JPH11260215A - Photoelectric sensor and multiple optical axis photoelectric sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a photoelectric sensor capable of surely detecting mutual interference in a short time. SOLUTION: In a photoelectric sensor 10, a light projector 15 and a photosensor 16 are operated in synchronism with each other at a predetermined period. When an outside diagnostic input terminal 21 diagnoses the interference of the photoelectric sensor 10, first a light projection stopping unit stops light projection from the light projector 15. In this state, the photosensor 16 senses the light at the predetermined period. During two periods with a normal light projecting timing, it is discriminated as to whether or not there is incidence of disturbance light. If there is even only one light incidence, incidence is monitored further for five periods. When there was no light incident, a photosensing timing unit 26 shifts a photosensing timing from an original synchronizing signal, thereby detecting photosensing. When it is discriminated that even then there is no possibility of mutual interference, the photosensing timing is further shifted, thus discriminating the incidence of the disturbance light.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photoelectric sensor, and more particularly, to a photoelectric sensor capable of preventing malfunction due to mutual interference.

[0002]

2. Description of the Related Art A multi-optical axis photoelectric sensor has been conventionally used as a safety device for a press machine or an approach warning device in a danger zone. The multi-optical axis photoelectric sensor is arranged such that a light emitter having a plurality of light emitting elements and a light receiver having a plurality of light receiving elements corresponding to each of the plurality of light emitting elements face each other. By forming an optical axis between each of the plurality of light emitting elements and the plurality of light receiving elements, a large number of optical axes (optical paths) are formed between the light projector and the light receiver.
Then, a detection area is set between the light emitting device and the light receiving device, a plurality of light emitting devices are sequentially emitted, and the light receiving operation is performed in a state synchronized with the light emitting timing by the light receiving device corresponding to each light emitting device. It is. In a multi-optical axis photoelectric sensor, when a light-shielding object is present in the detection area, no light-receiving signal is generated by the light-receiving element. Therefore, it is possible to determine the light-shielded state of the optical axis based on the signal and output an object detection signal. And where the multi-optical axis photoelectric sensor is used,
To prevent accidents, such as by stopping the press device based on such an object detection signal, or by detecting the entry of a person into a danger zone into the factory and issuing an alarm. Have been.

When a plurality of photoelectric sensors are provided in close proximity, mutual interference may occur. Mutual interference detection of such a photoelectric sensor is disclosed in, for example, Japanese Patent Application Laid-Open No. 5-754.
No. 21 discloses this. According to the publication, a light receiving function is enabled during non-light emission during normal operation called a disturbance light detection state. When the frequency of light reception in the disturbance light detection state is low, a warning is issued. When the frequency of light reception in the disturbance light detection state is high, the output is set to the same state as the light-shielded state, and this state is maintained until the power is reset.

[0004]

A conventional photoelectric sensor detects disturbance light as described above. However, in this case, when the disturbance light is the mutual interference light from the photoelectric sensor of the same type as itself, it takes a long time to find the interference, because the light projection periods of the interfered side and the interfered side are very close. Therefore, the photoelectric sensor will fall out of function at an unexpected time, and if the machine controlled by the photoelectric sensor stops, or if you try to prevent mutual interference by changing the installation, until you confirm that it is correct with the new installation Because it takes a long time, the convenience may be reduced.

[0005] This state will be described with reference to the drawings. FIG. 9 is a diagram showing a light receiving timing (a) of the photoelectric sensor for detecting mutual interference light and a light projection timing (b) of disturbance light. Referring to FIG. 9, for example, in a multi-optical axis photoelectric sensor, the light emitting cycle (= light receiving cycle) of the sensor that receives disturbance light is 5 ms, and the light emitting cycle of the sensor that gives disturbance light is 5.001.
ms (relative error 0.02%). As shown in FIG. 9, since the light receiving timing (a) of the sensor and the emission timing (b) of the disturbance light are shifted by 0.001 ms, the two timings approach each other by 0.001 ms every cycle. Therefore, mutual interference can be detected only when t = 22.5 s. Assuming that the initial deviation between the disturbance light timing and the disturbance light detection timing is 4.5 ms,
The time required to detect the disturbance light is 5.001 ms × 4.
5 ms / 0.001 ms = 22.5 s When an algorithm for stopping the sensor output when disturbance light is detected is employed, there may be a situation in which the photoelectric sensor is stopped at any time. As a result, there is a problem in convenience for the user.

Further, if the light emission pulse width is 5 μs and the light receiving axis effective period is 10 μs, the duration of mutual interference is 5 m
s × (5 μs + 10 μs) /0.001 ms = 75 ms
It is. During this period, the sensor does not react even if the optical axis is interrupted, and is in a malfunction state.

The present invention has been made to solve the above problems, and has as its object to provide a photoelectric sensor capable of reliably detecting the presence or absence of mutual interference in a short time.

[0008]

According to a first aspect of the present invention, a light emitting unit and a light receiving unit operate synchronously at a predetermined cycle. The photoelectric sensor is means for stopping light emission of the light emitting unit, means for adjusting the phase of the light receiving cycle while receiving light at a predetermined cycle, and adjusting the light receiving unit with the adjusting means when the light emitting unit is not emitting light. Means for detecting disturbance light having a predetermined period, and display means for displaying when disturbance light detection means detects disturbance light.

In a state where the light projecting unit does not emit light, the light receiving unit shifts the phase of a predetermined cycle to receive the disturbance light, and detects the presence or absence of the disturbance light emitted at the predetermined cycle. A message to that effect is displayed. As a result, the detection of the photoelectric sensor having light of a predetermined cycle, that is, the presence or absence of mutual interference can be reliably detected in a short time.

A multi-optical axis photoelectric sensor according to a second aspect has a plurality of photoelectric sensors in which the light projecting unit and the light receiving unit operate synchronously at a predetermined cycle. The multi-optical axis photoelectric sensor includes means for stopping light emission of the plurality of light emitting units, means for adjusting the phase of the light receiving cycle while receiving light at a predetermined cycle in the plurality of light receiving units, and light emitting of the plurality of light emitting units. In the stopped state, a means for detecting a disturbance light having a predetermined cycle by adjusting the plurality of light receiving units by the adjustment means, and a display means for displaying the effect when the disturbance light detection means detects the disturbance light. Including.

In a multi-optical axis photoelectric sensor having a plurality of light projecting portions and a light receiving portion, a plurality of light receiving portions are shifted in phase by a predetermined period in a state where the light projecting portion does not emit light, and a disturbance light having a predetermined period is provided. Is detected, and when disturbance light is detected, the fact is displayed. Therefore, in a multi-optical axis photoelectric sensor,
Interference light that is being projected at a predetermined cycle can be reliably detected in a short time.

According to a third aspect of the present invention, the multi-optical axis photoelectric sensor has a plurality of light projecting units and a plurality of light receiving units, each forming a pair of optical axes and operating synchronously. The multi-optical axis photoelectric sensor includes a unit for selecting a desired optical axis among a plurality of optical axes, a unit for stopping light emission of the light emitting unit, and receiving light while receiving light at a predetermined cycle in the selected light receiving unit. Means for adjusting the phase of the cycle, means for adjusting the selected light receiving portion by the adjusting means in the light emission stop state of the light emitting means to detect disturbance light having a predetermined cycle, and detecting the disturbance light And display means for displaying that effect.

In a multi-optical axis photoelectric sensor having a plurality of light projecting units and a light receiving unit, a desired light axis is selected from the plurality of optical axes, and the light receiving unit selected in a state where the light projecting unit does not emit light is selected. Disturbance light emitted at a predetermined cycle is received while shifting the predetermined cycle. Then, when the disturbance light is received, the fact is displayed. As a result, it is possible to detect the presence or absence of interference of a desired optical axis among the plurality of optical axes.

In the multi-optical axis photoelectric sensor according to the fourth aspect, the display means of the multi-optical axis photoelectric sensor according to the third aspect performs a display capable of identifying the selected optical axis that has detected the disturbance light.

Since the display for identifying the optical axis from which the disturbance light is detected is performed, it is possible to detect which of the plurality of optical axes is causing interference.

In the photoelectric sensor according to a fifth aspect, the photoelectric sensor according to any one of the first to third aspects is connected to a predetermined device, and when the disturbance light detecting means detects disturbance light, a predetermined signal is output to the device. Output to

In the photoelectric sensor according to any one of the first to third aspects, after detecting the disturbance light once, the output of the device is kept in the same state as the light shielding state unless the disturbance light is not present. As a result, safety is reliably ensured in the device using the photoelectric sensor.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (i) First Embodiment An embodiment of the present invention will be described below with reference to the drawings.
FIG. 1 is a functional block diagram showing a main part of a single optical axis reflection type photoelectric sensor. Referring to FIG. 1, a reflective photoelectric sensor 10
Is a microcomputer 11 that achieves most of the functions of the photoelectric sensor, and a light emitting circuit 12 that is connected to the microcomputer 11 and controls an LED 15 that emits light.
A light receiving circuit 13 for inputting a signal received by a photodiode (hereinafter abbreviated as PD) 16 constituting a light receiving section, and an output circuit 1 for outputting a control output signal to a device (not shown)
4, a disturbance light receiving indicator 19 for displaying when disturbance light is detected by the PD 16, and an indicator lamp 18 for displaying ON / OFF. The microcomputer 11 further includes an EEPROM for storing data.
M23 is connected. The photoelectric sensor 10 further includes a power supply circuit 17, to which power is supplied via a power supply terminal 20.

The microcomputer 11 includes a light emitting timing unit 25 for instructing light emitting timing, a light receiving timing unit 26 for instructing light receiving timing, and a light emitting unit for stopping light emission at the time of diagnosis according to a signal from the external diagnostic input terminal 21. It has functions of a light stopping unit 24, a gate unit 27 for receiving light at a predetermined timing by the light receiving circuit 13 according to the light receiving timing unit 26, and a determining unit 28 for determining whether or not light is received by the light receiving circuit 13.

Light from the LED, which is usually the light projecting unit 15, is reflected by the detection object 40, and the detected light is reflected by the detection unit 1.
The determination unit 28 determines whether or not the detection object 40 is input by being input to the photodiode 6.

Light emission and light reception are synchronously controlled by a synchronization signal from the light emission timing section 25 to the light reception timing section 26. The photoelectric sensor 10 has an external diagnostic input terminal 21. When an external diagnostic function is selected from a device (not shown), the photoelectric sensor 10 stops emitting light and keeps the output in a safe state (OFF). At this time, the light receiving timing section 25 shifts the light receiving timing (phase) little by little as described later. The signal received by the PD as the light receiving unit 16 is amplified and filtered by the light receiving circuit 13 and then sent to the gate unit 27. The gate unit 27 passes the light reception signal to the determination unit 28 only during a period controlled by the light reception timing unit 26.

FIG. 6 shows the overall appearance of a single optical axis reflection type photoelectric sensor 81 to which the present invention is applied. FIG. 2 is a timing chart showing the relationship between the light receiving timing and the disturbance light timing at the time of external diagnosis. As a temporal condition, the light emitting cycle (= light receiving cycle) of the sensor is 100 μs and the light emitting pulse width is 10
μs, and the light receiving effective period is 10 μs.

Referring to FIG. 2, (a) shows the light receiving timing of the sensor when the external diagnostic function is selected, and (b) shows the timing of disturbance light.

Next, a procedure for detecting disturbance light (mutual interference light) will be described. It is determined whether or not light has entered during two periods at normal light emission timing.

If there is a light-in state even once, light-in monitoring is performed for another five cycles. According to the majority logic, for example, when the light incident state is detected in four or more cycles out of seven cycles, it is determined that there is disturbance light.
Thereafter, disturbance light detection is continued with the same phase. If it is determined that there is no disturbance light on the way, the detection of the presence or absence of light is started again.

In the case where the light-in state has never been detected and the light-in state is three times or less, the light-in timing is delayed by 5 μs with respect to the original synchronization signal (the phase shift is performed). ).

If it is determined that there is no disturbance light, the light reception timing is further delayed by 5 μs, and a total of 10 μs is delayed.

If it is determined that there is no possibility of mutual interference, the light receiving timing is further delayed by 5 μs, and
Delay 5 μs. Similarly, 20, 25,..., 95 μs
Delay. If it is still determined that there is no possibility of mutual interference, the delay time is set to 0 and the process is started again.

The above-mentioned one round processing time is a maximum of 0.1 ms.
× 7 cycles × 20 (delay processing) = 14 μs.

A specific example will be described with reference to FIG. As described above, when there is no light incident state, the light receiving timing (a) of the sensor when the external diagnostic function is selected is set to 5 μm.
s, that is, the phase is shifted (a1). Then, light is received in a normal 100 μs (a2). Here, it coincides with the disturbance light timing (b) at the point b1. b2
, The light incident state is detected in four or more cycles, so that the determination unit 28 determines that there is disturbance light. Then, the fact is displayed on the disturbance light reception indicator lamp 19. As this display state,
The disturbance light reception indicator lamp 19 may blink. The “light incident at the time of external diagnosis” information is recorded in the storage element of the EEPROM 23. This record is not erased by turning the power on and off, but is kept until "light shielding at the time of external diagnosis" is recorded. In other words, even if the EEPROM 23 stops selecting the external diagnostic function or keeps the power on or off while the information on the “light incident at the time of external diagnosis” is held, the output is in a safe state (in accordance with the “light incident at the time of external diagnosis”). OFF)
Is controlled. The “light shielding at the time of external diagnosis” information is recorded when the light shielding state lasts for 28 ms or more. 28 ms here
Is twice the maximum processing time of 14 ms described above, and light shielding information at the time of external diagnosis is recorded only when disturbance light is not received even after two rounds.

The photoelectric sensor 10 returns from the external diagnosis mode to the normal mode when the external diagnosis input signal is not received for a certain period after the information of "light shielding at the time of external diagnosis" is recorded.

(Ii) Second Embodiment FIG. 3 is a block diagram showing a main part of a control unit of a multi-optical axis photoelectric sensor. Referring to FIG. 3, the multi-optical axis photoelectric sensor 51 includes:
It includes a light emitter 52 and a light receiver 63. The projector 52 includes a microcomputer 55 for performing the main functions of the projector,
A sequential light emitting circuit 59 connected to the microcomputer 55 for outputting light emitting signals to the plurality of light emitting units LED1 to LED8, a disturbance light search indicator light 54 for displaying that the disturbance light search display is being performed; , And a power supply circuit 53. The microcomputer 55 includes a light emission timing unit 56 for controlling light emission timing and a light emission stop unit 5 for stopping light emission.
7 and a function of a transmission unit 58 for transmitting the fact to the light receiver 63 at the time of external diagnosis.

The light receiver 63 receives a light signal from a plurality of light receivers PD1 to PD8 and a microcomputer 69 for achieving a main function as the light receiver 63, and an optical axis selector capable of selecting a desired optical axis among them. Circuit 75 and an optical axis selection circuit 75 connected to a microcomputer 69
, An ON / OFF indicator 65, and a disturbance light receiver for displaying that disturbance light other than the light emitter 52 has been received. It includes an indicator light 66 and an output circuit 68 that outputs the result of determination of the presence or absence of disturbance light by the microcomputer 69 to an external device (not shown) via a control output terminal 77. An EEPROM 74 is connected to the microcomputer 69, in which predetermined data described later is recorded. The light receiver 63 includes a power supply circuit 64 to which power is supplied from the outside via a power supply terminal 76.

The microcomputer 69 receives a synchronization / external diagnosis instruction signal from the light projector 52, a light reception timing section 72 for setting a light reception timing received from the light projector 52 via the reception section, and a light reception timing. At this timing, the function of the gate unit 70 for passing the signal of the presence or absence of light reception from the light receiving circuit 67 and the function of the determination unit 71 for determining the presence or absence of disturbance light are performed.

The transmitter 58 of the light projector 52 and the receiver 73 of the light receiver 63 are connected by a cable for transmitting a synchronization / external diagnosis instruction signal 78.

The projector 52 has an external diagnostic input terminal 61. When the external input diagnostic function is not selected by an external device (not shown), a synchronization signal is transmitted to the optical receiver 63. When the external input diagnostic function is selected, an external diagnostic instruction signal is transmitted to the optical receiver 63. Send. Floodlight 52
Usually emits the LED of each optical axis sequentially,
When the external diagnosis function is selected, the light emission of all optical axes is stopped. The light receiver 63 is normally an LED 1 that is emitting light.
Select the light receiving signals of PD1 to PD8 of the optical axis corresponding to LED8. When the external diagnostic function is selected, select the light receiving signals of all optical axes simultaneously and set the output to the safe state (O
FF). At this time, the light receiving timing function shifts the light receiving timing (phase) little by little as described later. The signal received by the light receiving section PD is received by the light receiving circuit 67.
, And then sent to the gate unit 70. The gate unit 70 passes the light reception signal to the determination unit 71 only during a period controlled by the light reception timing unit 72.

FIG. 7 is an external view of a light projector 52 and a light receiver 63a constituting a multi-optical axis photoelectric sensor 51 according to the second embodiment. LED1 to LED8 of the light emitter 52 and the light receiver 63a
PD1 to PD8 constitute an optical axis 82, respectively.

FIG. 4 is a timing chart showing the relationship between the light receiving timing and the disturbance light timing at the time of external diagnosis in the multi-optical axis photoelectric sensor shown in FIG. (A) shows disturbance light, (b) shows a normal light receiving state, and (c) shows a light receiving state at the time of external diagnosis. Here, the disturbance light shown in (a) is the light emitted from the multi-optical axis photoelectric sensor having eight optical axes shown in FIG. 3, among which the light from the first optical axis (the optical axis of LED1 and PD1) is detected. Shall be.

(D) is an enlarged view of the disturbance light (a).
(E)-(i) is an enlarged view of a light receiving state at the time of external diagnosis of (c), (e) shows a state of t = 0 to 15 ms,
(F) shows a state at t = 15 to 30 ms, and (g) shows a state at t = 15 to 30 ms.
= 30 to 45 ms, and (h) shows t = 255 to
270 ms, (i) t = 270-285
ms.

Referring to FIG. 4, the light emitting cycle (= light receiving cycle) of the eight optical axis photoelectric sensor receiving the disturbance light is 5 ms, and the light emitting cycle of the eight optical axis photoelectric sensor providing the disturbance light is five times. 0.001 ms (relative error 0.02%), the selection switching interval of each optical axis is 100 μs, the initial deviation between the disturbance light timing and the disturbance light detection state timing is 85 μs, the light emission pulse width is 5 μs, and the light receiving axis is effective. The period is set to 10 μs. As optical conditions, it is assumed that disturbance light enters all the optical axes of the light receiver 63. The light receiving units PD1 to PD8 detect disturbance light (mutual interference light) by the following algorithm.

The entire optical axis is set to 100 ms for 5 ms × 3 cycles.
It is activated simultaneously every μs to determine the presence or absence of light (Fig. 4
(E)).

If the light incident state is detected in two or more of the three cycles, it is determined that there is disturbance light. Thereafter, the disturbance light detection function is continued with the same phase. If it is determined that there is no disturbance light on the way, the presence / absence determination of light is started again.

When the light incident state is one or less, the light reception timing is delayed by 5 μs with respect to the original synchronization signal (FIG. 4F) (phase shift).

When it is determined that there is no disturbance light, the light receiving timing is further delayed by 5 μs to delay the total by 10 μs, and the process is executed (FIG. 4G).

If it is determined that there is no disturbance light, the light receiving timing is further delayed by 5 μs to delay a total of 15 μs. Similarly, the delay is 20, 25,..., 95 μs (FIGS. 4H and 4I). If it is still determined that there is no disturbance light, the delay time is set to 0 and the process is started again.

The above-mentioned one round processing time is 5 ms × 3 periods × 20 (delay type) = 300 ms.
It is possible to detect disturbance light in 3 cycles × (85 μs / 5 μs + 1 + 1) = 285 ms.

As a result of the external diagnosis, the light receiver 63 performs some kind of display while it is detected that the light is incident. For example, the ON / OFF indicator light 65 is blinked. The “light incident at the time of external diagnosis” information is stored in a storage element such as the EEPROM 74. This record is not erased by turning on and off the power supply, and is kept until “light shielding at the time of external diagnosis” is stored. That is, even when the selection of the external diagnostic function is stopped or the power is turned ON / OFF while the light receiver 63 holds the “light incident at the time of external diagnosis”, the output is controlled according to the “light incident at the time of external diagnosis” information. You. At this time, the output is not in danger. The “light shielding at the time of external diagnosis” information is recorded when the light shielding state continues for 300 ms or more.

After the "light shielding at the time of external diagnosis" information is recorded, the light receiver 63 shifts from the external diagnosis mode to the normal mode at the time when an external diagnosis input signal is received from the projector 52 for a certain period of time. It waits for a start signal from the projector 52.

In FIG. 4, the disturbance light enlarged view of (d) is exactly 5.001 ms-5.0 m as described above.
A fraction of s = 1 μs should also be considered, but is omitted here. The light receiver 63 detects disturbance light at the time point indicated by i1 in (i).

(Iii) Third Embodiment Next, a third embodiment of the present invention will be described. Also in the third embodiment, the configuration of the multi-optical axis photoelectric sensor is the same as that of the second embodiment shown in FIG. FIG. 5 shows a third embodiment of the present invention.
FIG. 6 is a diagram illustrating a relationship between light reception timing of a light projector 52 and a light receiver 63 and disturbance light timing according to the embodiment. (A) shows disturbance light, (b) shows a normal light receiving state, and (c) shows a light receiving state at the time of external diagnosis. The disturbance light in (a) is emitted from a multi-optical axis photoelectric sensor having eight optical axes, and the light from the eighth optical axis (LED8-PD8) is detected.

Referring to (c), the disturbance light is reflected on the first optical axis (L
It is assumed that light enters ED1-PD1).

(D) is an enlarged view of the disturbance light shown in (a), and (e) to (i) are enlarged views for each time of the light receiving state (c) at the time of external diagnosis. (E) is t = 0 to 15 ms
(F) shows a state at t = 15 to 30 ms, (g) shows a state at t = 30 to 45 ms, and (h)
Indicates a state at t = 2055 to 2070 ms, and (i) indicates a state at t = 207 to 2085 ms. (D)
Since the disturbance light on the optical axis 1 and the optical axis 2 is not optically received as disturbance light, it is indicated by a dotted line. In addition, although a fraction of 5.001 ms−5.0 ms = 1 μs should be considered accurately, it is omitted here.

The difference of this embodiment from the second embodiment is that when the external diagnostic function is selected, the light receiver 63 sequentially selects the light receiving signal of each optical axis. In this embodiment, the light emitting cycle (= light receiving cycle) of the 8-optical axis photoelectric sensor that receives disturbance light under temporal conditions is 5 ms, and the light emitting cycle of the 8-optical axis photoelectric sensor that gives disturbance light is 5.001 ms.
(The relative error is 0.02%), and the selection switching interval of each optical axis is 10
0 μs, the initial deviation between the disturbance light timing and the disturbance light detection state timing is 685 μs, and the projection pulse width is 5 μm for each.
s, the light receiving axis effective period is 10 μs. Further, as optical conditions, it is assumed that disturbance light enters the first optical axis of the light receiver 63 from the eighth optical axis. Here, the initial deviation between the disturbance light timing and the disturbance light detection state timing is 685 μs, but it goes without saying that this value can be set arbitrarily.

Next, an algorithm for detecting disturbance light (mutual interference light) of the light receiver 63 will be described.

Each optical axis is sequentially enabled, and for 5 ms × 3 cycles, the presence / absence of disturbance light is detected for three cycles for each optical axis. The start cycle of each cycle is 1.667 ms (FIG. 5C).

If the light incident state is detected in two or more of the three periods, it is determined that there is disturbance light. Thereafter, the disturbance light detection function is continued with the same phase. If it is determined that there is no disturbance light on the way, the detection of the presence or absence of light is started again.

In the case where the light incident state is one or less, the light receiving timing is delayed by 5 μs with respect to the original synchronizing signal and executed (FIG. 5F).

If it is determined that there is no disturbance light, the light receiving timing is further delayed by 5 μs to delay the total by 10 μs, and the process is executed (FIG. 5G).

If it is determined that there is no disturbance light, the light receiving timing is further delayed by 5 μs to delay a total of 15 μs. In the same manner, the delay is delayed by 20, 25,..., 1660 μs. If it is still determined that there is no disturbance light, the delay time is set to 0 and the process is started again.

The above-mentioned one round processing time is 5 ms × 3 cycles × 333 (delay type) = 4995 ms.
s × 3 periods × (685 μs / 5 ms + 1 + 1) = 208
Disturbance light detection is possible in 5 ms.

In this embodiment, as shown in FIG. 6C, during the external diagnosis, the first to third cycles of the external diagnosis light reception are performed within 5 ms, which is one cycle of the disturbance light. Therefore, external diagnosis can be performed in a short time.

As a result of the external diagnosis, while it is detected that the disturbance light is in the incident state, the light receiver 63 performs some display on each optical axis. FIG. 8 is a diagram showing a configuration example of a multi-optical axis photoelectric sensor when such a display is performed. With reference to FIG. 8, the light receiver 63b is provided with a disturbance light reception indicator light 66 for each optical axis adjacent to the light receiving portion of each optical axis, and only the disturbance light reception indicator light of the optical axis that has detected disturbance light is provided. Flashes. Thereby, the installer of the photoelectric sensor can easily know which optical axis the disturbance light is incident on.

The embodiments disclosed this time are to be considered in all respects as illustrative and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a main part of a single-axis reflective photoelectric sensor.

FIG. 2 is a timing chart showing a relationship between a light receiving timing and a disturbance light timing at the time of external diagnosis in a single optical axis reflection type photoelectric sensor.

FIG. 3 is a block diagram showing a main part of a transmission type multi-optical axis photoelectric sensor.

FIG. 4 is a timing chart showing a relationship between a light receiving timing and a disturbance light timing at the time of external diagnosis in the transmission type multi-optical axis photoelectric sensor.

FIG. 5 is a timing chart showing a relationship between a light receiving timing and a disturbance light timing according to a third embodiment of the present invention.

FIG. 6 is a diagram illustrating an appearance of a single optical axis photoelectric sensor.

FIG. 7 is a diagram illustrating an installation example of a multi-optical axis photoelectric sensor.

FIG. 8 is a diagram showing an installation example of a multi-optical axis photoelectric sensor according to another embodiment of the present invention.

FIG. 9 is a diagram for explaining a conventional problem.

[Explanation of symbols]

 Reference Signs List 10 photoelectric sensor 11 microcomputer 12 light emitting circuit 13 light receiving circuit 14 output circuit 15 light emitting section (LED) 16 light receiving section PD (photodiode) 21 external diagnostic input terminal 23 EEPROM 31 light emitting timing section 32 light receiving timing section 33 light emitting Stop unit 34 Gate unit 35 Discrimination unit 40 Detected object 51 Transmission type multi-optical axis photoelectric sensor 52 Projector 55 Microcomputer 56 Projection timing unit 57 Projection stop unit 58 Transmission unit 61 External diagnostic input terminal 63 Receiver 66 Display of disturbance light reception Light 67 Light receiving circuit 68 Output circuit 69 Microcomputer 70 Gate unit 71 Judging unit 72 Light receiving timing unit 73 Receiving unit 74 EEPROM 75 Optical axis selection circuit

Claims (5)

[Claims] 1. A photoelectric sensor in which a light projecting unit and a light receiving unit operate synchronously at a predetermined cycle, comprising: means for stopping light emission of the light projecting unit; Means for adjusting the phase of the cycle; means for adjusting the light receiving section by the adjusting means to detect disturbance light having the predetermined cycle in a state where the light projecting section is in the light stop state; and the disturbance light detecting means. And display means for displaying when the device detects disturbance light. 2. A multi-optical axis photoelectric sensor having a plurality of photoelectric sensors in which a light projecting unit and a light receiving unit operate synchronously at a predetermined cycle, and means for stopping light emission of the plurality of light projecting units. A means for adjusting a phase of a light receiving cycle while receiving light at a predetermined cycle in the plurality of light receiving sections; and adjusting the plurality of light receiving sections by the adjusting means while the light projecting section is in a light stop state. A multi-optical axis photoelectric sensor, comprising: means for detecting disturbance light having a predetermined cycle; and display means for displaying when the disturbance light detection means detects disturbance light. 3. A multi-optical axis photoelectric sensor having a plurality of light projecting units and a plurality of light receiving units each forming a pair of optical axes and operating synchronously, wherein a desired one of the plurality of optical axes is provided. Means for stopping light emission of the plurality of light emitting units; means for adjusting the phase of a light receiving cycle while receiving light at a predetermined cycle in the light receiving unit of the selected optical axis; In the stopped state of the light unit, a unit that adjusts the selected light receiving unit by the adjusting unit to detect disturbance light having the predetermined period, and when the disturbance light detection unit detects the disturbance light, And a display means for displaying a message to the effect. 4. The multi-optical axis photoelectric sensor according to claim 3, wherein said display means includes a display means for displaying a selected optical axis that has detected said disturbance light. 5. The photoelectric sensor is provided in a predetermined device. When the disturbance light detecting means detects disturbance light, the photoelectric sensor outputs a signal to the predetermined device to take a predetermined light blocking state operation. The photoelectric sensor according to any one of claims 1 to 3, wherein the signal is output until the disturbance light detecting means stops detecting disturbance light.