JPH0574029U - Multi-axis photoelectric switch - Google Patents

Abstract

(57) [Summary] [Purpose] To quickly detect the multiple projection state of the projector 1 with a simple configuration. [Structure] In the current detection circuit 7, LEDs 3a to 3
The current detecting resistor 7a detects the load current flowing through h.
The detected load currents are compared by comparators 7b and 7c and input to the microcomputer 5. When the outputs from the comparators 7b and 7c are at the "H" level and the "L" level, the microcomputer 5 determines that the load current is required to light one LED, and determines that the normal state, otherwise. In the case of, it is determined that there are two or more lighting states or an abnormal state in which no one is lighting. Therefore, the LED 3a
It is possible to quickly detect an abnormal state of the lighting operation for 3 to 3 hours.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 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 the light receiving element forming a pair in synchronization with the lighting of the light emitting element in the detection area to make the light shielding state in the detection area. The present invention relates to a multi-optical axis photoelectric switch adapted to detect.

[0002]

[Prior Art]

 Since this type of photoelectric switch can detect the presence or absence of an object in a wide detection area, it is used, for example, as a safety device of 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. At the same time, it is enabled by the selection circuit.

In this case, in order to sequentially turn on the light emitting elements, for example, a shift register is connected to each of the light emitting elements, and these shift registers are serially connected. Then, the clock signal is output from the control circuit, and the output state of the shift register is sequentially shifted at the output timing. Further, such a configuration is also used in the selection circuit described above.

A light receiving signal from the light receiving element is amplified by a light receiving amplifier and then input to a comparison circuit via a selection circuit, and compared with a predetermined reference level by the comparison circuit, so that the amount of light received by any one of the light receiving elements becomes low. When it is determined that the object has entered, 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 is emitting 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 also be incident on the light receiving element provided in the vicinity thereof as relatively high intensity light. Therefore, if the light receiving signals from all the light receiving elements are input to one comparison circuit equally, it is determined that the light receiving state is reached due to the intrusion of an object even though its optical axis is in the light blocking state. It is not possible to accurately detect the invasion of.

[0006]

[Problems to be solved by the device]

 However, on the light projecting side, for example, if a failure occurs in the circuit that drives the light projecting element, even if the shift register is operating normally, the light projecting elements will not be lit one by one at the specified timing. A problem occurs.

In this case, when two or more light projecting elements are turned on at the same time, even if there is an intruder blocking the optical axis, the light from other light projecting elements is not blocked and the There is a risk that light may enter the light receiving element. Then, on the light-receiving side, the light-shielded state cannot be determined because there is a light incident signal from the light-projecting element.

The present invention has been made in view of the above circumstances, and an object thereof is to detect a lighting state of a light projecting element with a simple configuration and prevent erroneous detection due to occurrence of a multiple light projecting state and to block light. (EN) Provided is a multi-optical axis photoelectric switch capable of surely detecting a state.

[0009]

[Means for Solving the Problems]

 The multi-optical axis photoelectric switch of the present invention is provided so as to form a pair with a plurality of light emitting elements which are sequentially turned on at a predetermined timing so as to emit light toward a detection area. A plurality of light receiving elements for receiving light from the detection area, control means for synchronizing the light receiving signals from the respective light receiving elements with the lighting timing of the light projecting elements forming a pair, and the light receiving elements. Judging means for judging the light shielding state in the detection area based on the light receiving signal from the element, current detecting means for detecting the load current supplied to the plurality of light projecting elements, and the current value detected by the current detecting means Has a feature in that it is provided with a state detecting means for determining whether or not is within a predetermined range.

[0010]

[Action]

 According to the multi-optical axis photoelectric switch of the present invention, the load currents of a plurality of light emitting elements which are sequentially turned on at a predetermined timing are detected by the current detecting means, and the detected current value at this time is detected by the state detecting means within a predetermined range. It is determined whether or not Thereby, for example, when the load current is detected beyond the range of the load current required for lighting one light projecting element, that is, when a plurality of light projecting elements are simultaneously lighted at a certain lighting timing. By detecting the multiple light emission state, quick response is possible, and the reliability of the light-shielded state detection operation is improved.

[0011]

【Example】

 An embodiment in which the present invention is applied to an area sensor with eight optical axes used in a safety device of a press device will be described below with reference to the drawings.

FIG. 3 shows a schematic electrical configuration. 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) 3 a to 3 h, which are a plurality of projector elements, are connected to a microcomputer 5 as a state detecting means via a projector circuit 4. The DC power supply circuit 6 is connected to the microcomputer 5 as well as to the light projecting circuit 4 via the current detection circuit 7 which is a current detection means. As shown in FIG. 1, the current detection circuit 7 includes, for example, a current detection resistor 7a that obtains a terminal voltage in proportion to the applied current, and two comparators 7b and 7c to which the terminal voltage is applied. When the terminal voltage is within a predetermined range, the comparator 7b inputs an "H" level signal and the comparator 7c 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 3 a to 3 h via the light projecting circuit 4, and each of the LEDs 3 a to 3 h emits eight light beams toward the detection area 8. Light for axis 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. 1), and a display signal is given from the microcomputer 5 according to the operating state of the projector 1 as described later.

Now, the light projecting circuit 4 described above is configured as shown in FIG. That is, drive circuits 10a to 10h for driving the respective 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 connected to the output terminals Q0 to Q7 of each of the light-projecting shift registers 12a to 12h, and the other input terminal of each of the AND circuits 11a to 11h is connected to the micro computer 5. Is connected to the output terminal A of.

The data input terminal D0 of the light projecting shift register 12a 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 light projecting shift register 12b, and so on. The output terminals and the data input terminals of the optical shift registers 12c to 12h are sequentially connected. The output terminal Q7 of the light emitting shift register 12h is connected to the microcomputer 5. Further, each clock input terminal CK of the light-projecting 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 this embodiment, The two circuit parts 4a and 4b 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 4b.

Next, in the light receiver 2, the eight PDs (photodiodes) 13a to 13h, which are a plurality of light receiving elements, are connected to the microcomputer 15 as a control means via the light receiving circuit 14. The DC power supply circuit 16 is connected to the microcomputer 15 and supplies power with a predetermined DC voltage. 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 as 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 inside the detection area 8 is determined.

Now, the above-mentioned light receiver 2 is configured in detail as shown in FIG. That is, conversion circuits 21a to 21h for converting the received light signals into electric signals are connected to the PDs 13a to 13h, respectively. The conversion circuits 21a to 21h are 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 light receiving shift registers 23a to 23h are connected to the gates of the analog switches 22a to 22h, respectively.

The line check circuit 17 described above outputs to the microcomputer 15 an “H” level output depending on the output voltage of the analog switches 22a to 22h in the ON state and an “L” level output depending on the output voltage in the OFF state. It is designed to give.

The data input terminal D0 of the light receiving shift register 23a is connected to the output terminal a of the microcomputer 15, the output terminal Q0 is connected to the data input terminal D of the light receiving shift register 23b, and so on. Shift registers 23c to 23h are serially connected. The output terminal Q7 of the light receiving shift register 23h is connected to the microcomputer 15. The clock input terminals CK of the light-receiving shift registers 23a to 23h are connected to the output terminal b of the microcomputer 15.

The light receiving circuit 14 is divided into a main circuit portion 14a that receives the light receiving signals from the PDs 13a to 13d and a sub circuit portion 14b that receives the light receiving signals from the PDs 13e to 13h. In the above, the two circuit portions 14a and 14b are used in a serially connected state for eight optical axes. 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 composed of a comparison circuit 18a for detecting light shielding, a comparison 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, The output is given to the microcomputer 15. Further, a feedback signal for hysteresis is applied from the microcomputer 15 to each of the circuits 18a to 18c.

The light-shielding detection comparison circuit 18 a outputs an “H” level signal to the microcomputer 15, which indicates a light incident state, when a light receiving signal exceeding a predetermined light incident detection level is given. There is. The comparator circuit 18b for stable incident light detection is set to a stable incident light detection level higher than the above-described incident light detection level, and when a light reception signal exceeding this stable incident light detection level is given, stable incident light detection is performed. An "H" level signal indicating the optical state is given 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 an output circuit 19 a for detecting output of light shielding and an alarm output circuit 19 b for notifying an unstable light incident state, and outputs according to an output signal from the microcomputer 15. The output is given to the load (not shown) connected to the terminal.

The display circuit 20 is composed of three LEDs 20a, 20b, 20c. For example, the LED 20a is red, the LED 20b is yellow, and the LED 20c is green. The LEDs 20a to 20c are operated in a lighting, extinguishing, or blinking mode in accordance with a display output signal from the microcomputer 15, so that the LEDs 20a to 20c have various light receiving states as will be described later. It is designed to be driven.

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 at 5 msec) shown below. That is, (1) standby state, (2) synchronization signal detection, (3) ambient light detection operation, (4) light blocking state detection operation, (5) light emitting state detection operation, and (6) light receiving state detection It is an action.

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. The parts indicated by A to K in FIG. Corresponds to the output state of. 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 the output states of the parts indicated by a to j in FIG. Equivalent to. (1) Standby State First, in the projector 1, the microcomputer 5 inputs a pulse signal to the data input terminal D of the light-projecting shift register 12a (see FIG. 4B), and the light-projecting shift register 12a through A clock signal is input to the clock input terminal CK of 12h (see FIG. 4C).

As a result, the output terminal Q0 of the light emission shift register 12a becomes "H" level (see FIG. 4D), and the "H" level signal is input to one input terminal of the AND circuit 11a. It will be in the given state. 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 D of the light receiving shift register 23a (see FIG. 5A), and also receives the clocks of the light receiving shift registers 23a to 23h. The clock signal is input to the input terminal CK (see FIG. 5 (b)).

As a result, the output terminal Q0 of the light-receiving shift register 23a becomes "H" level (see FIG. 5C), and 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 emitted from the LED 3a is set to a standby state that can be detected by the PD 13a. (2) Sync signal detection The microcomputer 5 of the projector 1 outputs a burst signal for synchronization to the other input terminal of each of the AND circuits 11a to 11h (see FIG. 4A). As a result, 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, when the PD 13a receives the light for synchronization detection projected on the detection area 8 by the LED 3a, the light reception signal is input to the waveform shaping circuit 18c via the conversion circuit 21a and the analog switch 22a. To be done. 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.

With this, the microcomputer 15 receives the synchronization detection signal, judges the signal, and if the signal has a predetermined length, it should perform a predetermined detection operation described below at a predetermined timing. The control signal is output to the light receiving circuit 14. (3) Detecting operation of ambient light In the projector 1, the microcomputer 5 is kept in a state where it does not output a signal for a fixed period after outputting a 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-described fixed period in which light is not projected by the light projector 1. That is, the microcomputer 15 supplies seven clock signals continuous at short intervals to the clock output terminals CK of the light receiving shift registers 23a to 23h.

In the light-receiving 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 (FIG. 5 (c)). ~ (J)). As a result, the conductive state of the analog switch 22a 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 supplied to the detection circuit 18.

Since the light is not being 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, light from a light source other than the light emitting device 1 is detected. Light, that is, ambient light is detected. When the disturbance light is detected in this way, the microcomputer 15 gives a blinking signal to the red LED 20a of the display circuit 20 and outputs an "H" level signal to the alarm output circuit 19b to indicate "disturbance". The "light detection state" is notified.

The notification of the “disturbance light detection state” is performed when the detection frequency is low, that is, when it is detected even once even in a short time. Furthermore, the “disturbance light detection state” continues for 6 μsec or more, for example. Alternatively, 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 an object, so that it works on the safe side. In addition, 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-shielded 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. 4). At the same time, the clock signal is sequentially output to the light projecting shift registers 12a to 12h between the pulses of the pulse signal (see FIG. 4C). As a result, first, the light emitting shift register 12a is at the "H" level in the initial state (see FIG. 4D), so that the LED 3a is turned on during the period when the pulse signal is applied to the AND circuit 11a. It

On the other hand, in the light receiver 2, the microcomputer 15 outputs a signal of “H” level to the data input terminal D of the light receiving shift register 23a, and also receives the clock input terminals CK of the light receiving shift registers 23a to 23h. The pulse train is output at a predetermined time interval.

As a result, an “H” level signal is output from the output terminal Q0 of the light-receiving 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 its optical axis is not shielded by the intrusion of an object, the light emitted from the LED 3a is detected by the PD 13a, and the microcomputer 15 receives the "H" level light through the light shielding detection circuit 18a. A signal indicating the light condition is output.

When an object enters and blocks the light emitted from the LED 3a, the light receiving signal is not output, and the microcomputer 15 stores that the light blocking is detected once. Then, when the detection of the light blocking is repeated twice or more, the microcomputer 15 judges that the light is in the “light blocking state”, lights the red LED 20a of the display circuit 20, and gives an output signal to the output circuit 19a. Is becoming

After that, the respective pairs of the LEDs 3b to 3h and the PDs 13b to 13h are 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 Operating State of Shift Register In the projector 1, the microcomputer 5 determines whether the operating states of the projecting shift registers 12a to 12h are normal based on the output signal from the output terminal Q7 of the projecting shift register 12h. To detect.

That is, if the light emitting shift registers 12a to 12h are operating normally, the output terminal Q7 of the light emitting shift register 12h outputs a signal as shown in FIG. 4 (K) to the microcomputer 5. It should be done. The output pattern in the normal operation is stored in advance in the microcomputer 5, and when the signal from the light emitting shift register 12h does not match the output pattern, one of the light emitting shift registers 12a to 12h fails. It is determined that the light emission has occurred, 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 “H” level signal is still output to the output terminal due to the failure of any of the light emitting shift registers 12 a to 12 h, or the output signal is not shifted. The occurrence of the malfunction of can be notified. In addition, 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 energizing current value during lighting is within a certain range, and The comparator should have output signals of "H" level and "L" level, respectively.

The microcomputer 5 determines that the detection signals from the current detection circuit 7 are “H” level and “L” level when the LEDs 3 a to 3 h are energized and turned on. In all other cases, it is determined that the "abnormal state" and the blinking signal is output to the LED 9a of the display circuit 9 and all the light projecting operations are stopped.

As a result, any one of the light emitting shift registers 12a to 12h, the AND circuits 11a to 11h, or the driving circuits 10a to 10h fails, and two or more LEDs 3a to 3h are lit at the same time, or one LED is lit. It is possible to promptly detect and notify the state where the light is not turned on. In addition, all the light projecting operations are stopped (when two or more lights 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 safety side. Then, this light emission stop state is locked and maintained until the power is turned off. (6) Detection operation of light receiving state a. Light Incident (Received) Level Detection In the light receiver 2, the light received signals from the PDs 13a to 13h are also input to the stable light incident detection circuit 18b. Then, as described above, the stable detection level of the stable incident light detection circuit 18b is set to a level higher than the detection level of the light shielding detection circuit 18a.

The stable incident light detection circuit 18b compares the level of the received light signal with the stable detection level when the received light signal is given, and when the level of the received light signal from the PDs 13a to 13h exceeds the stable detection level, the microcomputer A detection signal indicating "stable light input state" is output to 15. In response to this, the microcomputer 15 outputs a lighting signal to the green LED 20c of the display circuit 20 when the detection signal indicating the "stable light incident state" is received from all the PDs 13a to 13h. "Stable incident light state" is notified, and a feedback signal for hysteresis is given to the stable incident light detection circuit 18b.

On the other hand, an unstable light input state, for example, the optical axis is deviated, or the window 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, if the light entering state into the PDs 13a to 13h is unstable, even if the received signal exceeds the detection level of the light shielding detection circuit 18a, it exceeds the stable detection level of the stable light entering detection circuit 18b. Otherwise, the microcomputer 15 determines that it is in the “unstable light incident state”.

At this time, the microcomputer 15 first outputs a lighting signal to the yellow LED 20b of the display circuit 20 to display the “unstable light entering state”. Then, when this "unstable light input state" is continuously detected for, for example, 5 seconds, the microcomputer 15 outputs a blinking signal to the yellow LED 20b and gives an output signal to the alarm output circuit 19b to notify the user. To do.

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

That is, if the light receiving shift registers 23a to 23h are operating normally, the output terminal Q7 of the light receiving shift register 23h should output a signal as shown in FIG. 5 (j) to the microcomputer 15. Is. The output pattern at the time of normal operation is stored in advance in the microcomputer 15, and when the signal from the light receiving shift register 23h does not match the output pattern, any one of the light receiving shift registers 23a to 23h has a failure. Judge that it is occurring. Then, the micro computer 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 indicate that it is in the "abnormal state". Make a notification.

As a result, a failure of any of the light-receiving shift registers 23a to 23h may cause an “H” level signal to remain output to the output terminal, or the output signal may not be shifted. The occurrence of malfunction can be notified. In addition, by making the detection output the same as the light blocking state due to the entry 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, as shown in FIG. 5B, the microcomputer 15 outputs the output voltage of the analog switch 22h at a predetermined timing when the light receiving operation is not performed, that is, when the analog switch 22h is in the ON state and the OFF state. The judgment is made according to the output signal from the line check circuit 17 detected at the point.

The microcomputer 15 determines that it is operating normally when the output signal from the line check circuit 17 is inverted from the “H” level to the “L” level by the detection of the above two points, and otherwise In this case, it is determined that the output line to the detection circuit 18 is broken, or one of the analog switches 22a to 22h remains in the ON state, or the like, which is an "abnormal state". When the microcomputer 15 judges 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, if a failure occurs in any of the line to the detection circuit 18, the light receiving shift registers 23a to 12h, the analog switches 22a to 22h, or the conversion circuits 21a to 21h, it can be quickly detected. Can be notified. In addition, by making the detection output the same as the light blocking state due to the entry 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 of the various detection operations described above are summarized as shown in Tables 1 and 2 when corresponding 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, the current detection circuit 7 detects the load currents that sequentially flow through the LEDs 3a to 3h, and the microcomputer 5 has a load current value within a certain range, that is, a load current range for one LED. Since it is determined whether or not it is inside, when abnormal conditions such as two or more lighting at the same time occur, this condition can be detected promptly, and therefore light can be shielded with a simple configuration. The reliability of the state detection operation can be improved.

In the above embodiment, the disturbance light is detected with a certain period of time for collectively detecting the PDs 13a to 13h, but the invention is not limited to this, and 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.

Further, in the above embodiment, the alarm output circuit 19b is provided, but the present invention is not limited to this, and it is also possible to use an indicator lamp or the like instead of the alarm output.

Further, in the above embodiment, the case where the present invention is applied to the area sensor having eight optical axes is described, but the present invention is not limited to this, and a plurality of pairs of a light emitting element and a light receiving element forming the optical axis are provided. It can be applied to anything in general.

[0065]

[Effect of the device]

 As described above, according to the multi-optical axis photoelectric switch of the present invention, the load current supplied to the plurality of light projecting elements is detected by the current detection means, and the detected load current is detected in the predetermined range by the state detection means. Since multiple light emitting elements are not turned on sequentially at a predetermined timing, the detected load current value deviates from the predetermined range, and This has an excellent effect that an abnormal state such as a light state can be detected quickly, and thus the reliability of the light-shielded state detection operation can be improved with a simple configuration.

[Brief description of drawings]

FIG. 1 is an electrical configuration diagram of a projector showing an embodiment of the present invention.

FIG. 2 is an electrical configuration diagram of a light receiver.

FIG. 3 is a block diagram of the overall configuration

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 (state detecting means), 7 is a current detecting circuit (current detecting means), and 8 is Detection area, 9 is a display circuit, 11a to 11
h is an AND circuit, 12a to 12h are shift registers,
13a to 13h are photodiodes (light receiving elements), 1
4 is a light receiving circuit, 15 is a microcomputer (control means), 17 is a line check circuit, 18 is a detection circuit (judgment means), 18a is a light shielding detection circuit, 18b is a stable light detection circuit, 18c is a waveform shaping circuit, 19 Is an output circuit, 19a
Is a detection output circuit, 19b is an alarm output circuit, 20 is a display circuit, 20a is a red LED, 20b is a yellow LED, and 20c.
Is a green LED, 22a to 22h are analog switches,
Reference numerals 23a to 23h are shift registers.

Claims (1)

[Scope of utility model registration request] 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 shielding state in the detection area based on the light receiving signal from the light receiving element, current detecting means for detecting the load current supplied to the plurality of light projecting elements, and current detected by the current detecting means A multi-optical axis photoelectric switch comprising: a state detection unit that determines whether or not a value is within a predetermined range.