, for example, the shutdown of the machine or to trigger an can cause audible or visual warning process.

In known systems, the decision is based on whether the light path is interrupted between the transmitter and receiver or not, as a rule, on a purely energetic viewing, which means that whenever the received Quantity of light falls below a certain value, the Interruption of the light path and thus on the presence an object is closed in the monitoring area.

A problem with known systems is the fact that in certain applications, reflective objects within the transmission angle of the light transmitter or within the may be arranged visual range of the light receiver, which are generally permitted, so no object detection signal should trigger but may cause that an invalid object in the surveillance area umspiegelt becomes. In such an example, mirroring the central light beam between the light transmitter and Light receiver is interrupted by an illegal object be, but by the specified permissible reflective yet passed objects as much light on the light receiver be that the critical light quantity value does not fall below is and, consequently, the generation of an object detection signal is omitted. In the known sensors can therefore not be guaranteed that all the monitoring area existing illegal objects reliably are detected.

An object of the invention is an optoelectronic educate sensor of the type mentioned, that its reliability is enhanced, in particular the disturbing influence of allowable reflective Objects in the vicinity of the surveillance area or in the monitoring area to be even eliminated.

According to the invention this object is achieved by the fact that the Light receiver as a spatially resolving receiving element for determining the position of the received light gravity in the region formed of the light-sensitive surface of the receiver element is that a cooperating with the evaluation circuit Storage element for storing at least a target position the received light gravity is provided, and that the evaluation means for comparing during determined operation of the sensor actual positions with having a stored desired position with an object detection signal can be generated for the case where the deviation of the actual position from the target position an exceeds defined threshold.

According to the invention is used as light receiver no longer so a used example of the prior art simple Photodiode is used, but it is instead a spatially resolving receiving element used, which has a comprises light-sensitive surface, wherein the spatially resolving is receiving element designed so that the position of Receiving light center of gravity on the photosensitive surface can be determined. For the position of the received light gravity on the photosensitive surface of the receiving element is a nominal position specified which during operation the inventive sensor with the determined actual positions is compared. By introducing an unacceptable Object in the surveillance area, the position of Receiving light center of gravity on the photosensitive surface moved, one object detection signal then is generated when this shift of the operation of the Sensor determined actual position in relation to the nominal position, exceeds a defined threshold.

According to the inventive principle is thus the recognition a present in the monitored area impermissible object also possible when in the vicinity of the surveillance area permissible or surveillance area reflecting objects are arranged such that a substantial Proportion of the radiation emitted by the light transmitter Luminance even when disconnected from the central beam of light through a permitted object is passed to the light receiver, ie if the permissible objects for a mirroring of unauthorized Object lead. The reliability of the present invention Sensor is thus opposite from the prior art known sensors significantly improved.

An advantage of the inventive sensor persists that a more flexible application range is given as Sensors according to the invention is very close to permissible reflective can be installed objects, without any these reflective objects negatively on the reliability the sensor effect.

Another advantage is that in the production of an inventive Sensor not very precise adjustment of the individual optical components is another necessary or that expensive opto-mechanical components are used , since for each sensor produced after completion the production process in each case a setpoint determined is then automatically all problems encountered in the production wearing inaccuracies bill. Reference is illustrative noted that occurring in the production inaccuracies only result in the desired position of the received light gravity on the photosensitive surface with respect to an ideal mounted sensor is shifted which but has no adverse effects, since simply the shifted reference position than actual target position can be stored, which is then - as already mentioned - automatically transmits all inaccuracies bill.

It is preferred if the spatially resolving receiver element from a line array of a plurality of photosensitive Elements. However, it is also possible to provide several provide photosensitive elements in a matrix arrangement, said matrix then the photosensitive area of ​​the entire Receiving element forms. When using a linear array, that is, a one-dimensional-receiving element, can which are detected and eliminated those Umspiegelungen, which occur within a plane which is at least in the substantially parallel to the row arrangement of the Receiving element forming photosensitive elements extends. When using an array, however, can which are detected and eliminated any Umspiegelungen, that occur in any plane which is parallel runs to the optical axis of the overall sensor system.

When using an array of individual photosensitive Elements, offers the use of CCDs.

The individual light-sensitive elements of a row or Matrix array, for example, as a photodiode or than others, for the detection of light signals suitable elements be formed.

Particularly however, it is also possible in the present invention provided spatially resolving receiver element as a single or two-dimensional PSD, ie as a position-sensitive detector form. A position sensitive detector is an electro-optical Element having a photosensitive surface, wherein the detector provides for example two streams of the amplitude ratio to the related to a dimension Position of a light spot on the light sensitive area the PSD will be closed. If a four streams donating PSD is employed, from the amplitude ratio these currents to one another on the two dimensions based on Position of a light spot on the light-sensitive Surface of the PSD are closed.

It is particularly advantageous if a desired position of the Received light gravity by means of a teach-in procedure is identifiable and stored. In this case, the Inventive sensor individually to the respective Of use given conditions are adapted. When performing the teach-in procedure at the site is the position the received light spot may already existing, permitted, reflecting objects affected. Thus, when the target to be stored position under the teach-in process is determined such that a light signal in the free of illegal objects monitoring area is transmitted and received again, sets the position of caused by this light signal light spot on of the light-sensitive surface of the individual Circumstances coordinated setpoint value. The End User the sensor according to the invention is thus by means of the said Teach-in method capable of, an individual make adjustment to the particular conditions of use, without these conditions already in the manufacturing process the sensor must be considered. this makes possible diverse uses of the present invention trained sensor.

The spatially resolving receiver element of the sensor can range placed the focus of an imaging optical receiving system , whereby here chiefly because of said teach-in procedure given the ability to learn Sensor is not exactly on the observance of the exact position the receiving element must be taken at the focal point. It is quite conceivable that the spatially resolving receiver element with respect to the imaging optical receiving system also intra- or extrafocally is arranged.

Light emitter and light receiver can on opposite Sides of the monitored zone are arranged. Alternatively, it is possible, the light transmitter and light receiver on the same side of the monitored region and a retroreflector on the opposite side of the monitored zone provide. The latter variant corresponds to a Auto-collimation.

The sensor of the invention can also in a light grid arrangement be used, in which case each have a Majority disposed of adjacent light transmitters and arranged light receivers in the structure required in each case will.

the light receiver of the light grid arrangement Preference designed as a one-dimensional receiver elements. This one-dimensional Receiving elements arranged twisted to one another be, the axis of rotation that corresponds to the axis, which mutually associated light transmitter and light receiver together. It is advantageous, when the twist angle between adjacent receiving elements is 90 °. In this way, an inventive Light grid arrangement capable of, any Umspiegelungen to detect and eliminate the arbitrary in a Level by which Verdrehachsen said parallel to the runs. Thus, although only one-dimensional Receiving elements are used, due to the eliminated described twist any Umspiegelungen will.

In a method for operating a sensor according to the invention one or more to be stored desired positions - Are determined by the sensor - as already mentioned on site under conditions of use in an object-free Monitoring area is operated. The monitoring area However, this may very well be permissible reflecting objects have, it may in determining the desired position only no illegal objects exist. If possible at a work different conditions of use are, for each of these conditions, a target value are determined and stored, in which case the different desired positions, for example by may be a selector switch activated. Alternatively, it is also possible, all stored desired positions simultaneously activate, so that only an object detection signal is issued when the actual position of all determined nominal positions in a respective predetermined Degree differs.

The actual and desired positions in the form of a Dimension representing values ​​or in the form of two dimensions identified and processed representing coordinate values will.

providing when using an at least two partial flows Receiving element (PSD), wherein the partial streams the position the received light gravity feature, can be used as the determined Position quantity characterizing the quotient processed a partial flow and the total flow of the partial streams will. In this way permissible reflections be very well distinguished from illegal reflections, what in conventional PSD calculation algorithms where in Typically, the quotient between the difference between the two partial flows and the sum current is formed, not the case is.

Furthermore it is advantageous if, for in a method Operation of a system according to the invention with a plurality of light transmitters and light receivers in light grid arrangement a uniform shift of the received light focus all light receiver as permissible Systemdejustage or permissible low frequency vibration is classified, so that in these cases not express an object detection signal takes place. In this way, a higher System availability, ie a lower susceptibility to interference the system guarantees.

It is preferred if the presence of the spatially resolving Receiving element is used in addition to inevitable to compensate for opto-mechanical system tolerances in light grids. Such system tolerances are, for example due by the torsion of used for light curtain Mounting profiles, by wedge errors in lenses through decentered layers of screens, etc. To achieve the above compensation effect, is within a calibration the target position for each position-sensitive receiving element determined separately and, for example, together with an associated permissible displacement tolerance deposited. So lets achieved that the inventive light grid system existing accordance with safety standard requirements regarding met the pivoting while a maximum Adjustment range for the end user permits.

Finally, it is in a method for operating a Sensor of the invention advantageous when an object detection signal is always emitted when either the deviation of the determined actual position of the stored target position exceeds the defined threshold or when the received light amount by the light receiver a defined minimum value falls below. At occurrence the extreme case in which the light receiver, for example, absolutely no or only receive very little light, and are consequently not detecting the actual position of the light spot can, it is thus also possible to object detection signal to generate, as in this case, by the light receiver amount of light received a defined minimum value below.

Further preferred embodiments are defined in the subclaims indicated. The invention includes any combination the sub-claims, in particular also of the method claims among themselves.

The invention is described by means of embodiments described with reference to the drawings; in These show:<dl tsize="7"><dt>Fig. 1</dt><dd>a schematic diagram of an inventive sensor assembly without reflecting objects in the monitoring area or in the vicinity of the surveillance area,</dd><dt>FIG. 2</dt><dd>a schematic diagram of an inventive sensor assembly with a permissible reflecting Object in the vicinity of the surveillance area,</dd><dt>Fig. 3</dt><dd>a schematic diagram of an inventive sensor assembly with a permissible reflecting Object in the vicinity of the surveillance area, and an invalid object in the surveillance area, and</dd><dt>Fig. 4</dt><dd>a schematic diagram of an inventive sensor in auto-collimation with a permissi-denominated reflecting object in the vicinity of the surveillance area and another permissible reflective object in the surveillance area.</dd></dl>

Fig. 1 shows an LED configured as light transmitter 1 which a cone of light in the direction of a transmitting optical system 2 emits. The optical axis 3 of the transmitting optical system 2 coincides with the optical axis of an optical receiving system 4 together, their the transmitting optical system 2 opposite side designed as a PSD is light receiver 5 provided.

Between the transmitting optical system 2 and the optical receiving system 4 the monitoring area. 6

The spatially resolving light receiver 5 provides a from the position the incident thereon light spot dependent signal to an evaluation circuit 7, which with a memory element 8 for storing a target position and with a Means 9 for comparing the nominal position with a determined Actual position is equipped.

The transmitting optical system 2 focuses the light from the transmitter 1 emitted Light such that a large part of this light parallel to the 3 optical axis is directed onto the reception optics 4th On Part of the light emitted by the light transmitter 1 light but obliquely radiated to the optical axis 3 and therefore passes not on the receiving optics 4. This situation is made the drawn in FIG. 1 arrows show which the light paths described illustrate.

In the operating position of the sensor shown in Fig. 1 are neither permitted nor prohibited reflective Objects in the surveillance area 6 or near the Monitoring area 6, so that the light emitted by the light transmitter 1 Light unaffected by such objects on the light receiver 5 passes. The generated on the light receiver 5 Light spot is shown in FIG. 1 thus in its zero position, illustrating the reference numeral 10 is. This zero position 10 is preferably located in the Center of the photosensitive surface of the light receiver fifth

The operating state of FIG. 1 is thus capable a nominal position of the imaged on the light receiver 5 to determine the light spot, said target position of the zero position 10 corresponds. This target position can in the storage element 8 of the evaluation circuit 7 is stored, so that it for a later comparison with actual positions available stands.

FIG. 2 shows the arrangement according to FIG. 1, in addition here below the monitoring area 6 a permissible reflecting object 11 is present whose reflective Surface extends parallel to the optical axis 3, and facing the monitoring area. 6

The arrows shown in Fig. 2 illustrate that a Part of the light emitted by the light transmitter 1 light on the reflective surface of the permissible reflecting object 11 impinges and passes from there to the receiving optics. 4 The receiving optics 4 bundles the the permissible reflecting object 11 reflected light such that on the light-sensitive surface of the light receiver 5, a second Light spot at the position marked 12 position arises, which is spaced from the null position 10th

The evaluation circuit 7 is capable of, the center the light intensity of the two at the zero position 10 and the position to calculate 12 contained light spots. In This calculation includes both the positions of the two Light spots as well as in the field of two light spots each received light amounts. It must therefore be a distance X of such averaged center of the light intensity from the zero position 10. The distance X is smaller than the distance of the position 12 of the zero position 10th

The distance X thus indicates a target position of the Sum of the received light spots under the operating conditions according to FIG. 2 with a permissible reflecting object 11 in the vicinity of the monitored zone 6. It is possible, this desired value determined in addition to FIG. 1 save setpoint as an additional setpoint. It is also possible to store only the target value determined in accordance with FIG. 2. For storage of two nominal values ​​the production takes place an object detection signal each time, when the detected value of both setpoints is different.

Fig. 3 shows the arrangement according to FIG. 2, with the difference that now in the monitoring area 6 a permitted object 13 is present, which is optically opaque, preventing, that light from the transmitting optical system 2 parallel to the optical Axis 3 reaches the receiving optics. 4

It still comes as shown in FIG. 3, however, part of the Light source 1 emitted light to the reflecting surface the permitted object 11, from where this light fraction is directed to the receiving optics. 4 According to FIG. 2 pools the receiving optics 4 in this way, the received Light component and therefore causes the formation of a light spot 5 at the position 12 on the light receiver Now, if the Evaluation 7 under the conditions shown in FIG. 3 again the center of the light intensity of the received light spots determined, so this position is of the under Fig.2 differ determined position as shown in FIG. 3 at the zero position 10 due to the existing invalid object 13 no light spot is received. The determined according to FIG. 3 Center of the light intensity is thus in terms of its coinciding position with the position 12 of that the place Light spot describes what the mirroring caused the permissible reflecting object 11 becomes. The center of the light intensity thus has according to 3 shows a distance Z from the zero position 10 which the distance X shown in FIG. 2 is different.

If now in the evaluation circuit 7 in the comparison means 9 stored as shown in FIGS. 1 and 2 target positions . 3 are compared to the actual position of FIG, so can be noted that the deviation Z no setpoint corresponds, so that the presence of an object or an invalid object in the monitoring area 6 closed can be.

Despite the FIG. 3 takes place and by the permissible Object 11 caused mirroring can thus the impermissible object 13 detected reliably. It can not - as in the prior art - done that Mirroring the object 11 causes a sufficient Light amount is received and alone because of this fact the delivery of an object detection signal is omitted.

Fig. 4 shows an opto-electronic sensor according to the invention in auto-collimation. Light transmitter 14 and light receiver 15 are on one side of a monitored zone 6 is arranged, during the on the opposite side Monitoring region 6, a retroreflector 16 is provided Spieqel which two 17, 18 that a deflection of the emitted by the light emitter 14 light beam back to the light receiver 15 cause. can instead of the retroreflector 16 a Tripelspiegelsystem be provided.

In monitoring area 6 is a permissible reflecting Object 19. Above the monitoring region 6 arranged another permissible reflecting object 20th

Both reflective objects 19, 20 cause a shift the center of the detected by the light receiver 15 Light intensity or a shift of the received light gravity. The position of FIG. 4 found Light centroid is stored as setpoint. If the Operation of the arrangement shown in FIG. 4 an unacceptable reflective or optically opaque object in the surveillance area 6 is inserted, this causes a shift the light gravity, ultimately to produce an object detection signal leads.