JP4278567B2 - Multi-axis photoelectric sensor - Google Patents

Description

  The present invention relates to a multi-optical axis photoelectric sensor.

  Conventionally, as a multi-optical axis photoelectric sensor, there is one in which a light projector provided with a plurality of light projecting elements and a light receiver equipped with a plurality of light receiving elements corresponding to each light projecting element are arranged to face each other. .

  The light projecting element provided in the light projector repeatedly performs the light projecting scanning operation in which light is projected sequentially at a predetermined light projecting timing at a predetermined cycle, and based on the light receiving signal from the light receiving element corresponding to each light projecting element. Thus, an object intrusion into the detection area is detected.

  By the way, as shown in FIG. 6, in order to detect intrusion of an object in a wider area, a plurality of multi-optical axis photoelectric sensors 41 and 42 may be installed, and the multi-optical axis photoelectric sensors 41 and 42 are close to each other. May be placed in a state.

  In this case, for example, when the light projecting / receiving operation is performed on any one of the optical axes of the multi-optical axis photoelectric sensor 41 installed above, the light is projected from the multi-optical axis photoelectric sensor 42 installed below. Light may enter the light receiving element performing the light receiving operation of the upper multi-optical axis photoelectric sensor 41 as interference light. Then, although the optical axis of the upper multi-optical axis photoelectric sensor 41 is shielded from light, a false detection that the light shielding state of the optical axis cannot be detected occurs.

Therefore, in order to prevent such erroneous detection, interference light is detected by the light receiving element immediately before the timing of detection of light shielding by the light receiving element. It is conceivable that the detection scan operation is performed again at a predetermined cycle and the erroneous detection due to interference light from other multi-optical axis photoelectric sensors 42 is prevented.
JP 2003-133933 A

  By the way, as the interference light incident on the light receiving element, in addition to the interference light from the other multi-optical axis photoelectric sensor 42 as described above, other light sources (for example, a single optical axis photoelectric sensor, a lamp, etc.). There is no interference light.

  On the other hand, in the above configuration, the interference light caused by these different factors is not discriminated. When the interference light is detected for a specific light receiving element, erroneous detection is prevented by changing the period of the subsequent light projection scanning operation. It was a configuration.

  Here, when the interference light incident on the light receiving element is not the interference light from the other multi-optical axis photoelectric sensor 42, the plurality of light receiving elements of the multi-optical axis photoelectric sensor 41 are sequentially spaced at the same interval (between each light receiving element. It is extremely rare for interference light to enter at a light receiving interval. As described above, when the light projection timing of the multi-optical axis photoelectric sensor 41 is changed even though the interference light is incident at different intervals, the light projection timing of the multi-optical axis photoelectric sensor 41 is changed by this change. There is a possibility that the light projection timing of the multi-optical axis photoelectric sensor 42 becomes equal. In such a case, there is a possibility that a new erroneous detection occurs.

  The present invention has been completed based on the above situation, and an object thereof is to provide a multi-optical axis photoelectric sensor capable of preventing erroneous detection.

As means for achieving the above object, a multi-optical axis photoelectric sensor according to the invention of claim 1 includes a plurality of light projecting elements arranged in a line,
A plurality of light receiving elements arranged in a row facing each of the light projecting elements;
A light projection control means for repeating a light projection scanning operation for sequentially projecting the plurality of light projecting elements at a predetermined light projection timing at a predetermined period;
An enabling means for enabling a light receiving signal received by a light receiving element corresponding to the light projecting element among the light projected from each of the light projecting elements to be matched with a light projecting timing of the light projecting element;
Detection means for performing detection based on the level of the received light signal validated by the validation means;
Interference light detection means for detecting interference light based on a received light signal activated at the interference light detection timing, with a plurality of timings as interference light detection timings from the non-light projection period of the plurality of light projecting elements,
When the interference light is detected by the interference light detection means, the multi-optical axis photoelectric sensor comprising interference avoidance means for performing a predetermined interference avoidance operation,
In the interference light detection means, when interference light is detected from a plurality of light receiving elements during one light projection scanning operation, the interference light detected by the interference light detection means is projected from another multi-optical axis photoelectric sensor. comprising an interferometric light determining means for determining that the optical light,
The interference avoidance means includes
When the interference light determination unit determines that the interference light is light projected from another multi-optical axis photoelectric sensor, the interference light is performed while the interference light is transmitted to another multi-light. It is characterized in that the predetermined interference avoidance operation is not performed when it is determined that the light is not projected from the axial photoelectric sensor.

  According to a second aspect of the present invention, in the first aspect of the present invention, the interference light detection unit projects the light of the light projecting element that projects first among the plurality of light projecting elements for each light projecting scan operation. Interference light detection is performed for all periods from the time before a predetermined time to the time after the predetermined time of the light projecting timing of the last light projecting element, except for the time of projecting the light projecting elements. It is characterized by being set as timing.

According to a third aspect of the present invention, in the first or second aspect of the present invention, the predetermined interference avoidance operation of the interference avoidance unit is configured to vary a start timing of the light projection scan operation. Have

<Invention of Claim 1>
According to this configuration, when it is determined that the interference light is light projected from another multi-optical axis photoelectric sensor, the interference avoidance unit performs a predetermined interference avoidance operation, while the interference light is transmitted from the other multi-optical axis photoelectric sensor. When it is determined that the light is not projected from the optical axis photoelectric sensor, a predetermined interference avoidance operation is not performed. Therefore, when receiving light from a light source other than the other multi-optical axis photoelectric sensor (for example, a single optical axis photoelectric sensor or lamp), the interference avoiding operation is not performed. It is possible to prevent erroneous detection that occurs when the light projected from the sensor is received by the light receiving element at the light projection timing.

<Invention of Claim 2>
According to this configuration, it is possible to accurately determine whether or not the light is interference light from another multi-optical axis photoelectric sensor.

<Invention of Claim 3 >
According to this configuration, it is possible to avoid interference with other multi-optical axis photoelectric sensors without changing the entire period of the subsequent light projection scanning operation.

<Embodiment 1>
Embodiment 1 of the present invention will be described with reference to FIGS.
As shown in FIG. 1, the multi-optical axis photoelectric sensor 10 of the present embodiment is configured with the projector 20 and the light receiver 30 facing each other, and has, for example, four-channel optical axes L1 to L4. On the surface of the light projector 20 facing the light receiver 30, one (total of four) light projecting elements 21 a to 21 d (for example, LEDs) are arranged in a line in the vertical direction for each channel. Among them, light receiving elements 31a to 31d (for example, photodiodes) that are paired with the light projecting elements 21a to 21d are similarly arranged in the vertical direction on the surface facing the projector 20. Note that another multi-optical axis photoelectric sensor A is disposed in the vicinity of the multi-optical axis photoelectric sensor 10.

FIG. 2 shows an electrical configuration of the multi-optical axis photoelectric sensor 10 of the present embodiment.
The projector 20 is provided with drive circuits 22a to 22d for lighting the light projecting elements 21a to 21d, and the drive circuits 22a to 22d are driven by the light projecting elements 21a to 21d when receiving signals from the AND circuits 23a to 23d. Supply current. Output signals from the shift register 24 and the light-projecting CPU 25 are input to the AND circuits 23a to 23d. When signals from both are input, signals are sent to the drive circuits 22a to 22d. The light projection side CPU 25 receives a light projection timing signal St from a light reception side CPU 35 provided in the light receiver 30 described later, and outputs this light projection timing signal St to the shift register 24 and the AND circuits 23a to 23d.

  The light projection timing signal St is a pulse signal having a predetermined period (see FIG. 3), and is generated by the light receiving side CPU 35 in order to determine the lighting timing of the light projecting elements 21a to 21d. Within the scanning period (time T1) of the light projection timing signal St, four pulses are generated at equal intervals with a time ta, and a pause period tb is provided after the fourth pulse. Thereby, the light projection scanning operation in which the four light projecting elements 21a to 21d are sequentially turned on from the top to the bottom is repeatedly performed every period T1. Therefore, the AND circuits 23a to 23d, the shift register 24, the light emitting side CPU 25, and the light receiving side CPU 35 constitute a light projecting control means for sequentially lighting the light projecting elements 21a to 21d at a predetermined timing.

  On the other hand, the light receiver 30 includes light receiving amplifiers 32a to 32d that amplify light reception signals from the light receiving elements 31a to 31d at a predetermined amplification rate, respectively. The light receiving signals output from the light receiving amplifiers 32a to 32d are collected into a common signal line and taken into the comparator 34 via the analog switches 33a to 33d. An incident light blocking detection signal Sd (interference light detection signal Sy) that is high level if this received light signal is equal to or higher than the reference value set in the comparator 34 and low level if it is equal to or lower than the reference value is output to the light receiving side CPU 35. If the incoming light blocking detection signal Sd (interference light detection signal Sy) input to the light receiving side CPU 35 is at a high level, light (light received by the light projecting / receiving operation or interference light) is transmitted to the light receiving element 31a (to 31d). While it is detected that the light is incident, if the signal input to the light receiving side CPU 35 is at a low level, it is detected that light is not incident (shielded) on the light receiving elements 31a to 31d. Therefore, the light receiving side CPU 35 constitutes the detection means and the interference light detection means of the present invention.

  The light-receiving side CPU 35 is connected to each of the analog switches 33a to 33d, and each analog switch has a pulse whose cycle and phase match (synchronized) with the pulse of the light projection timing signal St described above every predetermined time (interval ta). A light reception timing signal Sr sequentially transmitted to 33a to 33d is transmitted.

Further, the light receiving side CPU 35, for each of the light projecting elements 21 a to 21 d, except for the time of projecting each of the light projecting elements 21 a to 21 d, is a predetermined time before and after each light projecting (for example, ta / 2 hours both before and after) The interference light detection timing signal Si to which the pulse is transmitted is sequentially transmitted to the analog switches 33a to 33d.
Thereby, the light receiving side CPU 35 projects light lastly from a time point before a predetermined time (for example, ta / 2) of the light projecting timing of the light projecting element 21a that projects light first among the light projecting elements 21a to 21d. Pulses are sent out in all periods except when light is projected by the light projecting elements 21a to 21d, up to a point after a predetermined time (for example, ta / 2) after the light projecting timing of the element 21d.

  When the analog switches 33 a to 33 d are turned on by the transmitted interference light detection timing signal Si, light reception signals from the light receiving elements 31 a to 31 d are input to the comparator 34.

  Thereby, when the light receiving side CPU 35 sends a pulse of the light receiving timing signal Sr (and the light projecting timing signal St), the light projecting elements 21a to 21d are in the lighting state, so that the light incident / light blocking detection signal output from the comparator 34 is obtained. With Sd, the light receiving side CPU 35 performs light shielding detection, and when the light receiving side CPU 35 sends out a pulse of the interference light detection timing signal Si, the light projecting elements 21a to 21d are in the non-lighting state, and thus output from the comparator 34. The light receiving side CPU 35 detects the interference light by the interference light detection signal Sy.

Next, processing of the light receiving side CPU 35 will be described with reference to FIGS.
When the power source of the multi-optical axis photoelectric sensor 10 is turned on, as shown in FIG. 2, the light receiving side CPU 35 transmits the light projection timing signal St to the light projection side CPU 25 to repeatedly perform the light projection scan operation at the cycle T1. . The light receiving side CPU 35 validates the light receiving signal by transmitting the light receiving timing signal Sr and the interference light detection timing signal Si to the analog switches 33a to 33d, and performs the light shielding detection and the interference detection.

<Shading detection>
As shown in FIG. 3, the light receiving side CPU 35 outputs a light projection timing signal St for sending a pulse at a predetermined timing and a light reception timing signal Sr for sending a pulse in synchronization with the light projection timing signal St. Then, the light projection scan operation (cycle T1) is started. Then, first, the light projecting element 21a (P1) is projected, and the light reception signal of the light received by the light receiving element 31a is validated, and the comparator 34 sets it as a high-level or low-level incident light-shielding detection signal Sd. The incident / light shielding detection signal Sd is input to the light receiving side CPU 35.

  As shown in FIG. 4, when the light-receiving / shielding detection signal Sd is received at the high level (light is incident) ("N" in S11), the light-receiving side CPU 35 receives the light-shielding detection signal Sd. The count N1 of the number of times of light shielding is initialized (S15), and the light shielding detection of the optical axis L2 is performed.

  On the other hand, when the incoming light blocking detection signal Sd is at the low level (light blocking), it is determined whether or not the optical axis L1 is in the light blocking state (light blocking count N1 = 1) during the previous light projection scan operation (S12), and the optical axis L1. Is in a light blocking state during the previous light projection scan operation (“Y” in S12), a light blocking determination is output to the output circuit 36 (S14), and then the light blocking detection of the optical axis L2 is performed.

  When the optical axis L1 is not in the light-shielding state during the previous light projection scan operation (N1 = 0, “N” in S12), the light-blocking count N1 of the optical axis L1 is set to 1 (S13), Shading detection of the axis L2 is performed.

  Next, when a second pulse of the light projection timing signal St and the light reception timing signal Sr is transmitted after a predetermined time (interval ta) from the transmission of the pulse, the light projecting element 21b (P2) is projected, The light receiving signal of the light received by the light receiving element 31b is validated, and the comparator 34 sets the incident / shielded light detection signal Sd at the high level or the low level, and this incident / shielded light detection signal Sd is input to the light receiving side CPU 35.

  The light receiving side CPU 35 receives the incoming / outgoing shading detection signal Sd, and if the incoming / outgoing shading detection signal Sd is at a high level (light is incident) (“N” in S16), it counts the number of shadings N2 of the optical axis L2. Initialization is performed (S20), and the light shielding detection of the optical axis L3 is performed.

  On the other hand, when the incoming light blocking detection signal Sd is at the low level (light blocking), it is determined whether or not the optical axis L2 is in the light blocking state (light blocking count N2 = 1) during the previous light projection scan operation (S17), and the optical axis L2 is determined. Is in the light blocking state during the previous light projection scanning operation (“Y” in S17), the light blocking determination is output to the output circuit 36 (S19), and then the light blocking detection of the optical axis L3 is performed.

  When the optical axis L2 is not in the light-shielding state during the previous light projection scan operation (N2 = 0, “N” in S17), the light-block count N2 of the optical axis L2 is set to 1 (S18), Shading detection of the axis L3 is performed.

  Then, the light receiving side CPU 35 performs the same processing as described above for the optical axes L3 (S21 to S25) and the optical axes L4 (S26 to S30), so that each of the optical axes L1 to L4 is blocked by the entry of an object. Detect if.

<Interference light detection>
As shown in FIGS. 3 and 5, the light-receiving side CPU 35 uses a pulse of the interference light detection timing signal Si for a predetermined time before the light-emission scanning operation start timing (light-emission / reception timing P 1 of the optical axis L 1) It is output to the analog switch 33a at ta / 2 hours before P1 (half the light projection interval ta). Then, when the interference light is incident on the light receiving element 31a by turning on the analog switch 33a, the received light signal is validated and input to the comparator 34, and the high level output from the comparator 34 is output. Alternatively, the low-level interference light detection signal Sy causes the light-receiving side CPU 35 to detect the interference light incident when the input interference light detection signal Sy is at a high level (S41).

  Next, the light-receiving side CPU 35 stops the pulse transmission of the interference light detection timing signal Si at the start timing of the projection scan operation (projection timing P1 of the projection element 21a), turns off the analog switch 33a, Pulses of the light projection timing signal St and the light reception timing signal Sr are output, and the above-described processing at the time of detecting the light shielding is performed (S42).

  When a predetermined light projecting time has elapsed, output of the light projecting timing signal St and the light receiving timing signal Sr is stopped, and it is determined whether the light projecting / receiving operation has been completed for all the four optical axes L1 to L4. (S43) Since only the optical axis L1 has completed the light projecting / receiving operation (“N” in S43), the interference light detection timing signal Si is sent again to the analog switch 33a to detect the interference light of the light receiving element 31a. Until ta / 2 hours elapses, and after ta / 2 hours elapses, the interference light detection timing signal Si is sent to the analog switch 33b until the interference light detection of the light receiving element 31b elapses ta / 2 hours elapses. Perform (S41).

  Next, at the light projection timing P2 of the light projecting element 21b, the light receiving side CPU 35 turns off the analog switch 33b and outputs pulses of the light projection timing signal St and the light reception timing signal Sr. Processing is performed (S42).

  Next, when a predetermined light projecting time has elapsed, output of the light projecting timing signal St and the light receiving timing signal Sr is stopped, and it is determined whether the light projecting / receiving operation has been completed for all four optical axes (S43). ) Since the light projecting / receiving operation is completed only up to the optical axis L2 (“N” in S43), the interference light detection timing signal Si is sent to the analog switch 33b again, and the above processing is performed for the four optical axes. It repeats until it complete | finishes about all (S41-S43).

  Then, by performing light shielding detection on the optical axis L4, after completing all four optical axes (“Y” in S43), the interference light detection timing signal Si is sent again to the analog switch 33d, and the light receiving element 31d. The interference light is detected until ta / 2 hours have elapsed (S44).

Next, the light receiving side CPU 35 counts the number of interference lights detected by the above processing (corresponding to “the number of interference lights detected within a predetermined time” of claim 3), and this number is specified in advance. It is determined whether or not the number of times (for example, twice) or more (S45, corresponding to “interference light determination means” of the present invention).
When the number of times is equal to or more than a predetermined number (2 times), the pause period tb until the next light emission scan operation is performed is reduced by t 'time and changed to the pause period tb-t' (scan cycle) T1 is changed to T2) (S46, corresponding to “interference avoiding means” of the present invention). On the other hand, when the number of interference lights is equal to or less than a predetermined number (for example, once), the time until the next light projection scan operation is not changed (the normal pause period tb (scan cycle) T1), S47, corresponding to “interference avoiding means” of the present invention).

  When the pause period tb is changed, the next light projection scan operation is performed after the pause period tb-t ′ has elapsed, and the interference light is detected a predetermined number of times or more by the (next) light projection scan operation. If not, the normal suspension period tb is entered again.

  According to the above configuration, when the interference light is interference light from another multi-optical axis photoelectric sensor A, the interference light is detected at a predetermined interval (period) as shown in FIG. In other words, the number of the interference light is also a predetermined (specified) number or more (for example, 4 times), so that the interference light at the time of detecting the light shielding can be changed by changing the start timing (pause period tb) of the subsequent projection scan operation. Can be avoided.

  On the other hand, when the interference light is not interference light from another multi-optical axis photoelectric sensor A (for example, a single optical axis photoelectric sensor, a lamp, etc.), as shown in FIG. The light is incident on the light receiving elements 31a to 31d at regular timing. For this reason, it is extremely rare that the light is periodically incident, and interference light is rarely detected a plurality of times in one light projection scanning operation. Therefore, when no interference light is detected a predetermined number of times (for example, twice) during one light projection scan operation, the pause period tb is changed by not changing the pause period tb of the next light projection scan operation. Thus, the light projection timing of the multi-optical axis photoelectric sensor 10 becomes equal to the light projection timing of light projected from the other multi-optical axis photoelectric sensor A (timing of interference light from the multi-optical axis photoelectric sensor A). It is possible to prevent erroneous detection caused by the error.

  Further, the light receiving side CPU 35 lasts from a time point before a predetermined time (ta / 2) of the light projecting timing of the light projecting element 21a that projects the first light among the light projecting elements 21a to 21d for each light projecting scan operation. In the period up to a time point after a predetermined time (ta / 2) of the light projecting timing of the light projecting element 21d that projects light, all the periods except the time of projecting the light projecting elements 21a to 21d are set as the interference light detection timing. ing. Therefore, for example, by detecting the interference light in a wider period compared to a configuration in which the interference light is detected just before or just after the projection, the interference light is more accurately detected by other multi-optical axis photoelectrics. It can be determined whether or not the sensor A is used. In addition, the interference light is not detected as the rest period tb from the predetermined time (ta / 2) of the light projection timing of the light projecting element 21d that projects the last light until the start of the next light projection scan operation. The processing on the light receiving side CPU 35 can be reduced.

  Furthermore, since it is determined that the interference light is light projected from another multi-optical axis photoelectric sensor A when the number of detected interference light is a predetermined number of times (twice) or more, It is possible to more stably determine whether or not the light is interference light from another multi-optical axis photoelectric sensor A.

  In addition, since the predetermined interference avoidance operation is to change the start timing (pause period tb) of the light projection scan operation, without changing the cycle T1 of the light projection scan operation for all the subsequent light projection scan operations, Interference with other multi-optical axis photoelectric sensors A can be avoided.

<Embodiment 2>
Next, Embodiment 2 of the present invention will be described. Hereinafter, about the same structure, the same code | symbol is attached | subjected and description is abbreviate | omitted and only a different part is demonstrated.
In the first embodiment, the light-receiving side CPU 35 determines that the interference light from the other multi-optical axis photoelectric sensor A is detected when it detects that the interference light has entered a predetermined number of times.

On the other hand, in the second embodiment, when a plurality of interference lights are detected, the interval (cycle) of the interference lights detected twice consecutively is a predetermined time (for example, a pre-stored multi-optical axis photoelectric sensor). If it is the light projection interval ta (cycle)), it is detected that the light is interference light from another multi-optical axis photoelectric sensor A.
For example, since interference light from other light sources (single optical axis photoelectric sensor, lamp, etc.) has a non-constant period, the interference light is separated from other multi-optical axis photoelectric sensors A by comparing with a predetermined time (period). Can be easily determined.

<Other embodiments>
The present invention is not limited to the embodiments described with reference to the above description and drawings. For example, the following embodiments are also included in the technical scope of the present invention, and further, within the scope not departing from the gist of the invention other than the following. Various modifications can be made.

  (1) In the above embodiment, the pause period tb is changed on the condition that the interference light is detected twice. However, the present invention is not limited to this. For example, on the condition that the interference light is detected three times or more. The suspension period tb may be changed.

  (2) In the above-described embodiment, the pause period tb is changed short. However, the pause period tb is not limited to be changed short, but can be changed longer, and the interval ta between the pulses of the projection timing signal is also possible. May be changed.

  (3) In the above embodiment, the predetermined time (the “predetermined time” in claim 3) for counting the number of times interference light is incident is a time point before the predetermined time ta / 2 of the first light projection timing in one light projection scan operation. From the time until the time after the predetermined time ta / 2 of the last light projection timing, the period excluding the time of light projection is used, but it is not limited thereto. For example, the number of interference lights for a plurality of optical axes (light receiving elements) may be counted at a plurality of timings during one projection scan operation, and the number of interference lights over a plurality of projection scan operations. May be counted.

Configuration perspective view of multi-optical axis photoelectric sensor Circuit diagram showing electrical configuration of multi-optical axis photoelectric sensor (A) Time chart showing operation of multi-optical axis photoelectric sensor and timing of interference light from other multi-optical axis photoelectric sensor (b) Showing operation of multi-optical axis photoelectric sensor and timing of interference light from other light source Time chart Flow chart showing processing at the time of shading detection Flow chart showing processing of interference light detection Configuration perspective view of a conventional multi-optical axis photoelectric sensor

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Multi-optical axis photoelectric sensor 21a-21d ... Light projection element 22a-22d ... Drive circuit 24 ... Shift register 31a-31d ... Light receiving element 33a-33d ... Analog switch 34 ... Comparator A ... Other multi-optical axis photoelectric sensor CPU25 ... Emitting side CPU 35 ... Receiving side L1 to L4 ... Optical axis St ... Emitting timing signal Sr ... Receiving timing signal Si ... Interference light detection timing signal Sd ... Incident light shielding detection signal Sy ... Interference light detection signal T1 ... Scan cycle tb ... Pause period

Claims (3)

A plurality of light emitting elements arranged in a line;
A plurality of light receiving elements arranged in a row facing each of the light projecting elements;
A light projection control means for repeating a light projection scanning operation for sequentially projecting the plurality of light projecting elements at a predetermined light projection timing at a predetermined period;
An enabling means for enabling a light receiving signal received by a light receiving element corresponding to the light projecting element among the light projected from each of the light projecting elements to be matched with a light projecting timing of the light projecting element;
Detection means for performing detection based on the level of the received light signal validated by the validation means;
Interference light detection means for detecting interference light based on a received light signal activated at the interference light detection timing, with a plurality of timings as interference light detection timings from the non-light projection period of the plurality of light projecting elements,
When the interference light is detected by the interference light detection means, the multi-optical axis photoelectric sensor comprising interference avoidance means for performing a predetermined interference avoidance operation,
In the interference light detection means, when interference light is detected from a plurality of light receiving elements during one light projection scanning operation, the interference light detected by the interference light detection means is projected from another multi-optical axis photoelectric sensor. comprising an interferometric light determining means for determining that the optical light,
The interference avoidance means includes
When the interference light determination unit determines that the interference light is light projected from another multi-optical axis photoelectric sensor, the interference light is performed while the interference light is transmitted to another multi-light. The multi-optical axis photoelectric sensor, wherein the predetermined interference avoidance operation is not performed when it is determined that the light is not projected from the axial photoelectric sensor. The interference light detection means includes
For each projection scanning operation, the predetermined projection timing of the last projecting element from the time before the projection timing of the first projecting element to project among the plurality of projecting elements is predetermined. 2. The multi-optical axis photoelectric sensor according to claim 1, wherein all periods other than the time of light projection of the plurality of light projecting elements are set as interference light detection timings up to a time point after the time. 3. The multi-optical axis photoelectric sensor according to claim 1, wherein the predetermined interference avoiding operation of the interference avoiding unit is to change a start timing of the light projection scanning operation.

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