JPH06132802A - Multiple optical axis photoelectric switch - Google Patents

Abstract

PURPOSE:To detect the time of shielding over arbitrary two optical axes as a light shielding state. CONSTITUTION:A light projecting control circuit light projecting means 3 of a flood light 1 simultaneously applies a reference signal for synchronization to two LED (light projecting element) 7a and 7b and successively applies light projecting signals to LED 7a-7e at prescribed light projecting timing. The reference signal for synchronization sets the first cycle at a high level and sets the second cycle at a low level. A photodetector 2 detects the reference signal for synchronization with a photodetection control circuit 13 based on the photodetection signals of output time corresponding to a photodetection level from photodetection units (photodetectors) 8a and 8b, generates a photodetection timing signal for two cycles and inputs a photodetection signal corresponding to a light projecting signal for detection. Even when any one of photodetection units 8a and 8n is shielded, the photodetection timing signal can be generated, the photodetection signal can be inputted synchronously with light projecting timing, and over arbitrary two optical axes can be surely detected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-optical axis photoelectric switch for detecting an object which forms a plurality of optical axes by a plurality of pairs of light emitting elements and light receiving elements and shields the optical axes.

[0002]

2. Description of the Related Art A multi-optical axis photoelectric switch of this type is applied to a safety device of a press device or the like because it can detect the presence or absence of an object by setting a wide detection area. It is configured. That is, a plurality of light projecting elements are arranged at a predetermined interval, and a plurality of light receiving elements forming a pair with each of the plurality of light projecting elements are arranged so as to face each other. Configure the optical axis,
A light emission control circuit outputs a light emission signal to sequentially turn on a plurality of light emitting elements of the light emitter one by one. On the light receiver side, the light reception control circuit sequentially inputs only the light reception signal output from the light receiving element of the corresponding optical axis based on the light reception timing signal synchronized with the light projecting timing of the light projecting element, and the received light is received. The signal is compared to a predetermined detection level. Then, when the level of the light receiving signal is higher than the detection level, it is judged to be the light receiving state, and when it is lower, it is judged to be the light shielding state and a detection signal is output to detect that an object has entered the detection area. Is configured.

Therefore, when the press device is used as a safety device, if the operation of the press device is stopped based on the detection signal, for example, the operator mistakenly operates the device during operation. It is possible to improve the safety of the work because the hands are not caught.

In the case of the above, in order to generate the light reception timing signal in synchronization with the light projection timing on the projector side in the light reception control circuit, for example, the reference signal for synchronization is transmitted from the projector side using a specific optical axis. There is one that is configured to output as a signal, detect the synchronization reference signal on the light receiver side, and generate a light reception timing signal based on this synchronization reference signal, which allows synchronization between the emitter and the light receiver. Compared to the structure in which the signal line is provided to directly receive the synchronization signal, the synchronization signal line is not necessary, and there are advantages that restrictions on the installation conditions of the light transmitter and the light receiver are reduced.

[0005]

By the way, when the above-mentioned multi-optical axis photoelectric switch is used as a safety device for a press machine, the machine stops when an object obstructs the detection area during operation of the press machine. For example, when processing a long iron plate whose end reaches the detection area, one optical axis is blocked by the thickness of the iron plate, so it is unavoidable to stop the multi-optical axis photoelectric switch. However, in that case, there was a problem that safety in work could not be ensured.

Therefore, in order to solve such a problem,
For example, in the one disclosed in Japanese Utility Model Application Laid-Open No. 57-136600, when two or more optical axes are shielded in the detection area of the multi-optical axis photoelectric switch, this is detected as a shielded state and pressed. There is provided a device which outputs a detection signal so as to stop the device. As a result, when a long workpiece is handled, even if the workpiece shields one optical axis of the detection area, it is not detected as a light-shielded state, and the operator's hand or the like falls within the detection area. The detection signal comes to be output only when the light enters and is shielded from two or more optical axes. Therefore, even in this case, work safety can be ensured.

However, in the conventional multi-optical axis photoelectric switch as described above, in the case of a structure in which the synchronizing reference line is not used and the synchronizing reference signal is sent as an optical signal from a specific optical axis, , If the specific optical axis is shielded, the reference signal for synchronization cannot be obtained on the light receiver side.
The light reception timing signal cannot be generated. As a result,
Even if only one optical axis is shielded, it is erroneously determined that the two optical axes are shielded. Therefore, when pressing a long workpiece as described above, the work is performed in a state where the particular optical axis for outputting the reference signal for synchronization is arranged so as not to be blocked by the workpiece. There is a need.

That is, in the conventional structure, although the detection signal is output by shielding the two optical axes, the condition for the two optical axis shielding detection is not satisfied for the specific optical axis.
As a condition of use, there is a restriction that a specific optical axis should be avoided to be used, and there is a problem that usability becomes poor for the user.

The present invention has been made in view of the above circumstances, and an object thereof is to detect when two or more arbitrary optical axes are simultaneously shielded as a shielded state, thereby restricting the use conditions. It is an object of the present invention to provide a multi-optical axis photoelectric switch that is not affected and is therefore easy to use.

[0010]

According to the present invention, a plurality of light projecting elements, a plurality of light receiving elements which are paired with each of the plurality of light projecting elements and constitute a plurality of optical axes, and the plurality of light projecting elements are provided. Among the elements, two or more predetermined light projecting elements are provided with the synchronization reference signal, and then each light projecting element is sequentially provided with a light projecting signal at a predetermined light projecting timing. The light is received by at least one light receiving element of the light emitting control means for giving a light emitting signal to perform one cycle of the light emitting operation, and the light receiving element paired with the two or more predetermined light emitting elements. A light receiving timing signal of each of the light receiving elements synchronized with the light emitting timing is set based on the synchronizing reference signal, and the light receiving signals of the plurality of light receiving elements are sequentially output based on the light receiving timing signal. Enter the duplicate Having the features of at two or more optical axis of the optical axis is constituted by a detecting means for outputting a detection signal when simultaneously exhibiting a light-shielding state.

[0011]

According to the multi-optical axis photoelectric switch of the present invention, the light projecting control means applies the synchronization reference signal to two or more light projecting elements of the plurality of light projecting elements and then sequentially determines the respective light projecting elements. Since the light emitting signal is given at the timing of, or the synchronizing reference signal is also given as a part of the light emitting signal,
An optical signal corresponding to the synchronization reference signal is output from the above light projecting element. On the other hand, the detection means receives and detects the optical signal corresponding to the synchronization reference signal by the corresponding light receiving element.

When the synchronizing reference signal is given from at least one light receiving element, the detecting means generates a light receiving timing signal synchronized with the light projecting timing of the plurality of light projecting elements based on the synchronizing reference signal. The light receiving signals of the light receiving elements corresponding to the light projecting elements are sequentially input based on the light receiving timing signal. Then, the detecting means detects the optical signal from each light projecting element corresponding to each light receiving element, and when no light receiving state signal is obtained from two or more light receiving elements, two or more optical axes are in the light blocking state at the same time. Then, the detection signal is output.

In this case, even if one of the optical axes corresponding to the projecting element to which the synchronizing reference signal is applied is shielded, the detecting means detects the synchronization detected from the other unshielded optical axes. Since the light reception timing signal can be generated by the use reference signal, the above-described detection operation can be reliably performed.

Further, when the optical axis to which the synchronizing reference signal is given is set to two optical axes and the two optical axes are shielded at the same time, the synchronizing reference signal cannot be detected by the detecting means. However, at this time, it is possible to detect the light blocking state of the two optical axes by not detecting the reference signal for synchronization.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to an area sensor used in a safety device of a press machine will be described below with reference to the drawings. That is, FIG. 1 shows an electrical block configuration, and the projector 1 and the photoreceiver 2 constituting this area sensor are electrically separated from each other. Each configuration will be described below.

First, in the projector 1, the projection control circuit 3 as a projection control means is a microcomputer, RO.
It is composed of M, RAM, etc., and a projection control program is stored in the ROM in advance. In the light emission control circuit 3, the output terminals A to E are connected to the control input terminals of the switch circuits 4a to 4e, and the output terminals F and G are connected to the respective input terminals of the voltage generating circuit 5.

The voltage generation circuit 5 outputs the synchronization reference signal and the detection light projection signal as voltage signals based on the signal supplied from the light projection control circuit 3, and its output terminal is the above-mentioned five switches. It is connected to each input terminal of the circuits 4a to 4e. The switch circuits 4a to 4e
The respective output terminals of are connected to LEDs (light emitting diodes) 7a to 7e as a plurality of light projecting elements via drive circuits 6a to 6e, respectively.

Next, the structure of the light receiving section 2 will be described. Five light receiving units 8a to 8 as a plurality of light receiving elements
e is provided so as to form five optical axes corresponding to the LEDs 7a to 7e, and as shown in FIG. 2, the light receiving element section 9, the amplification circuit section 10, the integration circuit section 11, and the comparison circuit section. It is formed as a one-chip element in which 12 is integrated.

Then, the light receiving units 8a to 8e
In FIG. 1, the light receiving element section 9 is composed of a photodiode or the like, and when receiving the pulsed light, converts the pulsed light into an electric signal and supplies the electric signal to the integration circuit section 11 via the amplification circuit section 10.
The integration circuit section 11 integrates the electric signal given from the amplification circuit section 12 and gives an analog signal as the integrated value to the comparison circuit section 13. The comparison circuit section 12 compares the level of the integrated value given as an analog signal from the integration circuit section 11 with a preset reference value, and in the state where the integrated value is larger than the reference value, the received light signal of the “H” level. Is output.

Therefore, the light receiving units 8a to 8e
When the amount of received pulsed light reaches a certain level,
The "H" level light receiving signal is output for a time proportional to the amount of received light. In the light receiving units 8a to 8e, when the amount of pulsed light entering the light receiving element section 9 is too strong, the electric signal input to the amplification circuit section 10 becomes excessive and may not be amplified and saturated. In this case, no signal is given to the integration circuit unit 11, and as a result, the light reception signal may be at the “L” level.

The light receiving control circuit 13 as the detecting means is composed of a microcomputer, ROM, RAM, etc., and the light receiving control program is stored in advance in the ROM. In the light receiving control circuit 13, the input terminals H to L are connected to the output terminals of the light receiving units 8a to 8e. Further, the output terminals M to O of the light receiving control circuit 13 are connected to the input terminals of the operation indicator lamp 14, the stable operation indicator lamp 15 and the output circuit 16, respectively.

The operation indicator lamp 14 lights up when it receives a display signal indicating the detected state of an object, and the stable operation indicator lamp 15 lights up when it receives a display signal indicating the stable operation state. Also,
The output circuit 16 provides an output to the output terminal Z when receiving the object detection signal.

Next, referring to FIGS. 3 to 5, the operation of the present embodiment will be described by dividing it into two operations, (1) light projecting operation, (2) light receiving operation and discriminating operation. 3 and 4 are time charts showing the signal output states of the respective parts of the projector 1 in correspondence with the first cycle and the second cycle of the projecting operation.

(1) Projection Operation First, in the projector 1, the projection control circuit 3 outputs the output terminal F.
And G outputs a binarized digital signal of "H" and "L" levels at a predetermined timing. As a result, in the voltage generating circuit 5, the voltage signal SV (see (f) in FIGS. 3 and 4) that changes in three stages according to the combination of the digital signals is input to each of the input terminals of the switch circuits 4a to 4e. To give to.

In this case, the voltage signal SV always has a low level voltage value, and becomes a high level voltage value at the timing corresponding to the synchronization reference signal in the first cycle (see FIG. 3).
(See (f)) At the timing corresponding to the synchronization reference signal in the second cycle, the voltage value remains at the low level (see FIG. 4).
(See (f)), and at the output timing of the detection light projection signal corresponding to each optical axis, a signal having a voltage value that gradually increases in three steps from low level to medium level to high level is set. ing.

On the other hand, the light emission control circuit 3 has a light emission timing corresponding to each optical axis from the output terminals A to E and has a short repetition period as shown in FIGS. 3 and 4A to 4E. The pulse signals SA to SE composed of a pulse train are output to turn on / off the switch circuits 4a to 4e. As a result, the drive signals 6a to 6e are supplied to the light emitting signals PA as shown in FIGS. 3 and 4 (g) to (k).
Or PE will be given.

That is, each switch circuit 4a to 4e
In, the voltage of the voltage signal SV when turned on by the pulse signals SA to SE is output to each of the drive circuits 6a to 6e as a light projecting signal. In this case, the pulse signals SA and SB include pulse train (burst wave) signals that match the output timing of the synchronization reference signal, and therefore the light projection signals PA and P are included.
Each of B is in a state of including the synchronization reference signals S1 and S2 in addition to the detection light projection signal. And
The output of the synchronization reference signal S1 in the first cycle becomes high level, and the output of the synchronization reference signal S2 in the second cycle becomes low level. Further, the detection light projection signals sequentially output corresponding to the respective optical axes are pulse train (burst wave) signals that sequentially rise in three steps. Note that the synchronization reference signal S1
And S2 are set to a time longer than the output time of the detection light projection signal.

The LEDs 7a to 7e are supplied with drive currents from the drive circuits 6a to 6e, respectively, and the amount of light emitted according to the level of the light emitting pulse signals PA to PE in one light emitting operation. , Will output pulsed light. In this case, LEDs 7a and 7b
In this case, after the pulsed light corresponding to the synchronization reference signal S1 is simultaneously projected, one projection operation is performed after a predetermined time. Further, the LEDs 7a to 7e carry out the light projecting operation of the second cycle after the light projecting operation of the first cycle is completed. Hereinafter, in the light projecting operation of the third cycle and thereafter, the above-mentioned light projecting operation of the second cycle is carried out. Will be repeated.

(2) Light Receiving Operation and Discriminating Operation Now, in response to the light projecting operation as described above, the light receiving section 2 performs the light receiving operation corresponding to each optical axis as follows. Be seen. That is, first, the light receiving unit 8a
And 8b, when receiving the pulsed light corresponding to the synchronization reference signals S1 and S2 from the LEDs 7a and 7b, respectively, "H" only for a time corresponding to the received amount of the pulsed light.
The light receiving signal of the level is output.

The light receiving control circuit 13 receives the light receiving signals given from the light receiving units 8a and 8b, detects the light receiving signals when the duration is within a predetermined judgment time, and outputs a synchronization detection signal, Based on this, the light reception timing signal synchronized with the light emission signals PA or PE is set to 2
Generate for cycles.

The light receiving signals corresponding to the synchronizing reference signal S1 or S2 from the light receiving units 8a and 8b are simultaneously input to the light receiving control circuit 13, and at this time, the rising and falling timings between the two. When there is a slight deviation, the light receiving control circuit 13 determines the time from the timing of the earlier rising to the timing of the later falling. In other words, the light receiving control circuit 13 accepts the time when either of the light receiving signals of both is at the "H" level as the output time of the light receiving signal of the "H" level. Therefore, either the optical axis of the light receiving unit 8a or 8b is blocked and the light receiving control circuit 13 is blocked.
When the "H" level received light signal is input from only one of them, the time from the rise to the fall is accepted as the output time of the received light signal.

Further, when the light receiving control circuit 13 detects the synchronizing reference signal, even if it generates the light receiving timing signal for two cycles based on the synchronizing reference signal detected in the immediately preceding cycle, it receives this signal. It is arranged to cancel and newly generate a light reception timing signal for two cycles.

When the light-reception control circuit 13 generates a light-reception timing signal synchronized with the light-projection timing by thus detecting the synchronization reference signal, the light-reception units 8a to 8e output the light-reception timing signal based on the light-reception timing signal. The light receiving signals are sequentially received. That is, the light receiving control circuit 13 can input the light receiving signals output by the light receiving units 8a to 8e of the corresponding optical axes in synchronization with the pulsed light output from the LEDs 7a to 7e. is there.

Now, in each of the light receiving units 8a to 8e, the corresponding LEDs 7a to 7e are intermittently interrupted in a short cycle as shown in FIG. Since the rising pulsed light is given, an analog signal having an integrated value as shown in FIG. 7B is obtained according to the amount of received light. As a result, the light receiving units 8a to 8e output the light receiving signals having the output times as shown in any of (c) to (f) of FIG.

In this case, in the light receiving units 8a to 8e, if the integrating circuit section 11 obtains, for example, an analog signal as shown by the solid line in FIG. Since the first value of the three levels has already exceeded the value TH, the light receiving control circuit 13 receives a light receiving signal having an output time as shown in FIG. Further, when an analog signal as shown by a broken line in FIG. 3B is obtained by the integration circuit unit 11, the value of the highest level at the end of the three levels of the analog signal becomes the comparison reference value TH. Since it reaches, the light receiving control circuit 13 receives a light receiving signal having an output time as shown in FIG.

Further, when there is an object that blocks the optical axis, the light receiving signals are not output from the light receiving units 8a to 8e corresponding to the optical axis, so that FIG.
As shown in, the light reception control circuit 13 is prevented from receiving the “H” level light reception signal corresponding to the synchronization timing, and the light blocking of the object can be detected.

The light-reception control circuit 13 determines the output time by the light-reception control program according to the input states of such various light-reception signals. That is, when the number of light receiving signals input from the five light receiving units 8a to 8e is 3 or less in one cycle of the light projecting operation, the light receiving control circuit 13 determines that two or more optical axes in the detection area are the object. Assuming that the operation indicator lamp 14 is in a light-shielded state, a display output is given to the operation indicator lamp 14 to light it, and an object detection signal is given to the output circuit 16 to give an output signal to the output terminal Z.

When the two optical axes corresponding to the light receiving units 8a and 8b are shielded, the light receiving control circuit 13
However, the reference signal for synchronization thereafter cannot be detected, but this makes it possible to detect the light blocking state of the two optical axes in the detection area. Further, when the number of light-receiving signals input from the light-receiving units 8a to 8e is 4 or more, the light-receiving control circuit 13 determines that the two-optical axis is not in the light-shielded state, turns off the operation indicator lamp 14, and outputs the output circuit 16 No object detection signal is output.

Further, the light receiving control circuit 13 receives light receiving signals from all of the light receiving units 8a to 8e, and the input timings of all the light receiving signals are within a predetermined time from the rise of the light receiving timing signal, that is, When the amount of received light is sufficient and the rise time of the received light signal is short, the stable operation indicator lamp 15 is given a display signal to be turned on.

When the light emitter 1 and the light receiver 2 are placed too close to each other or too far from each other, the amount of light received by the light receiver 2 of the pulsed light output from the light emitter 1 is too large. It may become insufficient or insufficient. In such a case, the light receiving unit 8
There is a case where the light receiving signal corresponding to the synchronization reference signal is not output because the level of the electric signal output when receiving the pulsed light corresponding to the synchronization reference signal in a or 8b is too high or too low. is there.

This is because, for example, in the light receiving unit 8a or 8b, when a high level electric signal is input from the light receiving element section 9 to the amplifier circuit section 10, the amplifier circuit section 10 becomes saturated and the output becomes zero. In such a case, as a result, the amount of received light is too high, but on the contrary, the level of the received light signal at the “H” level is not output from the comparison circuit unit 12. On the other hand, when the amount of light received by the light receiving unit 8a or 8b is insufficient, the output time of the light receiving signal does not reach the time required for the determination of the synchronization reference signal.

In response to such a situation, the synchronization reference signal in this embodiment is set to different levels in the first cycle and the second cycle, so that in the light receiving unit 8a or 8b of the light receiver 2, If the pulsed light of the level of at least one of the cycles can be detected as the light receiving signal of the synchronization reference signal, the light receiving timing for two cycles until the next synchronization reference signal of that level is detected. You can get a signal.

That is, the synchronization reference signal S in the first cycle
The distance between the light projector 1 and the light receiver 2 can be set so that the light reception control circuit 13 can detect either the synchronization reference signal S2 in the first or second cycle. As a result, the range of the disposition distance between the light projector 1 and the light receiver 2 is widened.

As described above, in the present embodiment, the light emitting control circuit 3 gives a reference signal for synchronization to the two LEDs 7a and 7b, and the light receiving control circuit 13 causes the light receiving unit 8a or 8b of the corresponding optical axis. The reference signal for synchronization is determined based on the received light signal. This allows
When detecting the light blocking state of the two optical axes, even if one of the optical axes of the light receiving units 8a or 8b for detecting the reference signal for synchronization is shielded, the reference signal for synchronization is obtained from the other light receiving signal. It becomes possible to detect and generate the light reception timing signal. Therefore, it is possible to surely detect the light blocking state of two or more arbitrary optical axes.

Further, in the present embodiment, the light emission control circuit 3 sets the light emission amount of the synchronizing reference signal to a different level by increasing the first cycle and decreasing the second cycle, and at the same time, the light receiving control circuit is provided. When the reference signal for synchronization is detected by 13, the light reception timing signal for two cycles is generated. As a result, the projector 1 and the receiver 2
Even if the light receiving unit 8a and 8b cannot receive a light receiving signal because the light receiving unit 8a and the light receiving unit 8b have an excessively large amount of light, the distance between the two synchronizing reference signals S1 or If either one of S2 can be detected, a light receiving timing signal synchronized with the light emitting operation for two cycles can be obtained, so that the distance between the light emitting and light receiving devices that can reliably detect the reference signal for synchronization is in a wide range. You can set it.

Further, in this embodiment, since the pulsed light whose projection amount changes in three steps in one projection operation is used as the projection signal for detection, the same as in the case of detecting the reference signal for synchronization. Thus, the distance between the light-emitter and the light-receiver capable of detecting the light-shielded state can be set in a wide range from the close distance to the long distance.

In the above embodiment, the reference signal for synchronization is output from the LEDs 7a and 7b corresponding to the adjacent two optical axes, but the present invention is not limited to this, and for example, the LED 7a corresponding to the separated two optical axes. And 7e may be set to output. In this case, the optical axes that output the synchronization reference signals are almost never shielded at the same time, so even if the two optical axes including one synchronization optical axis are shielded, the synchronization reference Can generate a signal,
The light blocking state can be detected in a state in which the light projecting device 1 is surely synchronized with the light projecting device 1. This makes it possible to detect the light blocking state a plurality of times and output the object detection signal.

Further, in the above embodiment, the reference signals for synchronization are simultaneously output from the LEDs 7a and 7b, and the light receiving signals from the light receiving units 8a and 8b are synchronized in the time from the timing of early rising to the timing of late falling. Although the detection signal is detected, the detection signal is not limited to this.
For example, the output time of each light receiving signal may be individually determined and the light receiving timing signal may be generated at either one of the detection timings, or the synchronization reference signal may be output at different timings, and the light receiving unit may be output. The light reception timing signal may be generated with reference to one of the synchronization reference signals determined from the light reception signals output from 8a or 8b.

Furthermore, in the above embodiment, the synchronizing reference signal is output from the two LEDs 7a and 7b, but the present invention is not limited to this, and three or more synchronizing reference signals are output from different LEDs 7a to 7e. The structure does not matter.

In the above embodiment, the synchronizing reference signal is output at two different levels over two cycles, but the present invention is not limited to this, and for example, it may be set at three or more different levels. You may make it output over 3 cycles or more. In this case, in the light receiving control circuit 13, when the synchronization reference signal is detected,
It may be configured so as to generate a light reception timing signal of three cycles or more.

In addition, in the above-described embodiment, the detection light projecting signal is output as a pulse train signal of three different levels. However, the present invention is not limited to this. For example, a single-shot pulse signal is detected. Alternatively, the signals may be output as signals of different levels in a plurality of stages.

Further, in the above embodiment, the reference signal for synchronization and the light projecting signal for detection are separately output, but the invention is not limited to this. For example, pulsed light output from the projector 1 side is a single pulse. LED7a when light is used
Alternatively, the reference signal for synchronization and the light projecting signal for detection may be given as one signal. In this case, the time for one cycle of the light projecting operation can be shortened accordingly.

Further, in the above embodiment, the case where the light receiving units 8a to 8e which are made into one chip are used is described, but the present invention is not limited to this, and the light receiving element, the amplifying circuit, the integrating circuit, and the comparing circuit are separately provided. Also good.

[0054]

According to the multi-optical axis photoelectric switch of the present invention,
The light emission control means gives a synchronization reference signal to two or more predetermined light emitting elements, and the detection means detects the synchronization reference signal received by at least one light receiving element of the light receiving elements to receive light of the light receiving elements. Since the timing signal is generated and the detection signal is output when two or more optical axes out of the plurality of optical axes are in the light blocking state based on the light reception timing signal, the synchronization reference signal is output. Even if one of the optical axes of the optical element is shielded, it is possible to generate a light reception timing signal by detecting the reference signal for synchronization from another projecting element. Therefore, when two or more optical axes are shielded Therefore, it is possible to reliably output the detection signal, and it is possible to obtain the excellent effect that the detection condition is not restricted and the usability is improved.

[Brief description of drawings]

FIG. 1 is an electrical block diagram showing an embodiment of the present invention.

FIG. 2 is an electrical block configuration diagram of a light receiving unit.

FIG. 3 is a time chart of signals in the first cycle in each part of the projector.

FIG. 4 is a time chart of signals in the second cycle.

FIG. 5 is an operation explanatory view showing a signal output state according to a light receiving state in the light receiving unit.

[Explanation of symbols]

1 is a light emitter, 2 is a light receiver, 3 is a light emission control circuit (light emission control means), 4a to 4e are switch circuits, 5 is a voltage generation circuit, 7a to 7e are LEDs (light emitting elements), and 8a to 8e are A light receiving unit (light receiving element), 13 is a light receiving control circuit (detection means), 14 is an operation indicator lamp, 15 is a stable operation indicator lamp, and 16 is an output circuit.

Claims (1)

[Claims] 1. A plurality of light projecting elements, a plurality of light receiving elements which form a plurality of optical axes in pairs with each of the plurality of light projecting elements, and two or more predetermined ones of the plurality of light projecting elements. After the synchronization reference signal is applied to the light projecting element, each light projecting element is sequentially provided with a light projecting signal at a predetermined light projecting timing, or the synchronization reference signal is also provided as a part of the light projecting signal. The light emitting control means for performing the light emitting operation for one cycle, and the synchronizing reference signal received by at least one light receiving element of the light receiving elements paired with the two or more predetermined light emitting elements are detected. A light receiving timing signal of each light receiving element is set in synchronization with the light projecting timing based on a synchronization reference signal, and light receiving signals of the plurality of light receiving elements are sequentially input based on the light receiving timing signal, and the light receiving signals of the plurality of optical axes are input. 2 or more lights A multi-optical axis photoelectric switch comprising: a detection unit that outputs a detection signal when the axes simultaneously exhibit a light-shielded state.