Opto-electronic sensor

p0001The invention relates to an opto-electronic sensor according to the preamble of claim 1.

p0002Such sensors are used for example as a simple light barriers or multi-beam light grid systems for access control, in particular dangerous machine working zones or specific spaces should be secured within a building.

p0003If in sensors of the type mentioned an object enters the monitored zone, and thus interrupts the light path between the light transmitter and light receiver, an object detection signal is generated, which can for example lead to the shutdown of a machine or to trigger an audible or visual warning process.

p0004In known systems based the decision on whether the light path between transmitter and receiver is interrupted or not, as a rule, on a purely energetic consideration, which means that whenever the amount of light received falls below a certain value, and the interruption of the light path thus deduce the presence of an object in the surveillance area.

p0005A problem with known systems is the fact that in certain applications, reflective objects can be located within the transmission angle of the light transmitter or within the visual field of the light receiver, which are generally permitted, so should trigger no object detection signal, however, can result in an invalid object is umspiegelt in the monitoring area. In such a mirroring, for example, the central light beam between the light transmitter and light receiver be interrupted by an illegal object, but are passed through the specified permissible reflecting objects still so much light on the light receiver that the critical light quantity value is not undershot and consequently generating an object detection signal is omitted. In the known sensors can not be guaranteed so that all present in the monitored area impermissible objects are reliably detected.

p0006From the <patcit id="pcit0001" dnum="WO8911710A"><text>WO-A-89/11710</text></patcit> is a known sensor, the light receiver is formed as ortsauflisendes receiving element. However, in the position of the light signal is only defined by the element of the strongest light incidence.

p0007From the <patcit id="pcit0002" dnum="DE4119797C2"><text>DE 4119797C2</text></patcit>. <patcit id="pcit0003" dnum="DE3513671C3"><text>DE3513671C3</text></patcit>. <patcit id="pcit0004" dnum="DE4040225C2"><text>DE4040225C2</text></patcit> and <nplcit id="ncit0001" npl-type="s"><text>H.-T. Meinert "background suppression with light sensors" in Feinwerktechnik &amp; Messtechnik 97 (1989) 6, pp 261-264</text></nplcit> are known triangulation sensors with ortsautlösendern light receiver.

p0008An object of the invention is to develop an optoelectronic sensor of the aforementioned type such that its reliability is increased, in particular, the disturbing influence of permissible reflecting objects near the monitor area or in the surveillance area should be even eliminated.

p0009This object is achieved by an optoelectronic sensor having the features of claim 1.

p0010According to the invention is used as light receiver no longer a simple photodiode used for example according to prior art is used, but it is instead a spatially resolving receiver element is used, which has a light-sensitive surface, wherein the spatially resolving receiver element is designed so that the position of the received light center of gravity on the photosensitive area can be determined. a desired position is specified for the position of the received light center of gravity on the photosensitive surface of the receiving element, which is compared in the operation of the inventive sensor with the determined actual positions. the position of the received light center of gravity is moved to the photosensitive surface by introducing an unacceptable object in the monitoring area, wherein an object detection signal is generated when this shift of the detected during operation of the sensor position relative to the desired position exceeds a defined threshold value.

p0011According to the inventive principle, the recognition of a present in the monitored area impermissible object is therefore also possible if even permissible reflecting objects are arranged in the vicinity of the monitored zone or in the surveillance area that a significant proportion of the light emitted from the light emitter amount even when disconnected from the central light beam is passed through an illegal object to the light receiver, ie when the permissible objects lead to a mirroring of unauthorized object. The reliability of the sensor according to the invention is thus significantly improved over known from the prior art sensors.

p0012One advantage of the sensor according to the invention is further that a more flexible application range is given as sensors according to the invention can be installed very close to permissible reflecting objects without adversely affect these reflective objects in the reliability of the sensor.

p0013Another advantage is that in the production of an inventive sensor not very precise adjustment of the individual optical components is necessary to each other or that expensive opto-mechanical components can be used as one target value is determined for each produced sensor after completion of the production process, which then automatically transmits all inaccuracies bill encountered in production. Reference is illustrative noted that in the production occurring inaccuracies only result in the desired position of the received light gravity is shifted to the light-sensitive surface against an ideal sensor mounted, but this has no adverse effects, since simply the shifted target position than actual target position can be stored, which is then - as already mentioned - automatically takes into account all inaccuracies.

p0014It is preferred if the spatially resolving Empfangselem is ent consists of a linear array of a plurality of photosensitive elements. However, it is also possible to provide more light-sensitive elements in a matrix arrangement, said matrix then forms the light-sensitive area of the entire receiving element. When using a linear array, that is a one-dimensional-receiving element, such Umspiegelungen may be detected or eliminated, which take place within a plane which is at least substantially extends parallel to the row arrangement of the receiving element forming light-sensitive elements. When using a matrix arrangement, however, any Umspiegelungen may be detected or eliminated which occur in an arbitrary plane that is parallel to the optical axis of the overall sensor system.

p0015When using an array of individual photosensitive elements, offers the use of CCDs.

p0016The individual light-sensitive elements of a row or matrix arrangement can for example be designed as a photodiode or other, for detecting light signals proper elements.

p0017Particularly however, it is also possible in the present invention provided for spatially resolving receiver element as a one or two dimensional PSD, that form as a position-sensitive detector. A position sensitive detector is an electro-optical element comprising a light sensitive surface, the detector provides, for example, two streams, be concluded from the amplitude ratio to a dimension related to position of a light spot on the photosensitive surface of the PSD. If a four streams donating PSD is employed, from the amplitude ratio of these currents to one another on the two. Dimensions related position of a light spot on the photosensitive surface of the PSD to be closed.

p0018, when a desired position of the received light gravity by means of a teach-in procedure, identifiable and can be stored is particularly advantageous. In this case, the inventive sensor can be individually adapted to the given conditions at any location. In carrying out the teach-in procedure at the installation position of the received light spot is already affected by any existing, permitted, reflecting objects. Consequently, when the to be stored target position is determined as part of the teach-in process so that a light signal is transmitted in the free of illegal objects monitoring area and received again, sets the position of caused by this light signal light spot on the photosensitive surface of the on the individual circumstances coordinated setpoint value. The end user of the inventive sensor is thus by means of said teach-in process to be able to make an individual adaptation to the respective conditions of use, without these conditions must be taken into account already in the manufacturing process of the sensor. This allows a wide variety of uses of the inventively designed sensor.

p0019The spatially resolving receiver element of the sensor can be disposed in the region of the focal point of an imaging optical receiving system, which due to the current through said teach-in process learning ability of the sensor does not have to be taken precisely to the adherence to the exact position of the receiving element at the focus here in particular. It is quite conceivable that the spatially resolving receiver element with respect to the imaging optical receiving system is arranged intra- or extrafocally.

p0020Light transmitters and light receivers may be disposed on opposite sides of the surveillance area. Alternatively, it is possible to provide light transmitters and light receivers on the same side of the monitored region and a retroreflector on the opposite side of the surveillance area. The latter variant corresponds to an auto-collimation.

p0021The inventive sensor can also be used as part of a light grid arrangement, in which case each include a plurality are disposed of juxtaposed light transmitters and light receivers in the structure required in each case.

p0022the light receiver of the light grid arrangement are preferably designed as a one-dimensional receiver elements. This one-dimensional receiver elements can be arranged rotated one another, the axis of rotation corresponds to that axis which connects together mutually associated light-emitters and light receivers. It is advantageous, when the twist angle between adjacent receiver elements amounts to 90 °. In this way, a light grid arrangement in this invention is able to delektieren or eliminate that occur in any plane which is parallel to said Verdrehachsen any Umspiegelungen. Thus, although only one-dimensional receiver elements are used, any Umspiegelungen can be eliminated due to the aforementioned rotation.

p0023In a method for operating an inventive sensor, one or more to be stored desired positions - are determined by the sensor is operated at the site under conditions where an object-free monitored region - as already mentioned. The monitoring range function may very well have permitted reflective objects, it may simply be no illegal objects exist in determining the desired position. If different conditions are possible at a work, a set value can be determined and stored for each of these conditions, in which case the different desired positions can be activated for example by means of a selector switch. Alternatively, it is also possible to activate all the stored desired positions simultaneously, so that only an object detection signal is issued when the actual position of all the determined target positions deviated in a respective predetermined level.

p0024The actual and target positions can be detected and processed in the form of a Dimension representing values ​​or in the form of two dimensions representing coordinate values.

p0025When using at least two partial streams receiving member yielding (PSD), in which the partial streams characterize the position of the received light gravity, can be used as the determined position quantity characterizing the quotient be processed from a partial flow and the total flow of the partial streams. In this way permissible reflections can be distinguished very well from undue reflections, which is not the case with conventional PSD calculation algorithms where usually the ratio between the difference of two sub-streams and their total current is formed.

p0026It is also advantageous if, in a method for operating a system according to the invention having a plurality of light transmitters and light receivers in light grid arrangement, a uniform shift of the received light focuses all light receiver is classified as permissible Systemdejustage or as permissible low frequency vibration, so that in these cases not express an object detection signal takes place. In this way, higher system availability, ie a lower susceptibility to interference of the system guarantees.

p0027It is preferred if the presence of the spatially resolving receiver element is additionally used to compensate for inevitable opto-mechanical system tolerances in light gratings. Such system tolerances are, for example due to the twist of the mounting profiles used for light curtains, through wedge errors in lenses through decentered layers of screens, etc. In order to bring the said compensation, as part of a calibration process, the target position for each spatially resolving receiver element is determined separately and for example, jointly backed by a corresponding shift allowable tolerance. So it can be achieved that the inventive light curtain system complies with the existing safety standard according to claims with respect to the pivot angle and simultaneously accept a maximum adjustment range for the end user.

p0028Finally, it is in a method for operating a sensor according to the invention advantageous when an object detection signal is always outputted when either the deviation of the determined actual position from the stored desired position exceeds the defined threshold or when the received by the light receiver light amount a defined minimum value below. can be found In the extreme case where the light receiver, for example, receives absolutely no or very little light, and consequently no actual position of the light spot occurrence, it is thus possible to generate an object detection signal, as in this case, received by the light receiver Luminance a defined minimum value falls below.

p0029Further preferred embodiments are defined in the dependent claims. The invention includes arbitrary combinations of the sub-claims, in particular also of the method claims among each other.

p0030The invention is described below based on embodiments with reference to the drawings; in which:<dl id="dl0001"><dt>Fig. 1</dt><dd>a schematic diagram of a sensor assembly according to the invention without reflective objects in the monitoring area or near the monitor area,</dd><dt>FIG. 2</dt><dd>a schematic diagram of a sensor assembly according to the invention with a permissible reflecting object near the surveillance area,</dd><dt>Fig. 3</dt><dd>a schematic diagram of a sensor assembly according to the invention with a permissible reflecting object near 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 autocollimation with a permissible reflecting object near the surveillance area and another permissible reflecting object in the surveillance area.</dd></dl>

p0031<figref idrefs="f0001">Fig. 1</figref> shows a designed as a LED light emitter 1, which emits a light beam towards an optical transmitting system. 2 The optical axis 3 of the transmitting optical system 2 coincides with the optical axis of an optical reception system 4, on which the transmission optics 2 side remote designed as a PSD light receiver 5 is provided.

p0032the monitoring range is 6. between the transmitting optical system 2 and the optical receiving system. 4

p0033The spatially resolving light receiver 5 provides a dependent of the position of the incident thereon light spot signal to an evaluation circuit 7, which equipped with a storage element 8 for storing a target position and with a means 9 for comparing the nominal position with a determined actual position is.

p0034The transmission optical system 2 focuses the light emitted by the light transmitter 1 light such that a large part of this light is directed parallel to the optical axis 3 to the receiving optical system 4th A part of the light emitted by the light transmitter 1 the light is radiated, however, inclined to the optical axis 3 and thus does not enter the receiving optics 4. This situation is out of the in<figref idrefs="f0001">Fig. 1</figref> depicted arrows show which illustrate the light paths described.

p0035When in <figref idrefs="f0001">Fig. 1</figref> shown operating position of the sensor. are neither permitted nor prohibited reflective objects in the monitoring area 6 or near the monitored zone 6, so that the light emitted by the light transmitter 1 light unaffected reaches of such objects on the light receiver. 5 The light spot formed on the light receiver 5 is located under<figref idrefs="f0001">Fig. 1</figref> Thus in its zero position, which is illustrated by the numeral 10th This zero position 10 is preferably located in the center of the light-sensitive surface of the light receiver fifth

p0036The operating status in accordance <figref idrefs="f0001">Fig. 1</figref> is therefore adapted to determine a target position of the light spot imaged on the light receiver 5, wherein said target position of the zero position 10 corresponds. This target position can be stored in the memory element 8 of the evaluation circuit 7, so that it is available for later comparison with actual positions available.

p0037<figref idrefs="f0001">FIG. 2</figref> shows the arrangement according <figref idrefs="f0001">Fig. 1</figref>Wherein below the monitoring area 6 a permissible reflecting object 11 here is additionally present; the reflecting surface extends parallel to the optical axis 3 and facing the surveillance area. 6

p0038In the <figref idrefs="f0001">FIG. 2</figref> arrows shown illustrate that a part of the light emitted by the light transmitter 1 light incident on the reflecting surface of the allowable reflecting object 11 and passes from there to the receiving optics. 4 The receiving optical system 4 focuses the light reflected by the reflecting object 11 permissible light such that a second spot of light at the position marked with 12 is formed on the photosensitive surface of the light receiver 5, which is spaced from the null position 10th

p0039The evaluation circuit 7 is to calculate the location, the center of the light intensity of the two located at the zero position 10 and at position 12 light spots. In this calculation includes a both the positions of the two light spots and each received in the two light spots amounts of light. Thus, there is a distance X of such averaged center of the light intensity of the zero position 10. The distance X is less than the distance of the position 12 of the zero position 10th

p0040The distance X thus indicates a desired position of the sum of the light spots received under the operating conditions in accordance with <figref idrefs="f0001">FIG. 2</figref> with a permissible reflecting object 11 in the vicinity of the monitored zone 6. It is possible to use this target value in accordance with, in addition to the <figref idrefs="f0001">Fig. 1</figref> save determined nominal value as another setpoint. It is also possible, according to the only<figref idrefs="f0001">FIG. 2</figref> save determined nominal value. For storage of two nominal values ​​the generation of an object detection signal is carried out whenever the determined actual value of both setpoints is different.

p0041<figref idrefs="f0001">Fig. 3</figref> shows the arrangement according <figref idrefs="f0001">FIG. 2</figref> with the difference that now an invalid object 13 is present in the monitoring area 6, which is to prevent that light from the transmitting optical system 2 enters parallel to the optical axis 3 to the receiving optical system 4 optically opaque.

p0042It passes under <figref idrefs="f0001">Fig. 3</figref> however, continues to be a part of the emitted light from the light transmitter 1 to the reflecting surface of the allowable object 11, from where this portion of light to the receiving optics 4 is directed. correspondingly<figref idrefs="f0001">FIG. 2</figref> pools the receiving optics 4 in this way, the received light component and therefore causes the formation of a light spot at the position 12 on the light receiver 5. Now, when the evaluation circuit 7 under the conditions <figref idrefs="f0001">Fig. 3</figref> in turn, determines the center of the light intensity of the received light spots, so the position is not subject to the <figref idrefs="f0001">Fig.2</figref> differ determined position, since according to <figref idrefs="f0001">Fig. 3</figref> at the zero position 10 no light spot is received due to the existing illegal object. 13 The under<figref idrefs="f0001">Fig. 3</figref> determined the center of the light intensity is thus coincide in terms of its position with the position 12, which describes the location of that light spot, is what caused the bypass light on permissible reflecting object 11th The center of the light intensity thus has according to<figref idrefs="f0001">Fig.3</figref> a distance Z from the zero position 10, which from the distance X according <figref idrefs="f0001">FIG. 2</figref> is different.

p0043If now in the evaluation circuit 7 in the comparison means 9 in accordance with the <figref idrefs="f0001">Fig. 1 and 2</figref> stored desired positions with the actual position according to <figref idrefs="f0001">Fig. 3</figref> are compared, it can be determined that the deviation Z no setpoint corresponds, so that it can be concluded in the monitoring area 6 in the presence of an object or an unacceptable object.

p0044Despite accordance <figref idrefs="f0001">Fig. 3</figref> held and caused by the permissible object 11 bypass light can thus be 13 reliably detected the illegal object. It can not - happen that the bypass light leads to the object 11 that a sufficient amount of light is received and alone because of this fact does not occur, the delivery of an article detection signal - as in the prior art.

p0045<figref idrefs="f0002">Fig. 4</figref> shows an optoelectronic sensor of the invention in auto-collimation. Light transmitter 14 and light receiver 15 are arranged on one side of a monitored zone 6, while on the opposite side of the monitored region 6, a retroreflector 16 is provided which has two Spieqel 17, 18 which cause a deflection of the light emitted from the light emitter 14 light beam back to the light receiver 15 , Instead of the retroreflector 16 can also be provided Tripelspiegelsystem.

p0046In monitoring area 6 a permissible reflecting object 19 is arranged. Above the monitoring area 6 another permissible reflecting object 20 is arranged.

p0047Both reflective objects 19, 20 cause a shift of the center of the detected by the light receiver 15 light intensity or a shift of the received light gravity. The position of the under<figref idrefs="f0002">Fig. 4</figref> detected light centroid is stored as setpoint. If according to the operation of the arrangement<figref idrefs="f0002">Fig. 4</figref> an unacceptable reflective or optically opaque object is introduced into the monitored zone 6, this causes a shift of the optical center of gravity, which ultimately results in the creation of an object detection signal.