LIGHT CURTAIN

Description

[0001] The invention relates to a light curtain according to the preamble of claim 1.

[0002] Such light curtains are generally used to detect objects in a surveillance area. The light curtain comprises a transmitter unit with a transmitting-side housing, in which a series of transmitters emitting light beams is provided. Furthermore, a receiver unit is provided with a receiving-side housing, in which a series of receivers receiving light beams is arranged.

[0003] The transmitter unit and the receiver unit are arranged at opposite edges of the surveillance area so that, when the surveillance area is clear, the light beams from each transmitter strike a corresponding receiver. If an object intrudes into the surveillance area, the beam path of at least one of the transmitters is interrupted. An evaluation unit generates an object detection signal based on the received signals from the receivers.

[0004] Before operating the light curtain, the transmitter unit and the receiver unit must be aligned with each other so that, when the monitoring area is clear, the light beams from each transmitter hit the assigned receiver.

[0005] One difficulty here is that the transmitters generally emit light in the infrared range, which is not visible to the human eye.

[0006] To align the transmitter and receiver units, it is common practice to attach a laser pointer to the transmitter unit as an alignment aid. The laser pointer emits a visible laser beam, which is directed onto the receiver unit. Based on the laser light area projected onto the receiver unit, the receiver unit can be aligned relative to the transmitter unit, or vice versa.

[0007] The disadvantage here is that the laser pointer is an additional device, which requires additional design effort and costs. Another disadvantage is that the laser pointer must be mounted on the transmitter unit, which is cumbersome and time-consuming.

[0008] DE 10 2015 007 354 A1 relates to a method for monitoring the alignment of a light grid consisting of a transmitting unit having a plurality of light sources emitting light beams, each of which is guided along a predetermined beam path along an optical axis, and a receiving unit consisting of a plurality of sensors, each associated with a light source, and a control and evaluation unit. The method comprises the following steps: Emission of at least one isolated light beam by one or more of the light sources. Detection of each isolated light beam by at least one sensor of the receiving unit. Determination of the actual position of the detected light beam at the receiving unit based on the light beam distribution at several neighboring sensors. Determination of the alignment quality of the light grid based on the target position on the receiving unit specified by the optical axis of the respective light beam and the determined actual position of the light beam.

[0009] DE 20 2006 012 454 A1 relates to an optoelectronic sensor with a light transmitter, which comprises at least one transmitting element emitting light signals, and a light receiver arranged at a distance from the light transmitter, which comprises at least one receiving element for receiving the light signals from the transmitting element. An evaluation unit is provided for evaluating the light intensity reaching the receiving element as a measure of the quality of alignment. A filter element is arranged downstream of the transmitting element, the filter element having an inner region that transmits light essentially unhindered, and the inner region is surrounded by a light-attenuating outer region.

[0010] EP 1 437 542 A2 relates to a light grid and a method for adjusting the same. The light grid according to the invention comprises a transmitter unit having a predetermined number of transmitters emitting transmitted light beams, and a receiver unit having a predetermined number of receivers. The transmitters and receivers each form pairs defining beam axes. When the beam path is clear, the transmitted light beams emitted by a transmitter strike the associated receiver, and when at least one beam axis is interrupted due to an object intrusion, an object detection signal can be generated. To adjust the beam axes of the transmitter unit, at least two transmitting elements emitting visible directional beams are provided in predetermined target positions relative to the transmitter, each of which can be aligned with a target mark on the receiver unit.

[0011] DE 20 2019 106 396 U1 relates to a light barrier arrangement comprising a transmitter unit and a receiver unit, wherein the transmitter unit comprises a plurality of transmitters emitting transmitted light beams and the receiver unit comprises a plurality of receivers receiving transmitted light beams. The arrangement also comprises an alignment unit for aligning the transmitter unit and receiver unit. The alignment unit comprises an array of display elements controlled by a sliding chain.

[0012] In DE 10 2006 050 189 A1, a light grid with a transmitting unit and a receiving unit, wherein the transmitting unit has a plurality of light transmitters and an alignment light transmitter, wherein each light transmitter is assigned a light receiver of the receiving unit, which responds to grid light emitted by a light transmitter when the light receiver is aligned within a first radiation angle to the light transmitter and the light transmitter is aligned within a first viewing angle to the light receiver, characterized in that the receiving unit has an alignment light receiver, which responds to alignment light when the alignment light receiver is aligned within a second radiation angle to the alignment light transmitter and the alignment light transmitter is aligned within a second viewing angle to the alignment light receiver,wherein the second beam angle is greater than the first beam angle and / or the second viewing angle is greater than the first viewing angle and wherein the alignment light transmitter and the alignment light receiver are not taken into account by a control of the light grid during operation.

[0013] The invention is based on the object of providing a simple, safe and cost-effective adjustment option for a light curtain of the type mentioned above.

[0014] To achieve this object, the features of the independent claims are provided. Advantageous embodiments and expedient developments of the invention are described in the dependent claims.

[0015] The invention relates to a light curtain for detecting objects in a surveillance area. The light curtain comprises a transmitting-side housing at a first edge of the surveillance area, in which an arrangement of transmitters emitting light beams is provided, and a receiving-side housing at a second edge of the surveillance area, in which an arrangement of receivers is provided. When the surveillance area is clear, the light beams from the transmitters strike the receivers assigned to them, with an object in the surveillance area interrupting the light beams of at least one transmitter. The light curtain further comprises an evaluation unit in which an object detection signal is generated depending on received signals from the receivers. An arrangement of alignment transmitters emitting alignment light beams is provided in a housing.The beam characteristics of at least some of the alignment light beams differ from the beam characteristics of the light beams. Furthermore, evaluation means are provided in which the alignment quality of the light curtain is determined based on the light quantities of the alignment light beams impinging on the alignment receivers. The individual alignment light beams can be distinguished by individual codes being impressed on the alignment light beams and / or by the alignment light beams being emitted individually at different time intervals. This adjustment takes place during an alignment operation. Codes in the form of pulse sequences are impressed on the alignment light beams, with the pulses of the pulse sequences being changed during the alignment operation, with the pulses of the pulse sequences of the alignment light beams being changed, in particular, depending on the current result of the alignment of the light curtain.The alignment mode can be adjusted on the transmitting side, with this setting being transmitted via coding in light beams and / or alignment light beams. Based on the detected coding, the evaluation unit switches to an alignment mode that determines angular errors and / or displacement errors in the alignment of the transmitting-side housing relative to the receiving-side housing by evaluating the received levels of the alignment receivers. The received levels are evaluated selectively for different alignment light beams, and / or intermediate values ​​for angular and / or displacement errors are calculated by evaluating the received levels of neighboring alignment receivers.

[0016] The basic idea of ​​the invention is therefore to arrange alignment transmitters in one of the housings of the light curtain and alignment receivers in the other housing. It is essential that the alignment light beams emitted by the alignment transmitters have beam characteristics, at least some of which differ from the beam characteristics of the light beams of the transmitters. The alignment light beams thus formed generate output signals to the alignment receiver, based on which a measure of the alignment quality can be determined using the evaluation means. In particular, based on the output signals of the alignment receivers in the alignment means, angular or displacement errors of the housings relative to one another can be determined, which can advantageously be signaled to the user in a suitable manner, so that the adjustment of the light curtain can be carried out quickly and precisely.

[0017] According to an advantageous embodiment, alignment transmitters are provided which have different beam directions than the light beams.

[0018] The transmitters' light beams span a monitoring area lying in a single plane due to their array of transmitters. Even slight displacements or rotations prevent the light beams from reaching the assigned receivers, especially since the light beams are typically emitted at small beam angles and the receivers have small aperture angles.

[0019] In contrast, since the alignment transmitters emit their alignment light beams in different directions, it is ensured that even if the transmitter unit is shifted or rotated relative to the receiver unit, some of the alignment light beams at least partially hit the assigned alignment receivers, so that the alignment quality or the existing angular or displacement errors can be determined based on their output signals.

[0020] In principle, the beam angles of the alignment light beams can be dimensioned the same as the beam angles.

[0021] It is particularly advantageous to provide alignment transmitters that have different beam angles compared to the light beams.

[0022] The beam angle sizes can be used to specify the alignment range for adjusting the light curtain. In particular, larger beam angles can increase the alignment range.

[0023] According to an advantageous embodiment, the alignment transmitters are integrated in the transmitting-side housing and the alignment receivers are integrated in the receiving-side housing.

[0024] In this case, at least part of the alignment receivers may be formed by receivers.

[0025] This simplifies the construction of the light curtain.

[0026] In principle, the alignment transmitters can be distributed across the entire height of the transmitter or receiver unit's housing and integrated into the series arrangement of the transmitters or receivers. The same applies to the alignment receivers.

[0027] According to an advantageous embodiment, several alignment light beams are guided via at least one common optical element.

[0028] The alignment transmitters, which emit these alignment light beams, form a compact functional unit with the optical element for aligning the light curtain, which can be arranged locally on the respective housing of the light curtain.

[0029] An optical element can be provided on the transmitting and / or receiving side.

[0030] A tube and / or a lens and / or a diaphragm is expediently provided as the optical element.

[0031] The alignment transmitters can form a row, cross, line or matrix arrangement.

[0032] The alignment transmitters can be arranged on a common substrate such as a circuit board and form a compact unit.

[0033] Likewise, the alignment receivers can form a series, cross, line or matrix arrangement.

[0034] These can also be arranged on a common substrate.

[0035] Alternatively, a single alignment receiver can be provided.

[0036] According to the invention, the individual alignment light beams can be distinguished by the fact that individual codings are imprinted on the alignment light beams and / or that the alignment light beams are emitted individually at different time intervals.

[0037] Due to this distinguishability, the individual alignment light beams and the output signals generated in alignment receivers can be used to determine the alignment quality and also to determine angular and displacement errors.

[0038] According to the invention, the adjustment of the light curtain takes place during an alignment operation.

[0039] This means that the adjustment is limited to defined phases of the light curtain's operation and, in particular, is separated from the monitoring operation in which objects in the monitoring area are detected.

[0040] The alignment light beams can be emitted continuously or only during alignment operation.

[0041] According to the invention, codings in the form of pulse sequences are impressed on the alignment light beams, wherein the pulses of the pulse sequences are changed during the alignment operation.

[0042] In particular, the pulses of the pulse sequences of the alignment light beams can be changed depending on the current result of the alignment of the light curtain.

[0043] In particular, by varying the pulse durations, the sensitivity and range of the alignment light beams for adjustment can be changed. Increasing the pulse durations increases the sensitivity.

[0044] Furthermore, during the alignment process, the alignment light beams allow the angular range for adjusting the light curtain to be wider than without alignment beams.

[0045] In the simplest case, the alignment operation is activated automatically when the light curtain is switched on, i.e. started.

[0046] Furthermore, the alignment operation can be activated by means of switching means on the transmitting side and / or the receiving side.

[0047] A user can then specify when an alignment operation is started by operating the switching devices.

[0048] Advantageously, the alignment mode is activated automatically if the evaluation means detect insufficient alignment of the light curtain.

[0049] This ensures adaptive adjustment of the light curtain to changing boundary conditions.

[0050] Furthermore, it is possible that the alignment mode is activated when predefined codes are detected in light beams or alignment light beams.

[0051] This allows the alignment operation to be initiated by controlling the transmitter operation.

[0052] According to a first advantageous embodiment, the alignment operation is terminated after a predetermined time interval has elapsed.

[0053] This activates the alignment mode for a fixed period of time.

[0054] According to a second advantageous embodiment, the alignment operation is terminated when a predetermined alignment quality of the light curtain is achieved. In this case, the alignment operation is automatically terminated only when the adjustment of the light curtain has been successfully completed.

[0055] According to the invention, the alignment operation can be set on the transmitting side, wherein this setting is transmitted via codings in light beams and / or alignment light beams, and wherein the evaluation unit switches to an alignment mode on the basis of the detected codings.

[0056] According to the invention, angular errors and / or displacement errors of the alignment of the transmitting-side housing relative to the receiving-side housing are determined by evaluating reception levels of alignment receivers.

[0057] By evaluating the reception levels, possible angle and displacement errors can be determined quantitatively.

[0058] It is particularly advantageous to calculate intermediate values ​​for angle and / or displacement errors by evaluating reception levels of neighboring alignment receivers.

[0059] The interpolations performed in this way allow continuous, spatially resolved values ​​for the angular and displacement errors to be derived over the entire height of the housings.

[0060] It is particularly advantageous if the evaluation of the reception levels is carried out selectively for different alignment light beams.

[0061] This increases the spatial resolution of the measurements and thus the accuracy of determining the angular and displacement errors.

[0062] According to an advantageous embodiment, display means are provided by means of which the alignment quality is displayed.

[0063] In particular, the display devices indicate specific misalignments.

[0064] The display means are generally formed as optical display means, for example in the form of visible light emitting light diodes or light emitting diode arrays.

[0065] In order to indicate misalignments such as angular or displacement errors in a spatially resolved manner, the display means are advantageously formed by a multiple arrangement of display elements which can extend over the entire height of a housing of the light curtain.

[0066] The display means can be provided on an outer side of the transmitting and / or receiving side housing.

[0067] According to a structurally advantageous embodiment, the transmitters and alignment transmitters on the one hand and the receivers and alignment receivers on the other hand are each controlled via the same control means, whereby only the transmitters and receivers are used for object detection.

[0068] In particular, the transmitters and alignment transmitters are controlled jointly via a sliding chain, and the receivers and alignment receivers are controlled jointly via a sliding chain.

[0069] Since the same control means are used for both the transmitters and alignment transmitters as well as for the receivers and alignment receivers, this control can be realized with only a few components.

[0070] The design effort can be further reduced by having the display means comprise display elements that are controlled by the receivers and alignment receivers using the same sliding chain.

[0071] According to an advantageous embodiment, the light curtain is designed as a safety sensor and can be used in the field of safety technology, particularly in the field of personal protection. For this purpose, the safety sensor has a fail-safe design. This can be implemented, in particular, by a two-channel evaluation unit in the form of two cyclically mutually monitoring computer units.

[0072] Advantageously, the light curtain designed as a safety sensor has safety outputs, whereby a system is controlled depending on the switching states of the safety outputs.

[0073] The system can pose a hazard to people. The light curtain monitors a hazardous area within the system. The safety outputs are designed to be fail-safe, and for this purpose, they are advantageously configured with two channels.

[0074] The light curtain operates in such a way that, in monitoring mode, the safety outputs are switched on, thus enabling system operation if no object is detected in the monitoring area. The safety outputs are switched off, and system operation is halted if an object is detected in the monitoring area. In alignment mode, the safety outputs are switched off, regardless of whether an object is detected in the monitoring area or not.

[0075] This ensures that the system is in a safe state in which no danger to persons can arise from the system while the light curtain is in alignment mode and therefore cannot perform its monitoring function.

[0076] The invention is explained below with reference to the drawings. They show: Figure 1: Embodiment of the light curtain according to the invention. Figure 2a: First arrangement of alignment transmitters with an associated optical element for the light curtain according to Figure 1 Figure 2b: Top view of the arrangement of alignment transmitters according to Figure 2a . Figure 3a: Second arrangement of alignment transmitters with an associated optical element for the light curtain according to Figure 1 Figure 3b: Top view of the arrangement of alignment transmitters according to Figure 3a . Figure 4a: Third arrangement of alignment transmitters with an associated optical element for the light curtain according to Figure 1 Figure 4b: Top view of the arrangement of alignment transmitters according to Figure 4a . Figure 5a: Fourth arrangement of alignment transmitters with an associated optical element for the light curtain according to Figure 1 Figure 5b: Top view of the arrangement of alignment transmitters according to Figure 5a Figure 6: Fifth arrangement of alignment transmitters with an associated optical element for the light curtain according to Figure 1Figure 7: Sixth arrangement of alignment transmitters for the light curtain according to Figure 1 Figure 8: Seventh arrangement of alignment transmitters for the light curtain according to Figure 1 . Figure 9a:Exemplary design of the light curtain according to Figure 1 with an array of alignment transmitters. Figure 9b: Transmitter unit of the light curtain according to Figure 9a in a top view. Figure 10: Another embodiment of the light curtain according to Figure 1 with an arrangement of alignment transmitters. Figure 11: Another embodiment of the light curtain according to Figure 1 with an arrangement of alignment transmitters. Figure 12: Circuit arrangement for the arrangement of receivers, alignment receivers, and display elements for the light curtain according to Figure 1.

[0077] Figure 1 shows schematically an embodiment of the light curtain 1 according to the invention.

[0078] The light curtain 1 is used for object detection in a surveillance area. The light curtain 1 has a transmitter unit 2 with a transmitter-side housing 2a, in which a series arrangement of transmitters 4 emitting light beams 3 is provided. The transmitters 4, which are formed by light-emitting diodes or the like, emit light beams 3 in the form of light pulses 3a in the infrared range, as for the first transmitter 4 in Figure 1 shown schematically. The transmitters 4 are controlled by a transmitter controller 5.

[0079] The light curtain 1 further comprises a receiver unit 6, in whose receiving-side housing 6a a series arrangement of receivers 7 in the form of photodiodes or the like as well as an evaluation unit 8 are integrated.

[0080] The transmitter unit 2 and the receiver unit 6 are arranged at opposite edges of the monitoring area so that when the monitoring area is clear, the light beams 3 of a transmitter 4 hit the associated opposite receiver 7, as shown in Figure 1 Each transmitter 4 forms a transmitter-receiver pair with the associated receiver 7. The transmitter-receiver pairs are cyclically activated one after the other in a known manner via optical synchronization. In the present case, eight transmitter-receiver pairs are provided. Of course, a light curtain 1 can also have a different number of transmitter-receiver pairs. Likewise, an electrical, in particular wired, connection can be provided between the transmitter unit 2 and the receiver unit 6.

[0081] Objects in the surveillance area are detected by interrupting the beam path of the light beams 3 of at least one transmitter-receiver pair. Figure 1is an object labeled "O".

[0082] In the evaluation unit 8, an object detection signal is generated based on the received signals, which is output via outputs. In this case, the object detection signal is generated as a binary switching signal, whose switching states indicate whether or not an object is present in the monitoring area.

[0083] In this case, the light curtain 1 is designed as a safety sensor and therefore has a fail-safe design. For this purpose, the evaluation unit 8 has a two-channel design consisting of two cyclically monitoring computer units. Furthermore, the outputs are designed as fail-safe, two-channel safety outputs.

[0084] The operation of light curtain 1 is such that, in its monitoring mode, the safety outputs are switched on, thus enabling system operation if no object is detected in the monitoring area. The safety outputs are switched off, thus stopping system operation if an object is detected in the monitoring area.

[0085] Furthermore, the light curtain 1 can be operated in an alignment mode, in which the transmitter unit 2 and the receiver unit 6 are aligned relative to each other. In alignment mode, the safety outputs are switched off, regardless of whether an object is detected in the monitoring area or not.

[0086] For the adjustment of the light curtain 1, alignment light beams 9, 9a - 9e, emitting alignment transmitters 10, 10a - 10e and in the other housing 6a, 2a associated alignment receivers 11, 11a - 11e are provided (which are shown as examples in the Figures 9 to 11 are shown).

[0087] In the following exemplary embodiments, the alignment transmitters 10, 10a - 10e are located in the transmitting-side housing 2a, and the alignment receivers 11, 11a - 11e are located in the receiving-side housing 6a, although this is not mandatory. The alignment transmitters 10, 10a - 10e can be LEDs, while the alignment receivers 11, 11a - 11e can be photodiodes. Receivers 7 can also generally be used as alignment receivers 11, 11a - 11d.

[0088] The alignment transmitters 10, 10a - 10e can be activated during the entire operation or only during alignment operation. Alternatively, the alignment transmitters 10, 10a - 10e can be activated during the entire operation of the light curtain 1. The alignment light beams 9, 9a - 9e are used only for adjusting the light curtain 1, not for detecting objects in the monitoring area.

[0089] The Figures 2a, 2b show a first arrangement of alignment transmitters 10, which in the present case are placed on a common printed circuit board 12.

[0090] The alignment transmitters 10 emit alignment light beams 9 in different beam directions. The beam angles of the alignment light beams 9 can be the same or different. The alignment light beams 9 are guided over a common optical element, which in the present case is formed by a lens 13 and a diaphragm 14. These elements are located in a tube 15 with several individual diaphragms 15a. The tube 15 is also a component of the optical element. On the receiving side, a corresponding arrangement of alignment receivers 11 with an upstream optical element can be provided. Such receiving arrangements for alignment receivers 11 can also be used for the exemplary transmitter arrangements of the alignment transmitters 10 according to the Figures 2a, 2b , 3a, 3b , 4a, 4b , 5a, 5b , 6 , 7, 8and also be provided with apertures 14 and lenses 13. The reception directions are then opposite to the illustrated transmission beams of the transmitter arrangements. Generally, only one alignment receiver 11 with an upstream optical element can be provided.

[0091] It is advantageously provided that the individual alignment light beams 9 are distinguishable by the fact that individual codings are impressed on the alignment light beams 9 and / or that the alignment light beams 9 are emitted individually at different time intervals.

[0092] This allows the individual alignment light beams 9 to be clearly identified. Evaluation means, which are advantageously integrated into the evaluation unit 8, evaluate the output signals, i.e., the reception levels of the alignment receivers 11, to determine any misalignments of the housings 2a, 6a, in particular rotations or displacements relative to one another, and from this, the alignment quality.

[0093] These characteristics are displayed via suitable display means on the outside of the housing 2a, 6a so that a user can adjust the light curtain 1.

[0094] Advantageously, 9 codings in the form of pulse sequences are impressed on the alignment light beams, whereby the pulses of the pulse sequences are changed during the alignment operation.

[0095] In particular, the change in the pulses of the pulse sequences of the alignment light beams 9 depends on the current result of the alignment of the light curtain 1.

[0096] This allows the sensitivity of the alignment to be optimized.

[0097] The alignment transmitters 10 according to the Figures 2a, 2b form a linear array extending in the longitudinal direction of the housing 2a. Accordingly, this arrangement can only detect and correct misalignments in one spatial direction.

[0098] The Figures 3a, 3b and 4a, 4b show cross-shaped arrangements of alignment transmitters 10, with a transmitter 4 provided at the center of the respective evaluation. Each arrangement of transmitters 4 is assigned an optical element formed by a single lens 13.

[0099] With these arrangements, the light curtain 1 can be aligned in two spatial directions.

[0100] The Figures 5a, 5b and Figure 6 show further lens arrangements of alignment transmitters 10, to which only one lens 13 is assigned as an optical element. The arrangement according to the Figures 5a, 5bcomprises only two alignment transmitters 10, which are located on either side of a transmitter 4. The arrangements can extend in the longitudinal and transverse directions of the housing 2a.

[0101] The Figures 7, 8 show further arrangements of alignment transmitters.

[0102] The alignment mode can be activated, i.e. started, automatically when the light curtain 1 is switched on.

[0103] Furthermore, the alignment mode can be activated automatically if the evaluation means detect an insufficient alignment of the light curtain 1.

[0104] Furthermore, the alignment operation can be activated by means of switching means on the transmitting side and / or the receiving side.

[0105] Finally, the alignment mode can be activated when predefined codes are detected in light beams 3 or alignment light beams 9.

[0106] The alignment operation can be terminated after a specified time interval has elapsed.

[0107] Alternatively, the alignment operation is terminated after a specified time interval has elapsed or the alignment operation is terminated when a specified alignment quality of the light curtain 1 is achieved.

[0108] Advantageously, the evaluation unit 8 controls the alignment operation. The transmitter control unit 5 can also control the alignment operation.

[0109] For example, it is possible for the alignment mode to be adjustable on the transmitting side, for this setting to be transmitted via codings in light beams 3 and / or alignment light beams 9, and for the evaluation unit 8 to switch to an alignment mode based on the detected codings.

[0110] The Figures 9a, 9bshow an embodiment of the light curtain 1 in which an alternating sequence of transmitters 4 and alignment transmitters 10a-10d is provided in the housing 2a. Accordingly, an alternating sequence of receivers 7 and alignment receivers 11a-11d is provided in the housing 6a, so that when the light curtain 1 is aligned, each transmitter 4 is opposite a receiver 7 and each alignment transmitter 10a-10d is opposite an alignment receiver 11a-11d. The display means are formed by individual display elements 16, with each alignment receiver 11a-11d being assigned a display element 16 and emitting a visible optical signal that depends on the quantity of light from specific alignment light beams 9a-9d incident on the assigned alignment receiver 11a-11d and is thus a measure of the alignment quality.

[0111] The alignment transmitters 10a - 10d again emit alignment light beams 9a - 9d with different codings that can be clearly identified in the alignment receivers 11a - 11d.

[0112] How Figure 9b shows, the individual alignment transmitters 10a - 10d emit alignment light beams 9a - 9d in different radiation directions, which are offset in a plane transverse to the longitudinal direction of the housing 2a.

[0113] Depending on how strongly the longitudinal axes of the housings 2a, 6a are rotated relative to each other, only some of the alignment light beams 9a - 9d of the alignment transmitters 10a - 10d hit the respective associated alignment receiver 11a - 11d.

[0114] From this, the angular rotation of the housings 2a, 6a relative to each other can be determined in the evaluation unit 8 and displayed on the display elements 16a - 16c.

[0115] Figure 10 shows a variant of the light curtain 1 according to the Figures 9a, 9bIn this case, the alignment transmitters 10a - 10d emit alignment light beams 9a - 9d, whose beam directions are offset in the plane of the monitoring area. This allows the inclination of the housings 2a, 6a to be detected, which in Figure 10 for an inclination of the housing 6a.

[0116] Figure 11shows a further variant of the light curtain 1. There, only the alignment transmitters 10a - 10e and alignment receivers 11a - 11e with the associated display elements 16 are shown, but not the transmitters 4 and receivers 7 of the light curtain 1. In this case, the radiation directions of the alignment light beams 9a - 9e run parallel to the beam axes of the light beams 3 of the transmitters 4. The radiation angles, i.e., the opening angle 17, shown as an example for the alignment light beams 9c, are enlarged compared to the radiation angles of the transmitters 4. The alignment light beams 9a - 9e are cyclically activated one after the other, whereby individual coding can again be imprinted on them.

[0117] With this arrangement, in particular displacements of the housings 2a, 6a as in Figure 11 shown.

[0118] Figure 11shows the situation when the alignment transmitter 10c is activated. The alignment light beams 9c of the alignment transmitter 10c completely illuminate the alignment receiver 11b, partially illuminate the alignment receiver 11a, very slightly illuminate the alignment receiver 11c, and not illuminate the alignment receivers 11d, 11e at all.

[0119] From these illumination patterns, the degree of displacement can be determined, which is displayed by the display elements 16.

[0120] According to an advantageous embodiment, the transmitters 4 and alignment transmitters 10a - 10e on the one hand and the receivers 7 and alignment receivers 11, 11a - 11e on the other hand are each controlled via common control means.

[0121] An example of this shows Figure 12 .

[0122] In this arrangement, a controller 18 is provided that controls both the receivers 7 and the alignment receivers 11, which are connected to the controller 18 via a line 19. The display elements 16a-16c assigned to the alignment receivers 11a-11c are also controlled by the controller 18.

[0123] The controller 18 can be integrated into the evaluation unit 8.

[0124] A shift chain 20 with eight shift chain elements 20a-20h, formed, for example, by flip-flops, is provided to control the receivers 7 and the alignment receivers 11. Under the control of the controller 18, a bit value, such as a "1," is shifted through the shift chain elements 20a-20h, thereby activating the receivers 7 and the alignment receivers 11 one after the other.

[0125] This shift chain 20 is also used to control the display elements 16a-16c. Each display element 16a-16c is assigned a display memory element 21a-21c, which is formed by a flip-flop. Control and addressing are performed via control lines 22, 23, 24 via the controller 18 such that when the first display memory element 21a is activated via the shift chain element 20a, the second display memory element 21b is activated via the shift chain element 20d, and the third display memory element 21c is activated via the shift chain element 20g.

[0126] In addition, information is stored in the display memory elements 21a - 21c as to how, upon activation of the respective display memory element 21a - 21c, the associated display element 16a - 16c emits visible light with a specific flashing sequence, wherein the respective flashing sequence signals the current alignment quality.

[0127] In an alternative embodiment, the information change of the display elements 16a, 16b, 16c can also be carried out via one of the control lines 22, 23, 24.

[0128] In a further embodiment, the information change of the display elements 16a, 16b, 16c and thus the flashing sequence can be carried out by continuously changing the contents of the memory elements 21a - 21c via the control lines 22, 23, 24.

[0129] A corresponding control is provided on the transmitter side, whereby the transmitters 4 and alignment transmitters 10 are controlled by a sliding chain 20. List of reference symbols

[0130] (1)Light curtain (2)Transmitter unit (2a)Housing (3)Light beams (3a)Light pulses (4)Transmitter (5)Transmitter control (6)Receiver unit (6a)Housing (7)Receiver (8)Evaluation unit (9)Alignment light beam (9a - 9e)Alignment light beam (10)Alignment transmitter (10a - 10e)Alignment transmitter (11)Alignment receiver (11a - 11e)Alignment receiver (12)Printed circuit board (13)Lens (14)Aperture (15)Tube (15a)Individual apertures (16)Display element (16a - 16c)Display element (17)Opening angle (18)Controller (19)Cable (20)Sliding chain (20a - 20h)Sliding chain element (21a - 21c)Display memory element (22)Control line (23)Control line (24)Control line OObject

Claims

1. A light curtain (1) for detecting objects in a monitoring area, with a housing (2a) on the transmitting side at a first edge of the monitoring area, in which an arrangement of transmitters (4) emitting light beams (3) is provided, with a housing (6a) on the receiving side at a second edge of the monitoring area, in which an arrangement of receivers (7) is provided, the light beams (3) of the transmitters (4) impinging on receivers (7) assigned to them when the monitoring area is free, and an object in the monitoring area interrupting the light beams (3) of at least one transmitter (4), and with an evaluation unit (8), in which an object detection signal is generated as a function of received signals from the receivers (7), an arrangement of alignment transmitters (10, 10a - 10e) emitting alignment light beams (9, 9a - 9e) being provided in a housing (2a, 6a), the beam characteristics of at least some of the alignment light beams (9, 9a - 9e) are different from the beam characteristics of the light beams (3), and evaluation means are provided in which the alignment quality of the light curtain (1) is determined on the basis of light quantities of alignment light beams (9, 9a - 9e) impinging on the alignment receivers (11, 11a - 11e), the alignment of the light curtain (1) being carried out by selecting an alignment mode, characterised in that the individual alignment light beams (9, 9a - 9e) can be distinguished in that the alignment light beams (9, 9a - 9e) are imprinted with individual codes, and / or in that the alignment light beams (9, 9a - 9e) are emitted individually at different time intervals, in that the alignment light beams (9, 9a - 9e) are imprinted with codes in the form of pulse sequences, wherein the pulses of the pulse sequences are changed in the course of the alignment operation, wherein in particular the change in the pulses of the pulse sequences of the alignment light beams (9, 9a - 9e) takes place depending on the current result of the alignment of the light curtain (1), in that the alignment operation is adjustable on the transmitter side, in that this setting is transmitted via codes in light beams (3) and / or alignment light beams (9, 9a - 9e), and in that the evaluation unit (8) switches to an alignment mode on the basis of the codes detected, in that angle errors are detected by evaluating reception levels of alignment receivers (11, 11a - 11e), angular errors and / or displacement errors of the alignment of the transmitter-side housing (2a) relative to the receiver-side housing (6a) are determined, in that the evaluation of the reception levels is carried out selectively for different alignment light beams (9, 9a - 9e), and / or in that intermediate values for angular and / or displacement errors are calculated by evaluating reception levels of neighbouring alignment receivers (11, 11a - 11e).

2. A light curtain (1) according to claim 1, characterised in that alignment transmitters (10, 10a - 10e) are provided which have different beam directions and / or beam angles relative to the light beams (3).

3. A light curtain (1) according to one of claims 1 or 2, characterised in that the alignment transmitters (10, 10a - 10e) are integrated in the housing (2a) on the transmitting side and the alignment receivers (11, 11a - 11e) are integrated in the housing (6a) on the receiving side.

4. A light curtain (1) according to claim 3, characterised in that at least some of the alignment receivers (11, 11a - 11e) are formed by receivers (7).

5. A light curtain (1) according to one of claims 1 to 4, characterised in that the reception characteristics and / or reception directions of the alignment receivers (11, 11a - 11e) are different from one another and / or are different from the reception characteristics and / or reception directions of the receivers (7).

6. A light curtain (1) according to one of claims 1 to 5, characterised in that several alignment light beams (9, 9a - 9e) are guided via at least one common optical element.

7. A light curtain (1) according to claim 6, characterised in that an optical element on the transmitting and / or receiving side is provided, wherein a tube (15) and / or a lens (13) and / or an aperture (14) is provided as the optical element.

8. A light curtain (1) according to one of claims 1 to 7, characterised in that the alignment mode is activated by means of switching means on the transmitting side and / or receiving side, or in that the alignment mode is activated when the light curtain (1) is switched on, or in that the alignment mode is activated automatically when the evaluation means detect an insufficient alignment of the light curtain (1), or in that the alignment mode is activated when predetermined codings in light beams (3) or alignment light beams (9, 9a - 9e) are recognised.

9. A light curtain (1) according to one of claims 1 to 8, characterised in that the alignment operation is terminated after a predetermined time interval has elapsed, or in that the alignment operation is terminated when a predetermined alignment quality of the light curtain (1) has been achieved.

10. A light curtain (1) according to one of claims 1 to 9, characterised in that the alignment light beams (9, 9a - 9e) are emitted permanently or only during the alignment mode, and / or in that the alignment mode is controlled via the evaluation unit (8) or via a transmitter control (5).

11. A light curtain (1) according to one of claims 1 to 10, characterised in that alignment means are present as a component of the evaluation unit (8).

12. A light curtain (1) according to one of claims 1 to 12, characterised in that display means are provided, by means of which the alignment quality is displayed, and / or in that specific misalignment positions are displayed with the display means, the display means being provided on an outer side of the housing (2a, 6a) on the transmitting side and / or receiving side.

13. A light curtain (1) according to one of claims 1 to 12, characterised in that the alignment transmitters (10, 10a - l0e) and / or alignment receivers (11, 11a - 11) form a row, cross, line or matrix arrangement, or in that a single alignment receiver (11) is provided.

14. A light curtain (1) according to one of claims 1 to 13, characterised in that the transmitters (4) and alignment transmitters (10, 10a - l1e) on the one hand and the receivers (7) and alignment receivers (11, 11a - 11e) on the other hand are each controlled via the same control means, whereby only the transmitters (4) and receivers (7) are used for object detection.

15. A light curtain (1) according to claim 14, characterised in that the transmitters (4) and alignment transmitters (10, 10a -10e) are jointly controlled via a sliding chain (20), and in that the receivers (7) and alignment receivers (11, 11a - 11e) are jointly controlled via a sliding chain (20).

16. A light curtain (1) according to one of claims 14 or 15, characterised in that the display means comprise display elements (16, 16a - 16c) which are controlled with the receivers (7) and alignment receivers (11, 11a - 11e) by means of the same sliding chain (20).

17. A light curtain (1) according to one of claims 1 to 16, characterised in that this is a safety sensor, wherein this has safety outputs, wherein a system is controlled depending on the switching states of the safety outputs.

18. A light curtain (1) according to claim 17, characterised in that in its monitoring mode the safety outputs are switched on and thus the operation of the system is enabled if no object is detected in the monitoring area, and in that the safety outputs are switched off and thus the operation of the system is stopped if an object is detected in the monitoring area, and in that in alignment mode the safety outputs are switched off irrespective of whether an object is detected in the monitoring area or not.