JP3046400B2 - Multi-optical axis photoelectric switch - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention comprises a plurality of pairs of a light emitting element and a light receiving element, and activates a light receiving signal from the light receiving element of the pair in synchronization with the lighting of the light emitting element in the detection area. The present invention relates to a multi-optical axis photoelectric switch configured to detect a light blocking state in a detection area.

[0002]

2. Description of the Related Art This type of photoelectric switch can detect the presence or absence of an object in a wide detection area, and is used, for example, as a safety device for a press device. The schematic configuration is as follows. That is, a plurality of pairs of light emitting elements and light receiving elements are provided, and the light emitting elements are sequentially emitted one by one into the detection area in accordance with a signal from the control circuit. On the other hand, the light-receiving element group is connected to a selection circuit having a plurality of input terminals, and only one light-receiving element paired with the light-emitting light-emitting element of the light-receiving element group has an emission timing of the light-emitting element. Synchronized and activated by the selection circuit.

The light receiving signal passed from the light receiving element to the selection circuit is amplified by a light receiving amplifier, compared with a predetermined reference level by a comparing circuit, and when it is determined that the light receiving amount in any one of the light receiving elements has decreased. It is determined that an object has entered the optical axis of the light emitting element and the light receiving element in the detection area.

In this case, when one light emitting element emits light, only the light receiving signal from the light receiving element forming a pair is validated for the following reason. That is, the light emitted from the light projecting element is not always incident only on the light receiving element that is paired with the light emitting element, and may be incident on the light receiving element provided in the vicinity as light having relatively high intensity. Therefore, if the light receiving signals from all the light receiving elements are equally input to one comparing circuit, the light receiving state is determined in spite of the invasion of the object even though the optical axis is in the light shielding state, and the object is detected. This is because intrusion cannot be detected accurately.

[0005]

However, even when the detecting operation is performed in a state where the light emitting element and the light receiving element are synchronized as described above, accurate detection cannot be performed in the following cases. There are cases.

That is, for example, when an object enters an optical axis formed by a pair of a light emitting element and a light receiving element and is in a light blocking state, light from the light emitting element is applied to this light receiving element. Although it should be in a non-light-incident state by not entering, at this time, when external light such as light emitted from another sensor or sputter light or light from a lighting device enters the light-receiving element as external disturbance light, When the light receiving state is determined, the light blocking state may not be detected.

[0007] The detection of the light receiving state in the light-shielded state as described above is a disadvantage in that when used as a safety device, it operates on a dangerous side.

The present invention has been made in view of the above circumstances, and an object of the present invention is to detect a light incident state due to disturbance light to quickly eliminate the adverse effect of the disturbance light. An object of the present invention is to provide a multi-optical axis photoelectric switch that can always accurately detect a state.

[0009]

SUMMARY OF THE INVENTION A multi-optical axis photoelectric switch according to the present invention comprises a plurality of light emitting elements which are sequentially turned on at a predetermined timing so as to irradiate light toward a detection area; A plurality of light-receiving elements provided so as to form a pair with the element and receiving light from the detection area, and light-receiving signals from the respective light-receiving elements being enabled in synchronization with the lighting timing of the light-emitting element forming the pair; Control means for determining the light blocking state in the detection area based on the light receiving signal from the light receiving element, and light receiving signals from the plurality of light receiving elements at non-light emitting timings of the plurality of light emitting elements. An inspection means for sequentially validating and detecting a state of input of disturbance light into the detection area is provided.

[0010]

According to the multi-optical axis photoelectric switch of the present invention, the control means detects the light blocking state in the detection area by sequentially operating each pair of the plurality of light emitting elements and light receiving elements. It is that by sequentially activate light reception signals from a plurality of receiving <br/> optical element in a non-light emitting timing of the plurality of light emitting devices,
It is detected whether there is a light incident state due to a light source other than the light projecting element, that is, disturbance light. As a result, it is possible to quickly eliminate the occurrence of erroneous detection or the like due to disturbance light in the detection operation of the light-shielded state by the control means, and thus to perform accurate detection.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to an eight-optical-axis area sensor used for a safety device of a press device will be described below with reference to the drawings.

FIG. 1 schematically shows an electric configuration. This area sensor is composed of a light projector 1 and a light receiver 2 which are electrically separated.

First, in the light projector 1, eight LEDs (light emitting diodes) 3 a to 3 h as a plurality of light emitting elements are connected to a microcomputer 5 via a light emitting circuit 4. The DC power supply circuit 6 is connected to the microcomputer 5 and to the light emitting circuit 4 via the current detection circuit 7, so that power is supplied at a predetermined DC voltage. The current detection circuit 7 is composed of, for example, a current detection resistor that obtains a terminal voltage in proportion to the flowing current, and two comparators to which the terminal voltage is applied, and when the terminal voltage is within a predetermined range. One comparator inputs an "H" level signal to the microcomputer 5 and the other comparator inputs an "L" level signal to the microcomputer 5.

The microcomputer 5 supplies a light emitting signal to the LEDs 3a to 3h via the light emitting circuit 4 as described later. The LEDs 3a to 3h are respectively provided with eight optical axes toward the detection area 8. Light for detection is sequentially projected.

A display circuit 9 for displaying the operation state of the projector 1 is connected to the microcomputer 5. The display circuit 9 is provided with a display LED 9a (see FIG. 2), and a display signal is supplied from the microcomputer 5 according to the operation state of the light projector 1 as described later.

The light emitting circuit 4 described above is configured as shown in FIG. That is, the driving circuits 10a to 10h for driving the respective LEDs 3a to 3h for lighting are connected. The driving circuits 10a to 10h are connected to output terminals of AND circuits 11a to 11h, respectively. One input terminal of each of the AND circuits 11a to 11h is connected to the output terminal Q of the shift register 12a to 12h, respectively.
0 to Q7, and AND circuits 11a to 11a
The other input terminal 1h is connected to the output terminal A of the microcomputer 5.

Data input terminal D of shift register 12a
0 is connected to the output terminal B of the microcomputer 5,
The output terminal Q0 is connected to the data input terminal D1 of the shift register 12b.
Output terminals and data input terminals are sequentially connected. The output terminal Q of the shift register 12h
7 is connected to the microcomputer 5. Also,
The clock input terminals CK of the shift registers 12a to 12h are connected to the output terminal C of the microcomputer 5.

The light emitting circuit 4 is divided into a main circuit 4a for driving the LEDs 3a to 3d to emit light and a sub-circuit 4b for driving the LEDs 3e to 3h to emit light. Two circuit parts 4 for the optical axis
a and 4b are used in a serially connected state. Further, a similar sub-circuit unit can be serially connected to the subsequent stage of the sub-circuit unit 4b.

Next, in the light receiver 2, eight PDs (photodiodes) 13a to 13h as a plurality of light receiving elements are provided.
Are connected to a microcomputer 15 via a light receiving circuit 14. This microcomputer 15 has both functions as a control unit and an inspection unit. The DC power supply circuit 16 is connected to the microcomputer 15 and supplies power at a predetermined DC voltage. The PDs 13a to 13h are arranged toward the detection area 8 so as to form a pair with the LEDs 3a to 3h.

The output line of the light receiving circuit 14 is connected to the microcomputer 15 via a line check circuit 17 and to the microcomputer 15 via a detection circuit 18 which is a judgment means. The microcomputer 15 is connected to an output circuit 19 for outputting a judgment result and a display circuit 20 for displaying the judgment result.

As will be described later, the light from the detection area 8 received by the photodiodes 13a to 13h is converted into an electrical output signal and input to the microcomputer 15 via the line check circuit 17 and the detection circuit 18, The state in the detection area 8 is determined.

Now, the above-mentioned light receiver 2 is configured in detail as shown in FIG. That is, each of PDs 13a to 13h
A conversion circuit 21a for converting a light receiving signal into an electric signal.
To 21h are connected. Each conversion circuit 21a to 2
1h is connected to the detection circuit 18 and the line check circuit 17 via analog switches 22a to 22h, respectively. The output terminals Q0 to Q7 of the shift registers 23a to 23h are connected to the gates of the analog switches 22a to 22h, respectively.

The line check circuit 17 provides the microcomputer 15 with an "H" level output based on the output voltage of the analog switches 22a to 22h in the on state and an "L" level output based on the off state output voltage. It has become.

Data input terminal D of shift register 23a
0 is connected to the output terminal a of the microcomputer 15, the output terminal Q0 is connected to the data input terminal D1 of the shift register 23b, and so on.
3c to 23h are serially connected. The output terminal Q7 of the shift register 23h is the microcomputer 1
5 is connected. The clock input terminals CK of the shift registers 23a to 23h are connected to the output terminal b of the microcomputer 15.

The light receiving circuit 14 includes PDs 13a to 13a.
d, a main circuit unit 14a for receiving a light receiving signal from
It is divided into a sub-circuit unit 14b for receiving light receiving signals from D13e to 13h. In this embodiment, two circuit units 14a and 14b for eight optical axes are used in a serially connected state. . Further, a similar sub-circuit unit can be serially connected to the subsequent stage of the sub-circuit unit 14b.

The detection circuit 18 is a comparison circuit 1 for detecting light shielding.
8a, a comparing circuit 18b for detecting a stable incident light, and a waveform shaping circuit 18c. A detection signal is given from the light receiving circuit 14, and the output is sent to the microcomputer 1
Give 5 Also, from the microcomputer 15,
A feedback signal for hysteresis is supplied to each of the circuits 18a to 18c.

When a light receiving signal exceeding a predetermined light incident detection level is applied, the light shielding detection comparing circuit 18a outputs an "H" level signal indicating the light incident state to the microcomputer 1.
5 is output. The stable light incident detection comparison circuit 18b is set to a stable light incident detection level higher than the above-described light incident detection level. When a light receiving signal exceeding this stable light incident detection level is given, the stable light incident state is set. Is supplied to the microcomputer 15. When a burst signal is given as a light receiving signal, the waveform shaping circuit 18c gives a synchronization detection signal to the microcomputer 15 as described later.

The output circuit 19 is composed of a detection output circuit 19a for detecting and outputting light-shielded light and an alarm output circuit 19b for notifying an unstable light incident state. An output is applied to a load (not shown) connected to the output terminal.

The display circuit 20 has three LEDs 20a, 2
For example, the LED 20a is red, the LED 20b is yellow, and the LED 20c is green. These LEDs 20a to 20c are turned on according to a display output signal from the microcomputer 15.
By operating in a mode such as lighting, extinguishing, or blinking, respectively, it is driven in various modes indicating a light receiving state as described later.

Next, the operation of the present embodiment will be described with reference to FIGS. 4 and 5 by dividing the operation into each operation in one cycle (for example, one cycle in 5 msec) shown below. That is,
(1) standby state, (2) synchronization signal detection, (3) disturbance light detection operation, (4) light-shielded state detection operation, (5) light emission state detection operation, and (6) light reception state detection operation is there.

The time chart of FIG. 4 shows the output signals from the respective components of the microcomputer 5 in the light projector 1 and the output states of the respective components of the light projector circuit 4. The time charts of the portions indicated by A to K in FIG. This corresponds to the output state. The time chart of FIG. 5 shows output signals from each part of the microcomputer 15 in the light receiver 2 and output states of each part of the light receiving circuit 14.
Through j. (1) Standby state First, in the projector 1, the microcomputer 5
A pulse signal is input to the data input terminal D0 of the shift register 12a (see FIG. 4B), and a clock signal is input to clock input terminals CK of the shift registers 12a to 12h (see FIG. 4C).

As a result, the output terminal Q0 of the shift register 12a goes high (see FIG. 4D).
One of the input terminals of the ND circuit 11a is in a state where an "H" level signal is applied. As a result, when an “H” level signal is applied to the other input terminal of the AND 11a,
The LED 3a is turned on by the drive circuit 10a.

On the other hand, in the photodetector 2, the microcomputer 15 inputs a pulse signal to the data input terminal D0 of the shift register 23a (see FIG. 5A), and also connects the pulse signal to the clock input terminals CK of the shift registers 23a to 23h. A clock signal is input (see FIG. 5B).

As a result, the output terminal Q0 of the shift register 23a becomes "H" level (see FIG. 5 (c)).
The analog switch 22a is turned on. As a result, the conversion circuit 21a enters a state in which the light receiving signal detected by the PD 13a can be output to the detection circuit 18.

As described above, the light emission from the LED 3a is set to a standby state in which the light can be detected by the PD 13a. (2) Synchronization signal detection The microcomputer 5 of the projector 1
A burst signal for synchronization is output to the other input terminals a to 11h (see FIG. 4A). By this, LED
3a is driven by the drive circuit 10a and projects light for synchronization detection toward the detection area 8.

On the other hand, in the light receiver 2, the light for synchronization detection projected on the detection area 8 by the LED 3a is transmitted to the PD1.
When received by 3a, the light receiving signal is input to the waveform shaping circuit 18c via the conversion circuit 21a and the analog switch 22a. When the level of the light receiving signal reaches a predetermined value, the waveform shaping circuit 18c inputs a synchronization detection signal to the microcomputer 15.

Thus, the microcomputer 15
Receives a synchronization detection signal, determines that the signal is a signal of a predetermined length, and outputs a control signal to the light receiving circuit 14 at a predetermined timing to perform a predetermined detection operation described below. become. (3) Operation for Detecting Disturbance Light In the projector 1, the microcomputer 5 maintains a state in which the microcomputer 5 outputs a burst signal and does not output a signal for a certain period of time. That is, an "L" level signal is applied to the other input terminals of the AND circuits 11a to 11h, and all the LEDs 3a to 3h are turned off.

On the other hand, during the above-mentioned fixed period in which the light projector 1 does not emit light, the light receiver 2 operates as follows in order to detect disturbance light. That is, the microcomputer 15 supplies seven continuous clock signals at short intervals to the clock output terminals CK of the shift registers 23a to 23h.

In the shift registers 23a to 23h, the state of the signal output at the "H" level is shifted from the output terminals Q0 to Q7 each time the clock signal is supplied (FIGS. 5C to 5J). reference). As a result, the analog switch 22a, which was in the conductive state, is sequentially shifted to the conductive state of the analog switches 22b to 22h, and the light receiving signals of the PDs 13a to 13h are sequentially applied to the detection circuit 18.

Now, since the light is not projected from the light projector 1, the light receiving signal should not be detected by the above-described operation.
That is, light from other light sources, that is, disturbance light is detected. When the disturbance light is detected in this manner, the microcomputer 15 sets the red LED 20
A flash signal is given to a, and an "H" level signal is output to the alarm output circuit 19b to notify the "disturbance light detection state".

The above-mentioned "disturbance light detection state" is notified when the detection frequency is low, that is, when the detection is performed in a short time and even once, and the "disturbance light detection state" is continued for, for example, 6 μsec or more. Alternatively, when the detection is continuously performed in three cycles, the microcomputer 15 outputs a detection signal to the detection output circuit 19a in addition to the above, assuming that the detection frequency is high. That is, the detection output is made to be in the same state as the light-shielded state due to the intrusion of the object, thereby acting on the safe side. The output state is locked and maintained until the power is turned off.

In this case, a time period of, for example, about 800 μsec is set as the fixed period for detecting the disturbance light. (4) Light-Detection State Detection Operation When the disturbance light detection operation is completed, in the projector 1, the microcomputer 5 sequentially outputs pulse signals to the other input terminals of the AND circuits 11a to 11h at predetermined intervals (FIG. At the same time, a clock signal is sequentially output to the shift registers 12a to 12h between the pulses of the pulse signal (see FIG. 4C). With this, first,
Since the shift register 12a is at the "H" level in the initial state (see FIG. 4D), the LED 3a is turned on during the period when the pulse signal is supplied to the AND circuit 11a.

On the other hand, in the photodetector 2, the microcomputer 15 outputs an "H" level signal to the data input terminal D0 of the shift register 23a, and outputs a "H" level signal to the clock input terminals CK of the shift registers 23a to 23h for a predetermined time interval. And outputs a pulse train.

As a result, an "H" level signal is output from the output terminal Q0 of the shift register 23a to turn on the analog switch 22a and to enable the detection signal of the PD 13a. Therefore, when the LED 3a is turned on,
If the optical axis is not blocked by the intrusion of the object, LED
The light emitted from 3a is detected by the PD 13a, and the microcomputer 15 outputs "H" to the microcomputer 15 via the light-shielding detection circuit 18a.
A signal indicating the light incident state of the level is output.

Further, when an object has intruded and is blocking light emission of the LED 3a, the microcomputer 15 stores that light shielding is detected once because no light receiving signal is output. If the detection of light-shielding is repeated two or more times, the microcomputer 15 determines that the state is "light-shielded", turns on the red LED 20a of the display circuit 20, and supplies an output signal to the detection output circuit 19a. ing.

Hereinafter, the LEDs 3b to 3h and the PD 13b
13h are sequentially operated to transmit and receive light of each optical axis. Then, the microcomputer 15 detects the presence or absence of the “light-shielded state” due to the intrusion of the object in the same manner as described above. (5) Operation for detecting light emitting state a. Shift Register Operation State Detection In the projector 1, the microcomputer 5 detects whether there is any abnormality in the operation states of the shift registers 12a to 12h based on the output signal from the output terminal Q7 of the shift register 12h.

That is, if the shift registers 12a to 12h are operating normally, the output terminal Q7 of the shift register 12h should output a signal as shown in FIG. The input pattern during normal operation is stored in the microcomputer 5 in advance, and when a signal from the shift register 12h does not match the input pattern, it is determined that a failure has occurred in any of the shift registers 12a to 12h. Judgment is made, and a flashing signal is output to the LED 9a of the display circuit 9 and all light emitting operations are stopped.

Thus, the shift registers 12a to 12a
If any one of 2h fails, it is possible to report occurrence of a malfunction such as the "H" level signal being kept output from the output terminal or the shift operation of the output signal not being performed. Further, all the light projecting operations are stopped, and a state similar to a light blocking state due to the intrusion of an object is made to work on the safe side. This state is locked and maintained until the power is turned off. b. As described above, the current supply to the LEDs 3a to 3h is performed via the current detection circuit 7, and if the detected voltage appearing in accordance with the supplied current is within a predetermined range, two comparators are used. Output detection signals of "H" level and "L" level, respectively. When the lighting operation is performed normally, the LEDs 3a to 3h are sequentially turned on one by one. The "H" level and "L" level signals should have been output from the comparator, respectively.

When the microcomputer 5 performs energization lighting for each of the LEDs 3a to 3h, the detection signal from the current detection circuit 7 becomes "H" level and "L".
If the level is normal, it is determined to be normal. Otherwise, it is determined to be "abnormal", a flashing signal is output to the LED 9a of the display circuit 9, and all light emitting operations are stopped.

As a result, the shift registers 12a to 12a
2h, AND circuits 11a to 11h or drive circuit 10a
A state in which one or more of the LEDs 3a to 3h are turned on at the same time due to a failure of any one of the LEDs 10a to 10h, or a state in which none of the LEDs 3a to 3h are turned off can be quickly detected and notified. Also,
All light emitting operations are stopped (when two or more light emitting elements are lit), and a state similar to a light-shielding state due to the intrusion of an object is made to work on the safe side. Then, the projection stop state is locked and maintained until the power is turned off. (6) Light-receiving state detection operation a. Light-receiving (light-receiving) level detection In the light-receiving device 2, light-receiving signals from the PDs 13a to 13h are also input to a stable light-receiving detection circuit 18b. As described above, the stable detection level of the stable light detection circuit 18b is set to a level higher than the detection level of the above-described light blocking detection circuit 18a.

When the received light signal is given, the stable light detection circuit 18b compares its level with the stable detection level,
When the level of the light receiving signals from D13a to D13h exceeds the stability detection level, the microcomputer 15 outputs a detection signal indicating "stable light input state" to the microcomputer 15. In addition, the microcomputer 15 responds to the request by all PD1s.
When a detection signal indicating a “stable light incident state” is obtained from 3a to 13h, a lighting signal is output to the green LED 20c of the display circuit 20 to notify the “stable light incident state”, and the stable light incident detection circuit is output. A feedback signal for hysteresis is given to 18b.

On the other hand, the light incident state is unstable, for example, the optical axis is deviated, or the window or the like of the device (not shown) is dirty, or the level of light projection or light reception is lowered due to adhesion of dust or the like. Or in the following case. That is, PD
If the light incident state to 13a to 13h is unstable, even if the light receiving signal exceeds the detection level of the light blocking detection circuit 18a, if it does not exceed the stable detection level of the stable light detection circuit 18b, Microcomputer 15
Is determined as "unstable light incident state".

At this time, the microcomputer 15
First, a lighting signal is output to the yellow LED 20b of the display circuit 20 to display the "unstable light incident state". Then, when this “unstable light incident state” is continuously detected, for example, for 5 seconds, the microcomputer 15 sets the yellow LED 20 b
And outputs an alarm signal to the alarm output circuit 19b for notification.

As a result, an unstable light incident state can be promptly detected to call attention, and erroneous detection can be prevented. b. Detection of Operating State of Shift Register In the light receiver 2, the microcomputer 15 detects whether there is any abnormality in the operating states of the shift registers 23a to 23h based on the output signal from the output terminal Q7 of the shift register 23h.

That is, if the shift registers 23a to 23h operate normally, the output terminal Q7 of the shift register 23h should output a signal as shown in FIG. The microcomputer 15 previously stores the input pattern in the normal operation. When the signal from the shift register 23h does not match the input pattern, the shift register 23a
It is determined that a failure has occurred in any of the devices 23 to 23h.
Then, the microcomputer 15 outputs a blinking signal to all the LEDs 20a to 20c of the display circuit 20 and provides an output signal to both the detection output circuit 19a and the alarm output circuit 19b to notify the "abnormal state". Perform

Thus, the shift registers 23a to 23a
If any one of the 3hs fails, it is possible to notify the occurrence of a malfunction such as the “H” level signal being kept output from the output terminal or the shift operation of the output signal not being performed. Further, the detection output is made to be in the same state as the light-shielded state due to the intrusion of the object, thereby acting on the safe side. This state is locked and maintained until the power is turned off. c. Detection of Operating State of Analog Switch As described above, the line check circuit 17 is connected to the output terminals of the analog switches 22a to 22h, and the comparison output is input to the microcomputer 15. And the microcomputer 15
Is the analog switch 22h as shown in FIG.
Is determined in accordance with a predetermined timing when the light receiving operation is not performed, that is, an output signal from the line check circuit 17 detected at two points of the ON state and the OFF state of the analog switch 22h.

The microcomputer 15 judges that the microcomputer 15 is operating normally when the output signal from the line check circuit 17 is inverted from the "H" level to the "L" level upon detection of the above two points. In this case, the output line to the detection circuit 18 is disconnected, or the analog switch 22a
It is determined that there is an “abnormal state”, for example, any one of the second through 22h remains on. When the microcomputer 15 determines the “abnormal state”, the microcomputer 15 outputs a blinking signal to all the LEDs 20 a to 20 c of the display circuit 20 and provides an output signal to both the detection output circuit 19 a and the alarm output circuit 19 b to “ An error is reported.

Thus, the line to the detection circuit 18, the shift registers 23a to 12h, the analog switch 22a
To 22h or any of the conversion circuits 21a to 21h can be quickly detected and notified. Further, the detection output is made to be in the same state as the light-shielded state due to the intrusion of the object, thereby acting on the safe side. This state is locked and maintained until the power is turned off.

The detection states by the various detection operations described above are summarized as shown in Tables 1 and 2 when they correspond to the respective display states of the light projector 1 and the light receiver 2.

[0060]

[Table 1]

[0061]

[Table 2] According to the present embodiment as described above, a certain period during which the light projecting operation by the light projector 1 is not performed is provided, and during this certain period, the light receiving signals of the PDs 13a to 13h of the light receiving device 2 are sequentially enabled, thereby disturbing the disturbance light. Since there is a notification when there is, it is possible to prevent erroneous detection due to disturbance light during the detection operation of the light blocking state, and to always perform an accurate detection operation.

Further, according to this embodiment, since the disturbance light is detected when the light projecting operation by the light projector 1 is not performed as described above, it is determined whether there is an adverse effect due to external noise or the like. Can be detected at the same time.

In the above-described embodiment, the detection of disturbance light is performed by providing a fixed period for detecting the PDs 13a to 13h collectively. However, the present invention is not limited to this. The detection may be performed each time the projection of the optical axis is completed.

In the above embodiment, the alarm output circuit 19b is provided. However, the present invention is not limited to this. The alarm output circuit 19b may be configured to notify by an indicator light or the like instead of the alarm output.

Further, in the above embodiment, the case where the present invention is applied to an area sensor having eight optical axes has been described. However, the present invention is not limited to this, and there are a plurality of pairs of light projecting elements and light receiving elements constituting the optical axis. Applicable to all things.

[0066]

As described above, according to the multi-optical axis photoelectric switch of the present invention, the inspection means converts the light receiving signals from the plurality of light receiving elements at the non-light emitting timing of the plurality of light emitting elements.
Since the light receiving state of the disturbance light is detected sequentially by detecting the light receiving state, the light receiving state of the disturbance light can be quickly detected. It has an excellent effect that it can be performed.

[Brief description of the drawings]

FIG. 1 is a block diagram of an overall configuration showing an embodiment of the present invention.

FIG. 2 is an electrical configuration diagram of a projector.

FIG. 3 is an electrical configuration diagram of a light receiver;

FIG. 4 is a time chart showing a signal output state of each part on the projector side;

FIG. 5 is a time chart showing a signal output state of each part on the light receiving side;

[Explanation of symbols]

1 is a light emitter, 2 is a light receiver, 3a to 3h are light emitting diodes (light emitting elements), 4 is a light emitting circuit, 5 is a microcomputer, 7 is a current detection circuit, 8 is a detection area, 9 is a display circuit, 11a to 11a. 11h is an AND circuit, 12a to 12h
Is a shift register, 13a to 13h are photodiodes (light receiving elements), 14 is a light receiving circuit, 15 is a microcomputer (control means and inspection means), 17 is a line check circuit, 18 is a detection circuit (judgment means), and 18a is light shielding. A detection circuit, 18b a stable light incident detection circuit, 18c a waveform shaping circuit, 19 an output circuit, 19a a detection output circuit, 19b an alarm output circuit, 20 a display circuit, 20a a red LED,
20b is a yellow LED, 20c is a green LED, 22a to 22h are analog switches, and 23a to 23h are shift registers.

Continuation of the front page (56) References JP-A-52-10575 (JP, A) JP-A-2-271198 (JP, A) JP-A-51-113262 (JP, A) JP-A-51-140283 (JP) , A) Japanese Utility Model Application Hei 4-19830 (JP, U) Japanese Utility Model Application Hei 5-74029 (JP, U) Japanese Utility Model Application Hei 2-108441 (JP, U) (58) Fields surveyed (Int. Cl. ⁷ , DB Name) H03K 17/78 H01H 35/00

Claims (1)

(57) [Claims] 1. A plurality of light emitting elements which are sequentially turned on at a predetermined timing so as to irradiate light toward a detection area, and are provided so as to form a pair with the light emitting elements, and are provided from the detection area. A plurality of light receiving elements that receive the light, and control means for validating the light receiving signals from each of these light receiving elements in synchronization with the lighting timing of the light emitting element that is a pair thereof,
Determining means for determining a light blocking state in the detection area based on a light receiving signal from the light receiving element; and receiving light receiving signals from the plurality of light receiving elements at non-light emitting timings of the plurality of light emitting elements. A multi-optical axis photoelectric switch, comprising: inspection means for sequentially validating and detecting a state of input of disturbance light into the detection area.