JP2002350229A - Photoelectric sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a photoelectric sensor capable of mutually preventing false detection of discriminating light in the case of arranging a plurality of sensors side by side. SOLUTION: Multi-optical axis photoelectric sensors 1 to 3 are formed by projectors 1a to 3a and light receiving means 1b to 3b including one or more pairs of LED 4a to 4d and PD 10a to 10d disposed opposite to each other to form an optical axis for detecting an object. In this arrangement, in the case of arranging three multi-optical axis photoelectric sensors 1 to 3 side by side to widen a detecting area 11, in the respective projectors 1a to 3a, discriminating light emitting time for emitting light of the LED 4a emitting discriminating light is set to a value not matching the sum of the discriminating light emission time of the others. In the respective light detecting devices 1b to 3b, the discriminating light receiving time is set corresponding to the discriminating light emitting time set in each of the projectors 1a to 3a making a pair.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photoelectric sensor for detecting an object by transmitting and receiving an optical signal between a light projecting element and a light receiving element forming a pair.

[0002]

2. Description of the Related Art Conventionally, a photoelectric sensor, for example, a transmission-type, light-synchronous multi-optical axis photoelectric sensor, includes a light projecting device having a plurality of light projecting elements and a plurality of light receiving elements forming a pair with the light projecting device. The light receiving device is arranged independently so as to face the light receiving device. Then, by detecting a light blocking state of a plurality of optical axes formed between each light projecting element and the light receiving element, detection of an intrusion of an object in a predetermined detection area is performed.

In this multi-optical axis photoelectric sensor, acquisition of synchronization between the light projecting device and the light receiving device by an optical synchronization method is performed as follows. First, the light-emitting device includes a light-emitting time of a light-emitting element (hereinafter, referred to as an identification light-emitting element) that emits light at the start of a light-emission cycle in which light emission of all the light-emitting elements makes one cycle (hereinafter, an identification light-emitting time is referred to as an identification light-emitting time). ) And light emission timing for sequentially emitting light from each light emitting element are set in advance. Further, the light receiving device has a light receiving time (hereinafter, referred to as an identification light receiving element) of a light receiving element (hereinafter, referred to as an identification light receiving element) paired with the identification light emitting element so as to have a value substantially equal to the identification light emitting time. Is set in advance.

Next, at the start of the light emitting cycle, only the output of the light receiving element for identification is enabled in the light receiving device, and the light emitting device causes the light emitting element for identification to emit light for the light emission time for identification. As a result, an optical signal (hereinafter, referred to as identification light) is emitted. Subsequently, in the light receiving device, the identification light is detected as a light receiving signal by the identification light receiving element, and synchronization with the light emitting device is performed when the detection time obtained by measuring the detected light receiving signal matches the identification light receiving time. Can be

[0005] When the synchronization between the light emitting device and the light receiving device is obtained in this way, the light emitting device sequentially transmits an optical signal (hereinafter, referred to as detection light) from each light emitting element in accordance with the light emitting timing. In the light-receiving device, only the output of the light-receiving element paired with the light-emitting light-emitting element is sequentially enabled in synchronization with the light-emitting timing, and the detection of the light-receiving signal output from the enabled light-receiving element is performed. Done. Then, by detecting the light-shielded state of each optical axis, the intrusion of an object in the detection area is detected.

In this multi-optical axis photoelectric sensor, only the output of the light receiving element paired with the light emitting element that emits light is enabled because a plurality of light emitting elements and light receiving elements are adjacent to each other at a short distance. For example, when an object enters a predetermined optical axis and the optical axis is interrupted, the light is emitted from the light emitting element of the optical axis adjacent to the light receiving element of the interrupted optical axis. This is to prevent the detected light from entering and being regarded as being in the light incident state, so that the intrusion of an object can be reliably detected at each optical axis.

[0007]

By the way, this multi-optical axis photoelectric sensor is provided by arranging a plurality of sensors in parallel.
It is also used for expanding the detection area. However, when a plurality of light emitting devices are arranged side by side, the identification light emitted from the identification light emitting device of the predetermined light emitting device is arranged not only in the identification light receiving device of the light receiving device forming a pair with the identification light emitting device but also in parallel. There is a possibility that the light may enter the identification light receiving element of the light receiving device. For this reason, the light emission time for identification of each light emitting device is set to be different from each other, and the light receiving time for identification of each light receiving device forming a pair with each light emitting device is also set to be different from each other in accordance with the light emitting time. This prevents erroneous synchronization due to erroneous detection of the identification light between the multi-optical axis photoelectric sensors, in which the identification light emitted from another light emitting device is synchronized with its own light receiving device.

FIGS. 4 (a) to 4 (c) show, for example, each of the light projecting devices in the case where three sets of multi-optical axis photoelectric sensors composed of four pairs of light projecting elements and light receiving elements are arranged in parallel. FIG. 4 is a timing chart showing the light projection timing of an emitted optical signal. As shown in FIGS. 4A to 4C, the light emission time for identification of each identification light is set to a ratio of “3: 2: 1”. This prevents erroneous detection of the identification light between them.

However, the multi-optical axis photoelectric sensors arranged side by side operate asynchronously, and each projection sensor is operated due to an individual difference of an oscillation circuit for generating a reference clock for operating each projection device. Since a slight shift occurs in the time width of the light cycle, the phase relationship of each light emission cycle always fluctuates. For this reason, when the phase relations of the optical signals whose ratios are set to “2” and “1” approach each other so as not to overlap as shown in FIGS. Are synthesized, and a synthesized light equivalent to the optical signal whose ratio is set to “3” as shown in FIG. 4F is formed.

At this time, if the multi-optical axis photoelectric sensor whose ratio is set to "3" is in the state at the start of the light emission cycle (light receiving standby state), the multi-optical axis photoelectric sensor Synthesized light having a ratio of “3” enters the identification light receiving element, and erroneous synchronization occurs due to erroneous detection of the identification light. Then, once an erroneous synchronization occurs, the multi-optical axis photoelectric sensor will not be able to achieve normal synchronization between the light emitting device and the light receiving device until the ratio of the combined light is no longer “3”. However, there has been a problem that the intrusion of an object into the detection area cannot be accurately detected.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a photoelectric sensor capable of preventing erroneous detection of identification light from each other when a plurality of devices are juxtaposed. It is in.

[0012]

According to a first aspect of the present invention, there is provided a photoelectric sensor comprising: a plurality of light emitting elements and a plurality of light receiving elements provided in pairs so as to form an optical axis for detecting an object; Based on the emission time for identification to cause the elements to emit light at the start of the light emission cycle and the emission time for detection to cause each of the light emission elements to emit light sequentially thereafter, the light emission elements are repeatedly emitted at a predetermined light emission timing in the adjacent order. The light-emitting circuit to be paired with the one light-emitting element, and the light-receiving time corresponding to the identification light-emitting time until the light-receiving element, whose output has been previously enabled, is in a light-receiving state and becomes a non-light-receiving state, corresponds to the identification light-emitting time. Each time the light receiving time coincides with a predetermined identification light receiving time, an enabling means for enabling an output of a light receiving element forming a pair of each of the light emitting elements in synchronization with the light emitting timing, and an output from the enabled light receiving element. Detecting the received light signal A light-shielding state detecting means for detecting a light-shielding state of the optical axis for detecting the object. It is characterized in that the value is set to a value that does not match the sum of the light emission times for identification of the sensor. According to such a configuration, when a plurality of photoelectric sensors are juxtaposed in order to widen a detection area for detecting an intrusion of an object, one light emitting element of each light emitting circuit is set to each. When the light is emitted so as to be continuously switched based on the identification light emission time, even if the apparent light emission time is prolonged due to the combined light of the optical signals, the combined light is output by the identification means of each of the validating means. It is possible to prevent the synchronization with the time, and it is possible to prevent occurrence of erroneous synchronization due to erroneous detection of the identification light in which the synchronizing light synchronizes the respective activating means.

According to a second aspect of the present invention, in the photoelectric sensor, a pair of a light emitting element and a light receiving element provided so as to form an optical axis for detecting an object, and the light emitting element is determined based on a light emission time for identification. A light emitting circuit that repeatedly emits light at the light emitting timing, and a predetermined light receiving time corresponding to the identification light emitting time until the light receiving element whose output is always enabled is in a light receiving state and then becomes a non-light receiving state. A light-shielding state detecting means for detecting a light-shielding state of the optical axis for object detection based on determining whether the light-receiving time coincides with the light-receiving time for identification. The light emission time is set to a value that does not match the sum of the light emission times for identification of a plurality of other photoelectric sensors arranged in parallel. According to such a configuration, in the case where a plurality of photoelectric sensors are arranged in parallel, the light emitting elements of each light emitting circuit emit light so as to be continuously switched based on the identification light emitting time set for each of the light emitting elements. However, the apparent light emission time is prolonged by the combined light of these optical signals, but since the combined light does not coincide with the identification light receiving time of each light blocking state detecting means, the identification light is erroneously detected by the combined light. Can be prevented.

According to a third aspect of the present invention, in the photoelectric sensor, the light emitting circuit includes a power-of-two ratio in which the light emission time for identification is different from the light emission time for identification set in another photoelectric sensor arranged in parallel. Are set so as to satisfy the following relationship. According to such a configuration, it is possible to use the relationship of the power-of-two ratio so that the light emission time for identification of a predetermined light receiving device does not match the sum of the light emission times for identification of other light receiving devices. Easy.

According to a fourth aspect of the present invention, in the photoelectric sensor, the light emitting circuit is configured to be capable of selectively setting a plurality of light emission times for identification. According to such a configuration, the emission time for identification can be easily set in the light emitting circuit. Accordingly, in a case where a plurality of photoelectric sensors are juxtaposed, it is possible to easily set the identification light emission time of each light emitting circuit to be different from each other.

According to a fifth aspect of the present invention, in the photoelectric sensor, the validating means is configured to be able to selectively set a plurality of identification light receiving times corresponding to the plurality of identification light emission times. . According to such a configuration, the light receiving time for identification can be easily set in the validation means. Thus, in an application in which a plurality of photoelectric sensors are arranged side by side, each of the activating means can easily set the identification light receiving time corresponding to the identification light emission time set in the light emitting circuit forming a pair with itself. it can.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the photoelectric sensor of the present invention is applied to a transmissive, light-synchronous, multi-optical axis photoelectric sensor will be described below with reference to FIGS.

First, FIG. 2 shows an arrangement example in which, for example, three sets of multi-optical axis photoelectric sensors 1 to 3 are juxtaposed in order to widen a detection area 11 for detecting the intrusion of an object. is there. As shown in FIG. 2, the multi-optical axis photoelectric sensors 1 to 3 are independently arranged so that the light emitting devices 1a to 3a and the light receiving devices 1b to 3b, which are light emitting circuits, face each other. I have. Further, since the multi-optical axis photoelectric sensors 1 to 3 are juxtaposed at a short distance, the optical signals emitted from each of the light projecting devices 1a to 3a spread at a predetermined spread angle. Light receiving devices 1b to 1c
Is to be irradiated.

FIG. 1 shows an electric block configuration of the multi-optical axis photoelectric sensor 1. Since the configurations of the multi-optical axis photoelectric sensors 1 to 3 are the same, the configuration of the light projecting device 1a and the light receiving device 1b will be described below using one multi-optical axis photoelectric sensor 1 as an example.

[Explanation of the structure of the light projecting device 1a]
The light emitting side CP for driving and controlling the LEDs 4a to 4d (the LED 4a corresponds to one light emitting element) as light emitting elements
U (central processing unit) 5 is built in,
The LED selection terminal provided on the light emitting side CPU 5 is connected to the input terminal of the shift register 6, and the light emitting signal output terminal is connected to one of the input terminals of the AND circuits 7a to 7d.

The output terminal of the ratio setting circuit 8 is connected to the ratio setting terminal provided on the light emitting side CPU 5. The ratio setting circuit 8 includes three resistors 8a to 8c having one end pulled up to a high level and the other end connected to the output terminal, and one end of one of the resistors 8a to 8c on the output terminal side. Is switched to a low level by a switch 8d. By switching the switch 8d, three different types of light emitting signals T1 are provided.
To T3 (see FIG. 3 described later) can be selected.

The four output terminals of the shift register 6
It is connected to the other input terminals of the ND circuits 7a to 7d. Output terminals of the AND circuits 7a to 7d are connected to input terminals of the LED driving circuits 9a to 9d, and output terminals of the LED driving circuits 9a to 9d are connected to input terminals of the LEDs 4a to 4d. And these light emitting CPUs
5, ratio setting circuit 8, shift register 6, AND circuit 7
a to 7d, LED driving circuits 9a to 9d and LED4
The light projecting device 1a is constituted by a to 4d.

[Description of Structure of Light Receiving Device 1b] Light Receiving Device 1b
Is provided with PDs 10a to 10d as four light receiving elements paired with the LEDs 4a to 4d.
a and the light receiving device 1b are arranged so as to face each other, so that the LEDs 4a to 4d and the PDs 10a to 1
Optical axes 11a to 11d for object detection are formed between 0d. The optical axes 11a to 11d form a detection area 11 for detecting entry of an object.

The output terminals of the PDs 10a to 10d are connected to the input terminals of the light receiving amplifiers 12a to 12d. Output terminals of the light receiving amplifiers 12a to 12d are connected to input terminals of analog switches 13a to 13d whose input and output are turned on and off by a control signal given to the control terminal. The output terminals of the analog switches 13a to 13d are commonly connected, and are connected to the input terminal of a comparator 14 for comparing the magnitude with a predetermined reference voltage. The output terminal of the comparator 14 is connected to a light receiving signal detection terminal provided in the light receiving CPU 15 for electrically controlling the entire light receiving device 1b, and is also connected to an input terminal of the off delay circuit 16. An output terminal of the off-delay circuit 16 is connected to a synchronization detection terminal provided in the light receiving CPU 15.

The PD selection terminal provided in the light receiving CPU 15 is connected to the input terminal of the shift register 17, and the four output terminals of the shift register 17 are connected to the control terminals of the analog switches 13a to 13d.

The output terminal of the ratio setting circuit 18 is connected to the ratio setting terminal provided in the light receiving CPU 15. The ratio setting circuit 18 includes resistors 18a to 18c and a switch 18d, similarly to the ratio setting circuit 8 provided in the light emitting device 1a. The light receiving CPU 15 has a light shielding state detecting function 1 as a light shielding state detecting means for detecting the light shielding state of each of the optical axes 11a to 11d (that is, the intrusion of an object in the detection area 11).
9 is provided, and the result detected by the light-shielding state detection function 19 is output to the output circuit 20.

Although not shown, the output circuit 20 is used for, for example, turning on / off an external indicator based on the detection result, or converting the detection result into a predetermined format and outputting it to an external device. Used. The analog switches 13a to 13d, the shift register 17, the light receiving CPU 15, and the ratio setting circuit 18 constitute an enabling circuit 21 as an enabling means.
The light receiving device 1b includes the light receiving amplifiers 0a to 10d, the light receiving amplifiers 12a to 12d, the enabling circuit 21, the comparator 14, the off-delay circuit 16, and the output circuit 20.

[Explanation of operation of light projecting device 1a] Next, the operation of the light projecting devices 1a to 3a will be described.
Will be described below as an example. Each of the LEDs 4a to 4d provided in the light emitting device 1a emits an optical signal across a detection area 11 for detecting an intrusion of an object. An optical signal (hereinafter, referred to as identification light) emitted from the LED 4a is used for detecting an object and used for synchronization with the light receiving device 1b. Light signals emitted from the LEDs 4b to 4d (hereinafter, referred to as detection light) are used only for detecting an object.

The light emitting side CPU 5 operates based on a reference clock output from an oscillation circuit (not shown), and reads out a light emitting control program written in a ROM (not shown) to thereby electrically control the entire light emitting device 1a. It is supposed to do.

In the light emitting side CPU 5, a ratio setting circuit 8
By switching the switch 8d, three types of light emission signals T1 to T3 shown in FIGS. 3A to 3C can be selectively output. These light emission signals T1 to T3
, The light emission cycle is set equal, and the light emission signal PS0 for emitting the identification light from the LED 4a and the light emission signals PS1 to PS3 for emitting the detection light from the other LEDs 4b to 4d. Are set to be output at different predetermined light emission timings within one light emission cycle. Note that the detection light emission signals PS1 to PS3 are generated in a pulse shape, and the identification light emission signal PS0 has a sufficiently long output period as compared with the detection light emission signals PS1 to PS3. Is generated in the form of a burst repeating on and off.

The output time of the light emitting signal PS0 for identification is set to a ratio of "4: 2: 1" having a power ratio of 2 in the order of the light emitting signals T1 to T3. , The light emission time of the LED 4a, that is, the light emission time for identification is determined. In each of the light emitting devices 1a to 1c, the ratio of the light emission time for identification is set to be different from each other, so that the light emission time for identification does not match the sum of the output times of the other light emission devices. .

The selected light emitting signals are simultaneously output to one of the input terminals of the AND circuits 7a to 7d. At this time, an LED selection signal of one pulse is output from the LED selection terminal of the light emitting side CPU 5 to the shift register 6, and the LED selection signal is synchronized with the light emission signal while being shifted by the shift register 6. Then, the data is sequentially output from each output terminal of the shift register 6. As a result, the identification light emission signal PS0 and the detection light emission signals PS1 to PS3 are transmitted to the LEDs via the AND circuits 7a to 7d.
The signals are sequentially output to the drive circuits 9a to 9d. The LEDs 4a and 4d sequentially emit light based on the light emission timing, whereby the identification light is emitted from the LED 4a and the detection light is emitted from the LEDs 4b to 4d.
A series of operations in which the LEDs 4a to 4d sequentially emit light are repeatedly performed according to a light emitting cycle that is continuously repeated at predetermined intervals.

[Explanation of the operation of the light receiving device 1b] Next, the operation of the light receiving devices 1b to 3b will be described.
Will be described below as an example. In the light receiving device 1b, in each light emitting cycle, first, the LED
By detecting the identification light with the PD 10a paired with the LED 4a, synchronization with the light emitting device 1a paired is established, and subsequently, the PDs 10b-10d paired with the LEDs 4b-4d.
By sequentially detecting the detection light at d, the detection area 1
The detection of the intrusion of the object in the inside 1 is performed. Hereinafter, the operation in one light emitting cycle will be described.

By switching the switch 18d of the ratio setting circuit 18, each of the light receiving devices 1b to 3b has a "4: 2: 1" ratio having a power ratio of 2 which is substantially equal to the light emission time for identification. The light receiving time for identification set to the ratio is configured to be selectable, and each light receiving device 1b to 3b has an LED set to the light emitting device 1a to 3a forming a pair.
The light receiving time for identification having the same ratio as the light emission time for identification in 4a is set in advance.

<Acquisition of Synchronization between Light Projecting Device 1a and Light Receiving Device 1b> At the start of a light projecting cycle in which the light projecting device 1a and the light receiving device 1b are not synchronized, the light receiving side C
In the PU 15, the analog switch 13a is connected so that only the input and output of the PD 10a paired with the LED 4a that emits the identification light is conducted (validated), and the input and output of the other PDs 10b to 10d are cut off (disabled). 13d to 13d.

In this state, when the burst identification light emitted from the LED 4a enters the PD 10a, the PD 10a
In a, the identification light is photoelectrically converted into a light reception signal and output. FIG. 3D is an example showing an output waveform of a light receiving signal when it is assumed that all the light signals emitted from the LEDs 4a to 4d enter the PD 10a, for example. As shown in FIG. 3D, the output waveform of the light receiving signal has a dull edge. And this light receiving signal is
Amplified by the light receiving amplifier 12a, the analog switch 13
The signal is output to the comparator 14 via a. (Note that, in practice, the analog switch 12a
Is cut off, the light receiving signal after the cutoff is not output to the comparator 14. The comparator 14 compares the amplified light reception signal with a predetermined reference voltage, and outputs a high level when the light reception signal is higher than the reference voltage, and outputs a low level otherwise. In this manner, the light receiving signal is shaped into a rectangular shape by the comparator 14 and is supplied to the light receiving side CPU 15 and the off delay circuit 16.

In the off delay circuit 16, the off timing of the light receiving signal from the comparator 14 is delayed by a predetermined time. FIG. 3E shows an output waveform when the light receiving signal of FIG. 3D is output from the off-delay circuit 16, and as shown in FIG. It is shaped into a pulsed rectangular wave.

In the light receiving side CPU 15, the PD based on the pulse width of the light receiving signal given from the off delay circuit 16 is used.
The light receiving time of the identification light at 10a (that is, the light receiving time from when the LED 4a is in the light receiving state to when the LED 4a is in the non-light receiving state) is measured, and it is determined whether or not it matches the set identification light receiving time. Will be Thereby, the light emitting device 1a forming a pair
And the other light projecting device 2a or 3a
Is discriminated as being emitted from. When the coincidence between the measured light receiving time and the light receiving time for identification is detected, synchronization with the identification light emitted from the LED 4a (that is, synchronization between the light emitting device 1a and the light receiving device 1b) is established. Be taken.

Subsequently, the light receiving side CPU 15 controls the shift register 17 so that the LEDs 4b to 4b
A control signal is generated to enable the outputs of the PDs 10b to 10d paired with the LEDs 4b to 4d while synchronizing the emission of the detection light by the d. FIGS. 3F to 3H show control signals C1 sequentially output from the output terminals of the shift register 17 when the light emission signals T1 to T3 of FIGS. 3A to 3C are synchronized. 3 shows the output timings of C3 to C3. As shown in FIGS. 3 (f) to 3 (h), the analog switches 13b to 13d are turned on in synchronization with the light emission of the LEDs 4b to 4d, so that the PD paired with the LEDs 4b to 4d.
Only the outputs of 10b to 10d are activated and the PD 10b
The light receiving signal output from the
Given to.

In the comparator 14, the same processing as that for the light receiving signal by the identification light is performed, and each light receiving signal shaped into a rectangle is sent to the light receiving side CPU 15 and the off-delay circuit 1.
6 is output. Subsequently, in the light receiving side CPU 15, the detected light receiving signal is counted by the light shielding state detecting function 19, and the counted value and the PD1 for receiving the detected light are counted.
The comparison with the number (three) of 0b to 10d is performed. When the count value and the number match, it is determined that no object has entered the detection area 11 based on the determination that all the optical axes 11a to 11d are not shielded. You. If the comparisons do not match, it is determined that an object has entered the detection area 11 based on the determination that the predetermined optical axis has been shielded.
Then, the determination result is output to the output circuit 20.
In the light-receiving side CPU 15, when it is determined that an object has entered the detection area 11 continuously for a predetermined number of times, the result of the determination that the object has entered is output to the output circuit 20.
Output to

In the light receiving device 1b, the presence or absence of an object entering the detection area 11 is also determined by the light receiving signal of the identification light. This is because, in the light emitting device 1a, the light emitting cycle is continuously repeated at a predetermined interval. Therefore, when the light receiving side CPU 15 does not detect the light receiving signal by the identification light only for a predetermined time, the light receiving side enters the detection area 11. Is determined by determining that an object has entered.

[Explanation of Operation of Asynchronous Operation of Each Multi-Optical-Axis Photoelectric Sensor 1 to 3] In the above configuration, each of the multi-optical-axis photoelectric sensors 1 to 3 arranged side by side operates asynchronously. Since the time width of each light emitting cycle slightly shifts due to individual differences in the oscillation circuit that generates the reference clock for operating each of the light emitting devices 1a to 3a, the phase relationship of each light emitting cycle is Constantly fluctuating. For this reason, when the phase relations of the light-projected signals T2 and T3 whose ratios are set to "2" and "1" are close enough that they do not overlap, for example, as shown in FIGS. 3 (i) and (j). The discriminating light based on the two light-projected signals T2 and T3 is combined to form a combined light equivalent to the discriminating light based on the light-projected signal T4 whose ratio is set to "3" as shown in FIG. You. However, each PD1 of each light receiving device 1b to 3b
Even if the combined light having the ratio of "3" is incident on 0a to 10a, there is no light-receiving device for which the ratio is set to "3" in the identification light receiving time of each of the light receiving devices 1b to 3b. The combined light does not cause erroneous synchronization between the multi-optical axis photoelectric sensors 1 to 3 due to erroneous detection of the identification light.

As described above, according to this embodiment, when the three photoelectric sensors 1 to 3 are juxtaposed in order to widen the detection area 11 for detecting the intrusion of an object, a predetermined light emission is required. Since the light emission time for identification of each of the light emitting devices 1a to 3a is set so that the light emission time for identification of the device is different from the sum of the light emission times for identification of the other light emitting devices,
For example, LEDs 4a and 4 of two light emitting devices 2a and 3a
If a emits light so as to be continuously switched based on the identification light emission time set for each of them, even if the apparent light emission time becomes longer due to the combined light of the identification light, the combined light is transmitted to the light receiving device. 1b does not coincide with the light receiving time for identification.
It is possible to prevent the occurrence of erroneous synchronization due to erroneous detection of the identification light that would cause the synchronization of b. That is, each of the photoelectric sensors 1 to 3 can prevent erroneous detection of identification light in which its own light receiving device is synchronized with the combined light of identification light emitted from the plurality of light projecting devices.

In each of the light emitting devices 1a to 3a, a ratio having a different power-of-two ratio to the light emission time for identification set to another light emitting device arranged in parallel (“4:
2: 1 ”), the self-identifying light emission time is set so as to make it easy to identify other light emitting devices by utilizing the relationship of the power-of-two ratio. It can be made to be inconsistent with the sum of the light emission times for use.

Further, since the light emitting devices 1a to 3a are configured such that a plurality of light emission times for identification can be selectively set by the ratio adjusting circuit 8, only the switch 8d of the ratio adjusting circuit 8 is switched. The light emission time for identification can be easily set. Thus, even when the three photoelectric sensors 1 to 3 are arranged in parallel, it is possible to easily set the light emission time for identification of each of the light emitting devices 1a to 3a to be different from each other.

Further, the light receiving devices 1b to 3b are configured so that the ratio adjusting circuit 18 can selectively set the identification light receiving time at a ratio corresponding to the identification light emission time of the light emitting devices 1a to 3a forming a pair. Accordingly, the identification light receiving time can be easily set only by switching the switch 18d of the ratio adjusting circuit 18. Thereby, in each of the light receiving devices 1b to 3b, even when the three photoelectric sensors 1 to 3 are arranged side by side, the identification corresponding to the identification light emission time set in the light emitting devices 1a to 3a forming a pair with itself. Light receiving time can be easily set.

The present invention is not limited to the embodiment described above and shown in the drawings.
Extension is possible. In one embodiment of the present invention, the photoelectric sensor is applied to a multi-optical axis photoelectric sensor having a plurality of pairs of light projecting elements and light receiving elements. However, the present invention is not limited to this. May be applied to a single optical axis photoelectric sensor having For example, the single optical axis photoelectric sensor may be constituted by a pair of a light emitting element and a light receiving element, a light emitting circuit, and a light shielding state detecting means provided so as to form an optical axis for object detection. In this case, the light emitting circuit causes the light emitting element to repeatedly emit light at a predetermined light emitting timing based on the light emission time for identification, and the light shielding state detecting means sets the light receiving element whose output is always enabled to the light receiving state. The light-blocking state of the object-detecting optical axis is detected based on determining whether the light-receiving time until the light-receiving state becomes the same as the predetermined light-receiving time for identification corresponding to the light-emitting time for identification. To do it. Then, in an application in which a plurality of single optical axis photoelectric sensors are juxtaposed, the discriminating light emitting time of a predetermined light emitting circuit is set to a value that does not match the sum of the discriminating light emitting times of the other plural light emitting circuits arranged in parallel. Set to. Accordingly, when the light emitting elements of each light emitting circuit emit light so as to be continuously switched based on the identification light emitting time set for each of the light emitting circuits, the apparent light emitting time due to the combined light of those optical signals is Although the length of the combined light is longer, the combined light does not coincide with the identification light receiving time of each of the light-shielded state detecting means, so that erroneous detection of the identification light by the combined light can be prevented.

In one embodiment of the present invention, an optical signal emitted from one of the light projecting elements is used for obtaining synchronization between the light projecting circuit and the activating means and for detecting an object. However, the present invention is not limited to this, and may be used, for example, only for obtaining synchronization between the light emitting circuit and the activating means. Further, an optical signal is emitted from one light emitting element in the order of the synchronization light and the detection light, so that synchronization between the light emitting circuit and the activating means is acquired by the synchronization light, and the object is detected by the detection light. It may be.

[0049]

As is apparent from the above description, in the photoelectric sensor of the present invention, when a plurality of photoelectric sensors are juxtaposed, the light emission time for identification of a predetermined light emitting circuit is different from that of another light emitting circuit. Since the light emission time for identification of each light emitting circuit is set so as to be a value inconsistent with the sum of the light emission time for identification of When the light is emitted so as to be continuously switched based on the above, even if the apparent light emission time is lengthened by the combined light of the optical signals, the combined light does not coincide with the identification light receiving time of each of the activating means. This makes it possible to prevent the occurrence of erroneous synchronization due to erroneous detection of the identification light in which the synchronizing light synchronizes the respective validating means.

[Brief description of the drawings]

FIG. 1 is an electric block diagram of a photoelectric sensor showing one embodiment of the present invention.

FIG. 2 is an arrangement diagram when three photoelectric sensors are arranged side by side;

FIG. 3 is a timing chart of each signal indicating the operation of the photoelectric sensor.

FIG. 4 is a light emission timing chart of a light emission circuit showing a conventional example.

[Explanation of symbols]

In the drawings, 1 to 3 are multi-optical axis photoelectric sensors (photoelectric sensors), 1
a to 3a are light emitting devices (light emitting circuits), 1b to 3b are light receiving devices, 4a to 4d are LEDs (light emitting devices), 8, 18 are ratio adjusting circuits, 10a to 10d are PDs (light receiving devices), 11a
11 to 11d are optical axes, 11 is a detection area, 19 is a light-shielded state detection function (light-shielded state detection means), and 21 is an activation circuit (validation means).

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2G065 AA04 AB28 BA09 BA33 BC14 BC22 BC35 BD01 DA15 5F089 BA02 BC07 BC15 BC22 BC23 BC29 CA21 FA03 FA06 GA01 5J050 AA13 BB22 CC00 DD18 EE03 EE17 EE31 EE35 EE39 FF04 FF10

Claims (5)

[Claims] 1. A plurality of light emitting elements and light receiving elements provided in pairs to form an optical axis for object detection, and identification for causing one light emitting element to emit light at the start of a light emitting cycle. A light emitting circuit that repeatedly emits light at predetermined light emission timing in the order of adjacent light emitting elements based on a light emitting time for use and a light emitting time for detection for sequentially emitting light from each light emitting element, and the one light emitting element; Each time a light receiving time until a non-light receiving state after a light receiving element in which a pair of light emitting elements whose outputs are previously enabled is in a light receiving state matches a predetermined identification light receiving time corresponding to the identification light emitting time, Enabling means for enabling an output of a light receiving element that is a pair of each of the light emitting elements in synchronization with the light emitting timing; and detecting the light receiving signal output from the enabled light receiving element. Check the light blocking state of the detection optical axis. A light-shielding state detecting unit that emits light, wherein the light emitting circuit has a value that does not match the sum of the light emission times for identification of the other plurality of photoelectric sensors in which the light emission times for identification are juxtaposed. A photoelectric sensor characterized by being set. 2. A pair of light emitting element and light receiving element provided so as to form an optical axis for object detection, and said light emitting element is repeatedly emitted at a predetermined light emission timing based on an emission time for identification. A light emitting circuit for causing the light receiving element, whose output is always enabled, to enter a non-light receiving state after the light receiving element enters a non-light receiving state coincides with a predetermined identification light receiving time corresponding to the identification light emitting time A light-shielding state detecting means for detecting a light-shielding state of the optical axis for object detection based on the determination. The photoelectric sensor is set to a value that does not match the sum of the light emission times for identification of a plurality of other photoelectric sensors. 3. The light emitting circuit sets the light emission time for identification so as to have a different power-of-two relationship with respect to the light emission time for identification set for another photoelectric sensor arranged in parallel. The photoelectric sensor according to claim 1, wherein: 4. The photoelectric sensor according to claim 1, wherein the light emitting circuit is configured to be capable of selectively setting a plurality of identification light emission times. 5. The photoelectric sensor according to claim 4, wherein the validating means is configured to be able to selectively set a plurality of identification light receiving times corresponding to the plurality of identification light emission times. .