JPH0575421A - Multi-axis photoelectric switch - Google Patents

Abstract

PURPOSE:To prevent mis-detection due to external disturbance light. CONSTITUTION:A non-light emission operating period is provided on a light projecting operation for LEDs(light emitting diodes) 3a-3h of a light projecting device 1. A microcomputer 15 activates sequentially a light receiving signal from PD(photodiodes) 13a-13h of a light receiving device 2 to detect the presence of the light incidence state. Thus, the light from a light source other than the LEDs 3a-3h is discriminated to be received by detecting the light incidence state. Thus, the state is quickly coped with and mis-detection due to an external disturbance light is prevented at the detection of the light interruption state.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is provided with a plurality of pairs of a light emitting element and a light receiving element, and activates a light receiving signal from a light receiving element which forms a pair in synchronization with lighting of the light emitting element in a detection area. The present invention relates to a multi-optical axis photoelectric switch adapted 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 / absence of an object in a wide detection area and is therefore used, for example, as a safety device for a press machine. The schematic structure is as follows. That is, a plurality of pairs of light emitting elements and light receiving elements forming a pair are provided, and one light emitting element is sequentially emitted toward the detection area in response to 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 element which is emitting light among these light receiving element groups has the light emission timing of the light emitting element. It is activated by the selection circuit synchronously.

The received light signal that has passed through the selection circuit from the light receiving element is amplified by the light receiving amplifier and compared with a predetermined reference level by the comparison circuit, and when it is determined that the amount of light received by 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 projecting element emits light, only the light receiving signals from the pair of light receiving elements are 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 which forms a pair with the light projecting element, and may be incident on the light receiving element provided in the vicinity thereof as light of relatively high intensity. Therefore, if the light receiving signals from all the light receiving elements are equally input to one comparison circuit, it is determined that the object is in the light receiving state even though its optical axis is in the light blocking state due to the intrusion of the object, and This is because the intrusion cannot be detected accurately.

[0005]

However, even when the detection operation is performed in the state where the pair of 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 the optical axis formed by a pair of a light emitting element and a light receiving element and is in a light blocking state, the light receiving element receives light from the light emitting element. It should be in a non-light-incident state by not entering, but at this time, when external light such as light from another sensor, sputtered light, or light from a lighting fixture enters the light-receiving element as ambient light, The light blocking state may not be detected due to the determination that the light is entering.

The detection of the light receiving state even in the light-shielded state as described above causes a problem that the device operates on the dangerous side when used as a safety device.

The present invention has been made in view of the above circumstances, and an object thereof is to quickly eliminate the adverse effect of the ambient light by detecting the light entering state due to the ambient light, and thus to shield the light. It is an object of the present invention to provide a multi-optical axis photoelectric switch that can always detect a state accurately.

[0009]

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 to a detection area, and these light emitting elements. A plurality of light receiving elements that are provided so as to form a pair with the elements and receive the light from the detection area, and the light receiving signals from these light receiving elements are activated in synchronization with the lighting timing of the light projecting elements forming the pair. Control means for judging, a judging means for judging a light shielding state in the detection area based on a light receiving signal from the light receiving element, and a light receiving signal from the light receiving element for activating at a non-light projecting timing of the light projecting element. The present invention is characterized in that it is provided with an inspection means for detecting the incoming state of ambient light into the detection area.

[0010]

According to the multi-optical axis photoelectric switch of the present invention, the control means sequentially operates each pair of the plurality of light emitting elements and the light receiving elements to detect the light shielding state in the detection area. Detects the light-receiving signal from the light-receiving element at a non-light-projecting timing of the light-projecting element to detect whether or not a light source other than the light-projecting element, that is, a light entering state due to ambient light. As a result, in the operation of detecting the light-shielded state by the control means, it is possible to quickly eliminate erroneous detection or the like due to ambient light, so that accurate detection can be performed.

[0011]

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

FIG. 1 shows the outline of the electrical structure. This area sensor is composed of a projector 1 and a photoreceiver 2 which are electrically separated.

First, in the projector 1, eight LEDs (light emitting diodes) 3a to 3h, which are a plurality of projector elements, are connected to a microcomputer 5 via a projector circuit 4. The DC power supply circuit 6 is connected to the microcomputer 5 and also to the light projecting circuit 4 via the current detection circuit 7 so as to be supplied with 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 energized current and two comparators to which the terminal voltage is applied. When the terminal voltage is within a predetermined range, One of the comparators inputs an "H" level signal and the other comparator inputs an "L" level signal to the microcomputer 5.

As will be described later, the microcomputer 5 is adapted to give a light projecting signal to the LEDs 3a to 3h via the light projecting circuit 4, and the LEDs 3a to 3h respectively have eight optical axes directed toward the detection area 8. Light for detection is sequentially projected.

A display circuit 9 for displaying the operating 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 given from the microcomputer 5 in accordance with the operating state of the projector 1 as described later.

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

The data input terminal D of the 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, and so on.
The output terminal and the data input terminal of 12 to 12h are sequentially connected. The output terminal Q of the shift register 12h
7 is connected to the microcomputer 5. Also,
Each clock input terminal CK of the shift registers 12a to 12h is connected to the output terminal C of the microcomputer 5.

The light projecting circuit 4 is divided into a main circuit section 4a for projecting and driving the LEDs 3a to 3d and a sub circuit section 4b for projecting and driving the LEDs 3e to 3h. In the present embodiment, 8 is provided. Two circuit parts 4 for the optical axis
It is used in a state where a and 4b are serially connected. 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, which are a plurality of light receiving elements, are provided.
Are connected to the microcomputer 15 via the light receiving circuit 14. The microcomputer 15 has the functions of both control means and inspection means. The DC power supply circuit 16 is connected to the microcomputer 15 and supplies power with a predetermined DC voltage. Further, the PDs 13a to 13h are arranged toward the detection area 8 so as to be paired with the LEDs 3a to 3h, respectively.

The output line of the light receiving circuit 14 is connected to the microcomputer 15 via the line check circuit 17, and is also connected to the microcomputer 15 via the detection circuit 18 which is a judging means. The microcomputer 15 is connected to an output circuit 19 for outputting the 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 constructed in detail as shown in FIG. That is, each PD 13a to 13h
A conversion circuit 21a for converting the received light signal into an electric signal, respectively.
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 the 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 according to the output voltage of the analog switches 22a to 22h in the ON state and an "L" level output according to the output voltage of the OFF state. It is like this.

Data input terminal D of the 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
Connected to 5. Further, each clock input terminal CK of the shift registers 23a to 23h is connected to the output terminal b of the microcomputer 15.

The light receiving circuit 14 includes PDs 13a to 13a.
a main circuit portion 14a for receiving a light receiving signal from d, and P
The sub-circuit section 14b for receiving the light receiving signals from D13e to 13h is separately provided. In this embodiment, two circuit sections 14a and 14b are used for eight optical axes 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 comparator circuit 18b for stable incident light detection, and a waveform shaping circuit 18c, each of which receives a detection signal from the light receiving circuit 14 and outputs its output.
Give to 5. From the microcomputer 15,
A feedback signal for hysteresis is applied to each of the circuits 18a to 18c.

When the light receiving signal exceeding a predetermined light incident detection level is given, the light-shielding detecting comparison circuit 18a outputs an "H" level signal indicating the light incident state to the microcomputer 1
It is designed to output to 5. The comparator circuit 18b for stable light incident detection is set to a stable light incident detection level higher than the above-mentioned light incident detection level. When a light receiving signal exceeding this stable light incident detection level is given, the stable light incident state is reached. Is supplied to the microcomputer 15. Further, the waveform shaping circuit 18c is adapted to give a synchronization detection signal to the microcomputer 15 when a burst signal is given as a light receiving signal as described later.

The output circuit 19 is composed of a detection output circuit 19a that outputs a light-shielding detection signal and an alarm output circuit 19b that notifies the unstable light incident state. In response to an output signal from the microcomputer 15, The output is given to a load (not shown) connected to the output terminal.

The display circuit 20 has three LEDs 20a, 2
0b and 20c, for example, the LED 20a is red, the LED 20b is yellow, and the LED 20c is green. These LEDs 20a to 20c are responsive to a display output signal from the microcomputer 15
By operating in a mode such as lighting, extinguishing, or blinking, each is driven in various modes indicating a light receiving state as described later.

Next, the operation of the present embodiment will be described by referring to FIGS. 4 and 5 separately for each operation in one cycle (for example, one cycle of 5 msec) shown below. That is,
(1) Standby state, (2) Sync signal detection, (3) Ambient light detection operation, (4) Light shielding state detection operation, (5) Light emitting state detecting operation, and (6) Light receiving state detecting operation is there.

The time chart of FIG. 4 shows the output signals from the respective parts of the microcomputer 5 in the projector 1 and the output states of the respective parts of the light projecting circuit 4, and the parts indicated by A to K in FIG. Corresponds to the output state. The time chart of FIG. 5 shows the output signals from the respective parts of the microcomputer 15 in the light receiver 2 and the output states of the respective parts of the light receiving circuit 14, and in FIG.
This corresponds to the output state of the part indicated by 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 the 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 becomes "H" level (see FIG. 4D), and A
The "H" level signal is applied to one input terminal of the ND circuit 11a. As a result, when the "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 light receiver 2, the microcomputer 15 inputs a pulse signal to the data input terminal D0 of the shift register 23a (see FIG. 5A), and also inputs it 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. 5C),
The analog switch 22a becomes conductive. As a result, the conversion circuit 21a becomes ready to output the light reception signal detected by the PD 13a to the detection circuit 18.

Then, as described above, the light projected from the LED 3a is set in the standby state where it can be detected by the PD 13a. (2) Sync signal detection The microcomputer 5 of the projector 1 includes an AND circuit 11
A burst signal for synchronization is output to each of the other input terminals a to 11h (see FIG. 4A). This allows the LED
3a is driven by the drive circuit 10a and projects the light for synchronous detection toward the detection area 8.

On the other hand, in the light receiver 2, the light for synchronous detection projected on the detection area 8 by the LED 3a is transmitted to the PD 1
When received by 3a, the received light signal is input to the waveform shaping circuit 18c via the conversion circuit 21a and the analog switch 22a. The waveform shaping circuit 18c inputs the synchronization detection signal to the microcomputer 15 when the level of the received light signal reaches a predetermined value.

As a result, the microcomputer 15
Receives a synchronization detection signal, judges that this is a signal of a predetermined length, and outputs a control signal to the light receiving circuit 14 at a predetermined timing in order to perform a predetermined detection operation described below. become. (3) Detecting operation of ambient light In the projector 1, the microcomputer 5 is kept in a state of not outputting a signal for a certain period after outputting the burst signal. That is, the "L" level signal is applied to the other input terminal of each of the AND circuits 11a to 11h, and all the LEDs 3a to 3h are turned off.

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

In the shift registers 23a to 23h, the state of "H" level signal output is shifted from the output terminals Q0 to Q7 each time a clock signal is applied (FIGS. 5C to 5J). reference). As a result, the state where the analog switch 22a is in the conducting state is sequentially shifted to the conducting 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.

Since the light is not emitted from the projector 1, the light receiving signal should not be detected by the above operation. However, when the light receiving signal is detected in this state, the light emitting device 1 is not detected.
Light from other light sources, that is, ambient light, is detected. When the ambient light is detected in this way, the microcomputer 15 causes the red LED 20 of the display circuit 20 to
The "a" level signal is output to the alarm output circuit 19b while giving a blinking signal to "a" to notify the "disturbance light detection state".

When the detection frequency is low, that is, when the detection is performed even once even in a short time, the above-mentioned "disturbance light detection state" is continued for, for example, 6 μsec or more. , Or if it is detected continuously in three cycles, it is determined that the detection frequency is high, and the microcomputer 15 outputs a detection signal to the detection output circuit 19a in addition to the above. In other words, the detection output is made to be in the same state as the light-shielded state due to the intrusion of the object so that it can be operated on the safe side. Further, this output state is locked and maintained until the power is turned off.

In this case, a time of about 800 μsec is set as the fixed period for detecting the ambient light. (4) Detecting Operation of Light-Shielding State When the ambient light detecting operation is completed, the microcomputer 5 in the projector 1 sequentially outputs pulse signals to the other input terminals of the AND circuits 11a to 11h at predetermined intervals (see FIG. (See A)), the clock signals are 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 applied to the AND circuit 11a.

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

As a result, a signal of "H" level is output from the output terminal Q0 of the shift register 23a to bring the analog switch 22a into a conductive state and validate the detection signal of the PD 13a. Therefore, when the above-mentioned LED 3a is turned on,
If the optical axis is not blocked by intrusion of an object, LED
The light projected from 3a is detected by the PD 13a, and is “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 the object enters and blocks the light projected from the LED 3a, the light receiving signal is not output, so the microcomputer 15 stores that the light blocking is detected once. Then, when the light-shielding detection continues twice or more, the microcomputer 15 determines that the light-shielding state has occurred, turns on the red LED 20a of the display circuit 20, and outputs an output signal to the detection output circuit 19a. ing.

Hereinafter, the LEDs 3b to 3h and the PD 13b will be described.
Each of the pairs from 13h to 13h is sequentially operated to transmit and receive the 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) Light emitting state detection operation a. Detecting Operation State of Shift Register In the projector 1, the microcomputer 5 detects whether or not the operation states of the shift registers 12a to 12h are abnormal 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. 4 (K) to the microcomputer 5. The input pattern in the normal operation is stored in advance in the microcomputer 5, and when the signal from the shift register 12h does not match the input pattern, it means that a failure has occurred in any of the shift registers 12a to 12h. Judgment is made and a blinking signal is output to the LED 9a of the display circuit 9 and all the light projecting operations are stopped.

As a result, the shift registers 12a to 1
It is possible to notify that a malfunction occurs such that the "H" level signal is still output to the output terminal or the output signal shift operation is not performed due to the failure of any of 2h. Moreover, all the light projecting operations are stopped, and the same state as the light blocking state due to the entry of an object is made to work on the safe side. Then, this state is locked and maintained until the power is turned off. b. Detection of Multiple Projection Abnormality As described above, the energization of the LEDs 3a to 3h is performed through the current detection circuit 7, and if the detection voltage appearing according to the energization current is within the predetermined range, two comparators are provided. Output detection signals of "H" level and "L" level, respectively. When the lighting operation is normally performed, the LEDs 3a to 3h are sequentially lit one by one, so that the energization current value at the time of lighting is within a certain range and the two LEDs are lit. The comparator should have output signals of "H" level and "L" level, respectively.

When the microcomputer 5 energizes and lights each of the LEDs 3a to 3h, the detection signal from the current detection circuit 7 is "H" level and "L".
When the level is determined to be normal, otherwise it is determined to be an "abnormal state", a blinking signal is output to the LED 9a of the display circuit 9, and all the light projecting operations are stopped.

As a result, the shift registers 12a to 1
2h, AND circuits 11a to 11h or drive circuit 10a
It is possible to promptly detect and notify a state in which any one of the LEDs 3a to 3h fails and two or more LEDs 3a to 3h are turned on at the same time, or no LEDs are turned on at the same time. Also,
All the light projecting operations are stopped (when two or more are turned on), and the same state as the light blocking state due to the entry of an object is made to work on the safe side. The light emission stopped state is locked and maintained until the power is turned off. (6) Detection operation of light receiving state a. Light-Incoming (Light-Receiving) Level Detection In the light receiver 2, the light-receiving signals from the PDs 13a to 13h are also input to the stable light-incoming detection circuit 18b. Then, as described above, the stable detection level in the stable incident light detection circuit 18b is set to a level higher than the detection level of the light shielding detection circuit 18a.

When the received light signal is given, the stable light-in detection circuit 18b compares its level with the stable detection level, and outputs P
When the level of the light receiving signal from D13a to 13h exceeds the stable detection level, the microcomputer 15 outputs the detection signal indicating the "stable light entering state". Further, in response to this, the microcomputer 15 determines that all PDs 1
When a detection signal indicating the "stable light input state" from 3a to 13h is obtained, a lighting signal is output to the green LED 20c of the display circuit 20 to notify the "stable light input state", and the stable light input detection circuit A feedback signal for hysteresis is given to 18b.

On the other hand, an unstable light receiving state, for example, the optical axis is deviated, or the window portion 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. When it does, it operates as follows. That is, PD
If the light entering state of 13a to 13h is unstable, even if the received light signal exceeds the detection level of the light shielding detection circuit 18a, it does not exceed the stable detection level of the stable light entering detection circuit 18b. Microcomputer 15
Is determined to be “unstable light input 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, for example, 5 seconds, the microcomputer 15 causes the yellow LED 20b.
A blinking signal is output to and an output signal is given to the alarm output circuit 19b to notify.

As a result, an unstable light entering state can be promptly detected to call attention, and erroneous detection can be prevented. b. Detecting Operating State of Shift Register In the photodetector 2, the microcomputer 15 detects whether the operating state of the shift registers 23a to 23h is abnormal based on the output signal from the output terminal Q7 of the shift register 23h.

That is, if the shift registers 23a to 23h are operating normally, the output terminal Q7 of the shift register 23h should output a signal as shown in FIG. 5 (j) to the microcomputer 15. The microcomputer 15 previously stores the input pattern at the time of normal operation. When the signal from the shift register 23h does not match the input pattern, the shift register 23a is stored.
It is determined that a failure has occurred in any one of to 23h.
Then, the microcomputer 15 outputs a blinking signal to all the LEDs 20a to 20c of the display circuit 20 and gives an output signal to both the detection output circuit 19a and the alarm output circuit 19b to notify that it is in the "abnormal state". Do.

As a result, the shift registers 23a to 23a
It is possible to notify that a malfunction occurs such that the "H" level signal is still output to the output terminal or the output signal is not shifted due to the failure of any of 3h. In addition, by making the detection output the same as the light-shielded state due to the intrusion of an object, it works on the safe side. Then, 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 thereof is input to the microcomputer 15. Then, the microcomputer 15
Is an analog switch 22h, as shown in FIG.
Output voltage is determined at a predetermined timing when the light receiving operation is not performed, that is, in accordance with the 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 determines that the output signal from the line check circuit 17 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, and otherwise In this case, the output line to the detection circuit 18 is broken, or the analog switch 22a
It is determined to be in an “abnormal state” such as any one of to 22h remains on. When the microcomputer 15 determines the "abnormal state", it outputs a blinking signal to all the LEDs 20a to 20c of the display circuit 20, and outputs an output signal to both the detection output circuit 19a and the alarm output circuit 19b. It notifies that it is "abnormal state".

As a result, the line to the detection circuit 18, the shift registers 23a to 12h, and the analog switch 22a.
22h or any one of the conversion circuits 21a to 21h has a failure, it can be quickly detected and notified. In addition, by making the detection output the same as the light-shielded state due to the intrusion of an object, it works on the safe side. Then, this state is locked and maintained until the power is turned off.

The detection states obtained by the various detection operations described above are summarized 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 constant period during which the light projecting operation by the light projector 1 is not performed is provided, and the light receiving signals of the PDs 13a to 13h of the light receiver 2 are sequentially validated during this constant period, whereby the ambient light Since the notification is given when there is, it is possible to prevent erroneous detection due to ambient light during the detection operation of the light-shielded state, and always perform an accurate detection operation.

Further, according to the present embodiment, since the ambient light is detected when the light projecting operation of the light projector 1 is not performed as described above, whether or not there is an adverse state due to external noise or the like. It can be detected at the same time.

In the above embodiment, the ambient light is detected with a fixed period for collectively detecting the PDs 13a to 13h, but the invention is not limited to this. For example, one optical axis or a plurality of optical axes may be used. It may be detected every 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, and the alarm output circuit 19b may be replaced by an indicator lamp or the like.

Further, in the above-mentioned embodiment, the case where the present invention is applied to the 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 a light projecting element and a light receiving element constituting the optical axis. It can be applied to all things.

[0066]

As described above, according to the multi-optical axis photoelectric switch of the present invention, the detection area is made effective by the light receiving signal from the light receiving element at the non-light emitting timing of the light emitting element. Since the light entering state of the ambient light is detected, it is possible to quickly detect the light entering state of the ambient light, and therefore, it is possible to obtain the excellent effect that the detection operation of the light blocking state can always be performed accurately. Play.

[Brief description of drawings]

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

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

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 receiver 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, and 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, inspection means), 17 is a line check circuit, 18 is a detection circuit (judgment means), and 18a is a light shield. Detecting circuit, 18b stable light detecting circuit, 18c waveform shaping circuit, 19 output circuit, 19a detection output circuit, 19b alarm output circuit, 20 display circuit, 20a 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.

Claims (1)

[Claims] 1. A plurality of light emitting elements which are sequentially turned on at a predetermined timing to irradiate light to the detection area, and a plurality of light emitting elements which are provided so as to be paired with these light emitting elements and which are provided from the detection area. A plurality of light receiving elements that receive the light of, and a control unit that activates the light receiving signals from each of the light receiving elements in synchronization with the lighting timing of the light projecting elements that form the pair,
Judging means for judging the light blocking state in the detection area based on the light receiving signal from the light receiving element, and validating the light receiving signal from the light receiving element at the non-light projecting timing of the light projecting element into the detection area. And a multi-optical axis photoelectric switch comprising an inspection means for detecting the incoming state of ambient light.