LIGHT BORDER ARRANGEMENT

Description

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

[0002] In the simplest case, the light barrier arrangement consists of a single light barrier, i.e. the transmitter unit of the light barrier arrangement has only one transmitter emitting light, to which only one receiver in the receiver unit of the light barrier arrangement is assigned.

[0003] In general, the light barrier arrangement can also comprise several individual light barriers. In particular, the light barrier arrangement can be designed as a light curtain, in which several transmitters are integrated into a first housing of the transmitter unit and several receivers are integrated into a second housing of the receiver unit.

[0004] Generally, the transmitter unit and the receiver unit are arranged at opposite edges of a monitoring area within which the light barrier array detects objects. Before operating the light barrier array, the transmitter unit and the receiver unit must be aligned with each other so that, when the monitoring area is clear, the transmitted light from each transmitter hits 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 comprising 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 formed by a plurality of sensors, each associated with a light source, and a control and evaluation unit. The method comprises the following method 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 in the receiving unit. Determination of an 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. In the control and evaluation unit, the sensors illuminated by a light beam measure and determine the intensity based on the pulse width of the signal from the respective sensor.

[0009] DE 101 17 838 A1 relates to a method for suppressing stray light in optical measuring devices with a light transmitter and a light receiver. The light signal emitted by the light transmitter comprises light pulses. The light pulses are arranged in spaced-apart pulse packets and follow one another within a pulse packet at a carrier frequency. Immediately after receiving the light signal and converting it into an electrical signal, the electrical signal is bandpass filtered in the range of the carrier frequency in the light receiver.

[0010] EP 0 598 630 A1 discloses a light barrier arrangement with display means comprising multiple display elements, wherein the display elements indicate the alignment quality of different receivers. The display element is spatially assigned to the receiver(s) whose alignment quality it indicates. The display elements are addressed and controlled by means of a sliding chain.

[0011] DE 44 23 264 A1 relates to an optoelectronic device for transmitting data words in the form of bit sequences, comprising a transmitter emitting a transmitted light beam and a receiver, wherein the bit sequences are imprinted on the transmitted light beam in the form of a code. During transmission pauses in which no data words are transmitted, monitoring transmitted light pulses are transmitted within predetermined time intervals with a code different from the data words and designed as a pulse sequence such that the average transmission power does not exceed a predetermined threshold. If a number of monitoring transmitted light pulses are not detected in the receiver, the transmitter's transmission power is reduced.

[0012] The invention is based on the object of providing a simple, safe and cost-effective adjustment option for a light barrier arrangement of the type mentioned above.

[0013] 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.

[0014] The invention relates to a light barrier arrangement comprising a transmitter unit having at least one transmitter emitting light pulses, a receiver unit having at least one receiver, and an alignment unit for aligning the transmitter unit and receiver unit. In the alignment unit, the pulse widths of the light pulses registered at the receiver are determined as the alignment criterion. The light pulses registered at a receiver are fed to a low-pass filter and then evaluated using a trigger threshold.

[0015] In the light barrier arrangement according to the invention, the alignment unit is designed to determine the pulse widths of light pulses that are emitted by the transmitters and can be received by the associated receivers.

[0016] EP 2 584 703 A1 relates to a photoelectric switch comprising a transmitter according to a specific light projection pattern from a plurality of light projection patterns with mutually different projected light periods and projected light pulse widths to perform, with each applicable projected light period, a light projection of the applicable pulse width toward a detection area; a detector that detects light from the detection area to generate a detected light pulse; and a pulse width evaluation section that evaluates whether or not a pulse width of the detected light pulse generated by the detector is substantially identical to the specific projected light pulse width of the light projection pattern to determine, if substantially identical, that light detected by the detector is locally emitted light projected by the transmitter, characterized inthat the photoelectric switch further comprises an evaluation section arranged to, when a locally emitted light has been identified by the pulse width evaluation section, add a prescribed number to a count value, and, if there is no subsequent identification of a locally emitted light during an interval from the time of this evaluation until the projected light period of the specific light projection pattern has elapsed, subtract a prescribed value from the count value to evaluate, based on the count value, whether a detection object is present in a detection area.

[0017] EP 3 059 616 A1 relates to an optical sensor for detecting objects in a surveillance area and comprises at least one transmitter emitting light beams and at least one receiver receiving light beams. The transmitter and receiver are arranged such that, when the surveillance area is clear, the light beams from the transmitter strike the receiver unhindered, and when an object intervenes in the surveillance area, the light beams strike the object and do not reach the receiver, or only reach it incompletely. An evaluation unit is provided in which, depending on the received signals at the output of the receiver, a binary switching signal is generated. The switching states of the binary switching signal indicate whether or not an object is present in the surveillance area. Test means are provided by means of which the transmitter is operated such that it emits a test signal.If the monitoring area is free, the received test signal is converted into a digital output signal and this is compared with a digital target signal stored in the test equipment for error control of the optical sensor.

[0018] According to the invention, the pulse widths are used as an alignment criterion for aligning the transmitter unit relative to the receiver unit. If the alignment is inadequate, only a small portion of a light pulse reaches the associated receiver. The receiver, with its upstream components such as amplifiers, is then operated in the linear range rather than in saturation, resulting in a small pulse width for the received light pulses. The better the alignment of the transmitter unit relative to the receiver unit, the greater the amount of light pulses reaching the receiver. The greater this amount of light, the more the receiver is operated in saturation and the larger the pulse width. The pulse width thus provides a reliable measure of the alignment quality of the transmitter unit relative to the receiver unit.

[0019] The light barrier arrangement according to the invention can generally be formed by a single light barrier, a multiple arrangement of light barriers or even by a light curtain.

[0020] A key advantage of the invention is that the alignment unit can utilize components for determining the pulse widths of the light pulses emitted by the transmitter(s) of the light barrier array and registered by the receiver(s) of the receiver unit that can also be used for signal evaluation to generate object detection signals. This results in a particularly simple and cost-effective design of the alignment unit.

[0021] The light barrier arrangement generally has an evaluation unit in which an object detection signal is generated depending on received signals. The object detection signal is preferably embodied as a binary switching signal, the switching states of which indicate whether an object is located in the monitoring area or not. In the simplest case, the evaluation unit has a computer unit formed by a controller or the like. In the event that the light barrier arrangement is a safety sensor with a fail-safe design for use in safety technology, the evaluation unit can have a redundant design with two computer units that cyclically monitor each other.

[0022] The evaluation unit contains one or more time measuring units that can be used to measure the pulse width.

[0023] To do this, however, the received light pulses must first be digitized.

[0024] In principle, the light pulses registered at a receiver could be evaluated using a trigger threshold.

[0025] According to the invention, the light pulses registered at a receiver are fed to a low-pass filter and then evaluated with a trigger threshold.

[0026] The low-pass filter broadens and filters the light pulses, so that an even more meaningful alignment criterion can be obtained.

[0027] The trigger threshold generates binary signals that are fed to a timing unit to determine pulse widths.

[0028] In the generated binary signal sequences, the signal state above the trigger threshold corresponds to an existing light pulse.

[0029] According to a further embodiment, the light pulses registered at a receiver are fed to an analog-to-digital converter.

[0030] In this case, the signals digitized in the analog-to-digital converter are fed to a timing unit to determine pulse widths.

[0031] The analog light pulse is thus converted into a digitized signal with a number of bits corresponding to the resolution of the analog-to-digital converter.

[0032] The components for generating the digitized signal sequences from the analog ones can advantageously be part of the evaluation unit.

[0033] It is particularly advantageous to determine an alignment quality for one or more receivers in the alignment unit based on the alignment criterion.

[0034] The alignment quality is higher the larger the pulse widths registered at the receiver(s).

[0035] According to an advantageous embodiment, display means for displaying the alignment quality are provided on the receiver unit.

[0036] The determined alignment quality is thus visualized on the receiver unit so that a user can use this display to align the receiver unit relative to the transmitter unit.

[0037] Advantageously, the display means comprise at least one optical display element.

[0038] In particular, the display element emits flashing sequences of visible optical pulses.

[0039] In the simplest case, the display element can be a light-emitting diode that emits visible light.

[0040] Advantageously, the alignment quality is encoded in the frequency, the pulse / pause ratio, the number of pulses in predetermined pulse groups, the pulse durations or the pauses between pulses that encode the visible light pulses emitted by the display element.

[0041] Based on the variation in the respective parameter, the user can precisely determine how well the transmitter unit and the receiver unit are aligned. If the user continuously changes the relative position of the transmitter unit and the receiver unit, the parameter of the emitted light from the display element also changes, allowing the user to precisely determine whether the change in position improves or worsens the alignment of the receiver unit relative to the transmitter unit.

[0042] In the event that the light barrier arrangement has a plurality of transmitters and receivers, wherein the light barrier arrangement can then be formed in particular by a light curtain, it is particularly advantageous if the display means have a plurality of display elements, wherein the display elements display the alignment quality of different receivers.

[0043] In particular, the display element is spatially assigned to the receiver(s) whose alignment quality it displays.

[0044] This spatially resolved display also allows tilting or twisting of the transmitter unit and the receiver unit to be detected and displayed, thus enabling further improved adjustment.

[0045] In particular, in the case of a light barrier arrangement designed as a light curtain, the transmitters and the receivers assigned to them form transmitter-receiver pairs which are cyclically activated one after the other, with the transmitter-receiver synchronization taking place in a known manner via the light pulses on an optical path.

[0046] A sliding chain is provided for individual activation of the receivers in the evaluation unit.

[0047] This sliding chain is also used particularly advantageously to control the display elements, resulting in a particularly simple circuit design.

[0048] Advantageously, each display element is assigned a display memory element which can be controlled with the sliding chain.

[0049] Flashing sequences of a display element are specified by information stored in the associated display memory element or via separate supply lines.

[0050] According to an alternative variant of the invention, the light barrier arrangement comprises a transmitter unit having an array of transmitters emitting light pulses, a receiver unit having an array of receivers, and an alignment unit for aligning the transmitter unit and receiver unit. In the alignment unit, the number of receivers receiving light pulses from their assigned transmitters is evaluated as the alignment criterion.

[0051] The invention is explained below with reference to the drawings. They show: Figure 1: Embodiment of the inventive light barrier arrangement in the form of a light curtain. Figure 2: Circuit arrangement of an alignment unit for the light curtain according to Figure 1 . Figure 3: Circuit arrangement for the arrangement of receivers and display elements for the light curtain according to Figure 1. Figure 4a, 4b: Different variants of the arrangement of display elements on a receiver unit of the light curtain according to Figure 1 . Figure 5a, 5b: First example of flashing sequences of a display element according to the Figure 3 , 4a, 4b . Figure 6a, 6b, 6c: Second example of flashing sequences of a display element according to the Figure 3 , 4a, 4b . Figure 7a - 7f: Third example of flashing sequences of a display element according to the Figure 3 , 4a, 4b . Figure 8a - 8e: Fourth example of flashing sequences of a display element according to the Figure 3 , 4a, 4b .

[0052] Figure 1 shows schematically an embodiment of the light barrier arrangement according to the invention in the form of a light curtain 1.

[0053] The light curtain 1 is used for object detection in a surveillance area. The light curtain 1 has a transmitter unit 2 with a housing in which a series arrangement of transmitters 4 emitting transmitted light beams 3 is provided. The transmitters 4, which are formed by light-emitting diodes or the like, emit transmitted 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.

[0054] The light curtain 1 further comprises a receiver unit 6, in whose housing a series arrangement of receivers 7 in the form of photodiodes or the like as well as an evaluation unit 8 are integrated.

[0055] 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 transmitted 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.

[0056] The transmitter-receiver pairs are activated cyclically, one after the other, via optical synchronization in a conventional manner. In this case, eight transmitter-receiver pairs are provided. Of course, a light curtain 1 can also have a different number of transmitter-receiver pairs.

[0057] Objects 9 in the surveillance area are detected by interrupting the beam path of the transmitted light beams 3 of at least one transmitter-receiver pair, as shown in Figure 1 shown.

[0058] In the evaluation unit 8, an object detection signal is generated based on the received signals, which is then transmitted to an external unit via an output. In this case, the object detection signal is generated as a binary switching signal, whose switching states indicate whether an object 9 is located within the monitoring area or not.

[0059] Figure 2 shows a computer unit in the form of a controller 10, as a component of the evaluation unit 8 of the light curtain 1. The controller 10 has a CPU 11, which controls the individual components of the controller 10. The controller 10 is a component of an alignment unit, which serves to align the transmitter unit 2 relative to the receiver unit 6.

[0060] According to the invention, the pulse widths of the light pulses 3a registered in the receivers 7 are determined in the alignment unit as an alignment criterion for the alignment.

[0061] The Figure 2shows an amplifier 12 in which a light pulse 3a registered at a receiver 7 is amplified. Generally, an amplifier 12 can be assigned to each receiver 7. Alternatively, an amplifier 12 is provided to which the received signals from all receivers 7 are fed in multiplex mode.

[0062] The signal 17a, 17b present at the output of the amplifier 12 is fed directly to a first comparator 13 and, via a low-pass filter 14, to a second comparator 15. As shown in Figure 2 As shown schematically, the light pulse 3a` is broadened by the low-pass filtering.

[0063] A first analog-to-digital converter 16a provides an adjustable trigger threshold for the first comparator 13. A second analog-to-digital converter 16b sets an adjustable trigger threshold for the second comparator 15. Alternatively, fixed trigger thresholds can also be specified.

[0064] The trigger threshold generates a sequence of binary signals 17a, 17b from the analog light pulses 3a, 3a`. The "high" state of a binary signal 17a, 17b corresponds to the presence of a light pulse 3a, 3a`.

[0065] These signals 17a, 17b are fed to the controller 10 via a timer input 18a, 18b or a digital input. A time measurement unit is integrated into the controller 10, particularly in the CPU 11, which is used to measure the time intervals of the "high" states of the digital signals 17a, 17b and thus the pulse width of the light pulses 3a.

[0066] In this case, a two-channel pulse width determination is performed by evaluating the digital signals 17a, 17b of both comparators 13, 15 in the timing unit. Generally, it is also possible to evaluate only the signals 17a, 17b of one comparator 13, 15.

[0067] The pulse widths of the light pulses 3a from the receivers 7 are evaluated as an alignment criterion in the alignment unit. The alignment quality is determined from the pulse widths, which increases with the larger the pulse widths.

[0068] In principle, only the light pulses 3a of one receiver 7 or a subset of the receivers 7 can be evaluated. In this case, the pulse widths are determined for all receivers 7 to determine the alignment quality.

[0069] The determined alignment quality is displayed via display elements 19a-19f. The display elements 19a-19f form indicators that emit visible light. In the simplest case, the display elements 19a-19f are formed by light-emitting diodes that emit visible light.

[0070] Figure 3 shows the control of the receiver 7 and the display elements 19a, 19b, 19c via the controller 10. In the present case, three display elements 19a, 19b, 19c are provided.

[0071] To control the eight receivers 7, a shift chain 20 with eight shift chain elements 20a - 20h, formed, for example, by flip-flops, is provided. Controlled by the controller 10, a bit value, such as a "1," is shifted through the shift chain elements 20a - 20h, thereby activating the receivers 7 one after the other.

[0072] This shift chain 20 is also used to control the display elements 19a, 19b, 19c. Each display element 19a, 19b, 19c is assigned a display memory element 21a, 21b, 21c, which is formed by a flip-flop. Control and addressing are performed via control lines 22, 23, 24 via the controller 10 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.

[0073] In addition, information is stored in the display memory elements 21a, 21b, 21c as to how, upon activation of the respective display memory element 21a, 21b, 21c, the associated display element 19a, 19b, 19c emits visible light with a specific flashing sequence, wherein the respective flashing sequence signals the current alignment quality.

[0074] In an alternative embodiment, the information change of the display elements 19a, 19b, 19c can also be carried out via one of the control lines 22, 23, 24.

[0075] Figure 4a shows the arrangement of the display elements 19a - 19c on the front of the receiver unit 6 with the receivers 7 located behind a disc.

[0076] As can be seen from Figure 4a, the first display element 19a is assigned to the two upper receivers 7 and displays the current alignment quality determined in the alignment unit for these two receivers 7. Accordingly, the display element 19b, which is assigned to the middle receivers 7, displays the current alignment quality for these two receivers 7. Finally, the third display element 19c is assigned to the two lower receivers 7 and displays the alignment quality determined in the alignment unit for these two receivers.

[0077] In general, other arrangements of display elements 19a - 19f on the receiver unit 6 are also possible. Figure 4b an arrangement with display elements 19a - 19c for displaying the alignment quality of the receivers 7 in the upper area of ​​the light curtain 1 and an arrangement with display elements 19d - 19f for displaying the alignment quality of the receivers 7 in the lower area of ​​the light curtain 1.

[0078] The Figures 5a, 5bshow a first example of different flashing sequences of a display element 19a-19f. In this case, the pulse / pause ratio of visible display light pulses of the display element 19a-19f is varied to indicate different alignment qualities.

[0079] The Figures 6a, 6b, 6c show another example of different flashing sequences of a display element 19a - 19f for indicating different alignment qualities. Depending on the alignment quality, the display element 19a - 19f emits visible light in the form of pulse groups with different numbers of individual display light pulses. For example, the emission of pulse groups according to Figure 6a a low alignment quality, with the emission of pulse groups according to Figure 6b a medium alignment quality and with the emission of pulse groups according to Figure 6c a high alignment quality of display elements 19a - 19f can be displayed.

[0080] The Figures 7a - 7fshow another example of different flashing sequences of a display element 19a - 19f for indicating different alignment qualities. In this embodiment, not only the number of display light pulses within a pulse group is determined, as in the embodiment according to the Figures 6a - 6c but also changes their pulse / pause ratio. The display light pulses are used starting from Figure 7a to Figure 7f a continuously improving alignment quality is displayed.

[0081] The Figures 8a - 8e show another example of different flashing sequences of a display element 19a - 19f for indicating different alignment qualities. In this embodiment, the pulse repetition frequencies and pulse durations of the individual display light pulses are varied. Starting from Figure 8a to Figure 8e a continuously improved alignment quality is indicated by the display element 19a - 19f. List of reference symbols

[0082] (1)Light curtain (2)Transmitter unit (3)Transmitted light beam (3a, 3a`)Light pulse (4)Transmitter (5)Transmitter control (6)Receiver unit (7)Receiver (8)Evaluation unit (9)Object (10)Controller (11)CPU (12)Amplifier (13)Comparator, first (14)Low-pass filter (15)Comparator, second (16a)Analog-to-digital converter, first (16b)Analog-to-digital converter, second (17a, b)Signal (18a, b)Timer input (19a - 19f)Display element (20)Sliding chain (20a - 20h)Sliding chain element (21a, b, c)Display memory element (22)Control line (23)Control line (24)Control line

Claims

1. A light barrier device with a transmitter unit (2) having at least one transmitter (4) emitting light pulses (3a), with a receiver unit (6) having at least one receiver (7) and with an alignment unit for aligning the transmitter unit (2) and receiver unit (6), wherein the pulse widths of the light pulses (3a) registered at the receiver (7) are determined in the alignment unit as an alignment criterion, characterised in that the light pulses (3a) registered at a receiver (7) are fed to a low-pass filter (14) and then evaluated with a trigger threshold.

2. A light barrier device according to claim 1, characterised in that the number of receivers (7) which receive light pulses (3a) from the transmitters (4) assigned to them is evaluated as an alignment criterion in the alignment unit.

3. A light barrier device according to one of claims 1 or 2, characterised in that binary signals (17a, 17b) are generated with the trigger threshold, which are fed to a timing unit for determining pulse widths.

4. A light barrier device according to one of claims 1 to 3, characterised in that the light pulses (3a) registered at a receiver (7) are fed to an analogue-to-digital converter (16a, 16b).

5. A light barrier device according to claim 4, characterised in that the signals (17a, 17b) digitised by analogue-digital converters (16a, 16b) are fed to a timing unit for determining pulse widths.

6. A light barrier device according to one of claims 3 to 5, characterised in that the timing unit is integrated in a computer unit which is part of the alignment unit.

7. A light barrier device according to claim 6, characterised in that the computer unit is part of an evaluation unit (8) in which an object detection signal is generated as a function of received signals from the receiver or receivers (7).

8. A light barrier device according to one of claims 1 to 7, characterised in that an alignment quality for the one or more receivers (7) is determined in the alignment unit on the basis of the alignment criterion, and in that display means for displaying the alignment quality are provided on the receiver unit (6).

9. A light barrier device according to claim 8, characterised in that the display means comprise at least one optical display element (19a - 19f).

10. A light barrier device according to claim 9, characterised in that the display element (19a - 19f) emits flashing sequences of visible optical pulses, the alignment quality being coded in the frequency, the pulse / pause ratio, the number of pulses in predetermined pulse groups, the pulse durations or the pauses between pulses of the visible optical pulses.

11. A light barrier device according to one of claims 9 or 10, characterised in that the display means have a plurality of display elements (19a - 19f), the display elements (19a - 19f) being used to display the alignment quality of different receivers (7), the display element (19a - 19f) being spatially assigned to the receiver or receivers (7) whose alignment quality it displays.

12. A light barrier device according to claim 11, characterised in that the display elements (19a - 19f) are addressed and controlled by means of a sliding chain (20).

13. A light barrier device according to claim 12, characterised in that the activation of the receivers (7) is controlled by means of the sliding chain (20).

14. A light barrier device according to one of claims 12 or 13, characterised in that each display element (19a - 19f) is assigned a display memory element (21a, 21b, 21c) which can be actuated with the sliding chain (20), wherein flashing sequences of a display element (19a - 19f) are predetermined by information stored in the assigned display memory element (21a, 21b, 21c) or via separate supply lines.

15. A light barrier device according to one of claims 1 to 14, characterised in that it is designed as a light curtain (1) and / or that it is a safety sensor.