JP3763202B2 - Photoelectric sensor and multi-optical axis photoelectric sensor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a photoelectric sensor, and more particularly to a photoelectric sensor that can prevent malfunction due to mutual interference.
[0002]
[Prior art]
A multi-optical axis photoelectric sensor is conventionally used as a safety device for a press machine or an approach warning device in a hazardous area. The multi-optical axis photoelectric sensor is arranged such that a projector having a plurality of light projecting elements and a light receiver having a plurality of light receiving elements corresponding to each of the plurality of light projecting elements are opposed to each other. By forming an optical axis between each of the plurality of light projecting elements and the plurality of light receiving elements, a large number of optical axes (optical paths) are formed between the light projector and the light receiver. Then, a detection area is set between the light projector and the light receiver, and a plurality of light projecting elements are caused to emit light sequentially, and a light receiving operation is performed in synchronization with the light projecting timing by the light receiving elements corresponding to the respective light projecting elements. It is. In the multi-optical axis photoelectric sensor, when there is a light-shielding object in the detection area, the light-receiving element eliminates the light-receiving signal, so that the object detection signal can be output by judging the light-shielding state of the optical axis based on the light-receiving element. In a place where the multi-optical axis photoelectric sensor is used, the press device is stopped based on such an object detection signal, or an alarm is issued by detecting the entry of a person into the hazardous area into the factory. To prevent accidents.
[0003]
By the way, when a plurality of photoelectric sensors are provided close to each other, mutual interference may occur. Such photoelectric sensor mutual interference detection is disclosed in, for example, Japanese Patent Laid-Open No. 5-75421. According to the publication, the light receiving function is validated at the time of non-projection during normal operation, which is called a disturbance light detection state. If the frequency of light reception in the disturbance light detection state is low, a warning is given. If the frequency of light reception in the disturbance light detection state is high, the output is made the same as in the light shielding state, and that state is maintained until the power is reset.
[0004]
[Problems to be solved by the invention]
Conventional photoelectric sensors detect ambient light as described above. However, in this case, when the disturbance light is a mutual interference light from a photoelectric sensor of the same type as that of itself, it takes time to find the interference because the light projection period of the interference side and the interference side are very close. Therefore, the photoelectric sensor will stop functioning unexpectedly, and even if the machine controlled by the photoelectric sensor stops or tries to prevent mutual interference by changing the installation, until it is confirmed that the new installation is correct Therefore, the convenience may be reduced.
[0005]
This state will be described with reference to the drawings. FIG. 9 is a diagram showing the light reception timing (a) of the photoelectric sensor for detecting the mutual interference light and the light projection timing (b) of disturbance light. Referring to FIG. 9, for example, in a multi-optical axis photoelectric sensor, the light projection period (= light reception period) of a sensor that receives disturbance light is 5 ms, and the light projection period of a sensor that provides disturbance light is 5.001 ms (relative error 0. 0). 02%). As shown in FIG. 9, since the light reception timing (a) of the sensor and the light projection timing (b) of disturbance light are shifted by 0.001 ms, both timings approach each other by 0.001 ms. Therefore, mutual interference can be detected only when t = 22.5 s. If the initial deviation between the disturbance light timing and the disturbance light detection timing is 4.5 ms, the time required until the disturbance light detection is 5.001 ms × 4.5 ms / 0.001 ms = 22.5 s. When an algorithm that stops sensor output when ambient light is detected is employed, there may be a state in which the photoelectric sensor is stopped before long. As a result, there is a problem in convenience for the user.
[0006]
Further, assuming that the light projection pulse width is 5 μs and the light receiving axis effective period is 10 μs, the duration of mutual interference is 5 ms × (5 μs + 10 μs) /0.001 ms = 75 ms. During this period, even if the optical axis is interrupted, the sensor does not react and is in a malfunctioning state.
[0007]
The present invention has been made to solve the above-described problems, and an object thereof is to provide a photoelectric sensor capable of reliably detecting the presence or absence of mutual interference in a short time.
[0008]
[Means for Solving the Problems]
  In the photoelectric sensor according to the first aspect, the light projecting unit and the light receiving unit operate in synchronization with each other at a predetermined cycle. The photoelectric sensor has means for stopping the light projection of the light projecting unit and, ThrowLight receiving unit when light projection is stoppedMutual interference by detecting the presence or absence of light reception at a predetermined cyclelightDetermine the presence or absence ofDoDiscriminationMeans,Light reception timing means for instructing detection timing of presence / absence of light reception by the determination means, and determinationmeansDue to mutual interferencelightIt is determined that there isDisplay means for displaying that effect.Thus, the light receiving timing means performs a one-round process for sequentially shifting the detection timing by the discriminating means over the entire phase of a predetermined period until it is discriminated that the mutual interference light is incident by the discriminating means..
[0009]
  The light receiving unit shifts the phase of a predetermined cycle while the light emitting unit does not project light.Mutual interferenceReceive lightMutual interferenceThe presence or absence of lightDiscriminationAndMutual interferenceWhen there is light, a message to that effect is displayed. as a result,ConstantWith light of periodPhaseThe presence or absence of mutual interference can be reliably detected in a short time.
[0010]
  The multi-optical axis photoelectric sensor according to claim 2 is:Each has a pair of optical axes, each constantOperates synchronously with the periodTransmitter and receiverMultipleThe light projecting unit and the light receiving unit corresponding to each optical axis operate in synchronization with each other at a predetermined cycle.. The multi-optical axis photoelectric sensor has means for stopping the light projection of a plurality of light projecting units., DoubleIn the light emission stop state of several light emitting parts, DoubleNumber of light receiving partsMutual interference by simultaneously detecting the presence or absence of light reception at a predetermined cyclelightDetermine the presence or absence ofDoDiscriminationMeans,Light reception timing means for instructing detection timing of presence / absence of light reception by the determination means, and determinationmeansDue to mutual interferencelightIt is determined that there isDisplay means for displaying that effect.Thus, the light receiving timing means performs a one-round process for sequentially shifting the detection timing by the discriminating means over the entire phase of a predetermined period until it is discriminated that the mutual interference light is incident by the discriminating means..
[0011]
  In a multi-optical axis photoelectric sensor having a plurality of light projecting units and a light receiving unit, the plurality of light receiving units shift the phase of a predetermined cycle without the light projecting unit projecting light.Mutual interferenceDetect the presence of light,Mutual interferenceWhen light is detected, a message to that effect is displayed. Therefore, in the multi-optical axis photoelectric sensor,ConstantInterfering light that is projected periodically can be reliably detected in a short time.
[0012]
  The multi-optical axis photoelectric sensor according to claim 3 includes a plurality of light projecting units and light receiving units, each of which forms a pair of optical axes and operates synchronously.The light projecting unit and the light receiving unit corresponding to each optical axis operate in synchronization with each other at a predetermined cycle.. Multi-optical axis photoelectric sensorpluralMeans for stopping the light projection of the light projecting unit;An optical axis selection means for repeatedly selecting each of the plurality of optical axes at a predetermined light reception period at the time of external diagnosis in a light projection stop state of the plurality of light projecting units;lightPartIn the light emission stop state ofSelect by optical axis selection meansSelected receiverMutual interference by detecting the presence or absence of light reception atlightDetermine the presence or absence ofDoDiscriminationMeans,Light reception timing means for instructing the detection timing of the presence or absence of light reception by the discrimination means, and mutual interference by the discrimination meanslightIt is determined that there isWhen it isTheDisplay means to displayThus, the light receiving timing means performs a round process in which the detection timing by the determining means is sequentially shifted over the entire phase of the light receiving period at the time of external diagnosis until it is determined by the determining means that mutual interference light is incident.
[0013]
  In a multi-optical axis photoelectric sensor having a plurality of light projecting units and light receiving units, ThrowThe light receiving unit selected when the light unit is not projectingDuring external diagnosisWhile shifting the cycleMutual interferenceReceives light. AndMutual interferenceWhen light is received, a message to that effect is displayed. As a result, it is possible to detect the presence or absence of interference of a desired optical axis among the plurality of optical axes.
[0014]
  In the multi-optical axis photoelectric sensor according to claim 4, the display means of the multi-optical axis photoelectric sensor in claim 3 is selected.Mutual interferenceDisplay that can identify the optical axis in which light is detected.
[0015]
  Mutual interferenceSince the display that can identify the optical axis in which the light is detected is performed, it is possible to detect which optical axis among the plurality of optical axes is causing interference.
[0016]
  In the photoelectric sensor according to claim 5, claims 1 to 3 are provided.Any one ofIs connected to a predetermined device,DiscriminationMeansMutual interferenceWhen light is detected, a predetermined signal is output to the apparatus.
[0017]
  Claims 1 to 3Any one of1 photoelectric sensorMutual interferenceAfter detecting the light,Mutual interferenceAs long as there is no light, the device keeps the output in the same state as the light shield. As a result, safety is reliably ensured in an apparatus using a photoelectric sensor.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
(I) First embodiment
Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a functional block diagram showing the main part of a single optical axis reflective photoelectric sensor. Referring to FIG. 1, a reflective photoelectric sensor 10 includes a microcomputer 11 that achieves most of the functions of the photoelectric sensor, a light projecting circuit 12 that is connected to the microcomputer 11 and controls an LED 15 that performs light projection, and a light receiving unit. A light receiving circuit 13 for inputting a signal received by a photodiode (hereinafter abbreviated as PD) 16, an output circuit 14 for outputting a control output signal to a device (not shown), and when disturbance light is detected by the PD 16 Includes a disturbance light receiving indicator lamp 19 for displaying the fact and an indicator lamp 18 for displaying ON / OFF. The microcomputer 11 is further connected with an EEPROM 23 for storing data. The photoelectric sensor 10 further includes a power supply circuit 17, and power is supplied to the power supply circuit 17 via the power supply terminal 20.
[0019]
The microcomputer 11 includes a light projection timing unit 25 that instructs the light projection timing, a light reception timing unit 26 that instructs the light reception timing, and a light projection stop unit that stops the light projection at the time of diagnosis according to the signal from the external diagnosis input terminal 21. 24, a gate unit 27 that receives light at a predetermined timing by the light receiving circuit 13 according to the light receiving timing unit 26, and a determination unit 28 that determines whether light is received by the light receiving circuit 13.
[0020]
Normally, light from the LED that is the light projecting unit 15 is reflected by the detection object 40, and the detection light is input to the photodiode that is the detection unit 16, and the presence or absence of the detection object 40 is determined by the determination unit 28.
[0021]
Light projection and light reception are synchronously controlled by a synchronization signal from the light projection timing unit 25 to the light reception timing unit 26. This photoelectric sensor 10 has an external diagnostic input terminal 21. When an external diagnostic function is selected from a device (not shown), the light projection is stopped and the output is kept in a safe state (OFF). At this time, the light reception timing unit 25 shifts the light reception timing (phase) little by little as described later. A signal received by the PD, which is the light receiving unit 16, is amplified and filtered by the light receiving circuit 13 and then sent to the gate unit 27. The gate unit 27 passes the light reception signal to the determination unit 28 for the period controlled by the light reception timing unit 26.
[0022]
FIG. 6 shows the overall appearance of a single optical axis reflective photoelectric sensor 81 to which the present invention is applied. FIG. 2 is a timing chart showing the relationship between light reception timing and disturbance light timing during external diagnosis. As temporal conditions, the light projection period (= light reception period) of the sensor is 100 μs, the light projection pulse width is 10 μs, and the light reception effective period is 10 μs.
[0023]
Referring to FIG. 2, (a) shows the light reception timing of the sensor when the external diagnostic function is selected, and (b) shows the timing of disturbance light.
[0024]
Next, a procedure for detecting disturbance light (mutual interference light) will be described.
(1) The presence / absence of incident light is determined for two cycles at the normal light projection timing.
[0025]
(2) If there is a light incident state even once, the light incident is monitored for another five cycles.
(3) According to the majority logic, for example, when a light incident state is detected in 4 cycles or more in 7 cycles, it is determined that there is disturbance light. Thereafter, ambient light detection is continued with the same phase. If it is determined that there is no disturbing light on the way, detection of presence / absence of incident light is started again from (1).
[0026]
(4) Above, when there is no incident light state in (2) and when the incident light state is three times or less in (3), it is delayed by 5 μs with respect to the original synchronizing signal of the incident light, and (1) (2) (3) is executed (phase shift is performed).
[0027]
(5) If it is determined that there is no disturbing light, the light reception timing is further delayed by 5 μs to delay the total by 10 μs, and (1), (2), and (3) are executed.
[0028]
{Circle around (6)} When it is determined that there is no possibility of mutual interference, the light reception timing is further delayed by 5 μs for a total delay of 15 μs. Similarly, it is delayed by 20, 25,... 95 μs. If it is still determined that there is no possibility of mutual interference, the delay time is set to 0 and the process starts again from (1).
[0029]
(7) The above one-round processing time is a maximum of 0.1 ms × 7 cycles × 20 (delay processing) = 14 μs.
[0030]
A specific example will be described with reference to FIG. As described in (4) above, when there is no light incident state, the light reception timing (a) of the sensor when the external diagnostic function is selected is shifted by 5 μs, that is, the phase is shifted (a1). Then, light is received in the usual 100 μs (a2). Here, the point b1 coincides with the disturbance light timing (b). Since the light incident state is detected in four cycles or more at b2, the determination unit 28 determines that there is disturbance light. Then, the fact is displayed on the disturbance light receiving indicator lamp 19. As this display state, the disturbance light receiving indicator lamp 19 may be blinked. Further, the “light incident at the time of external diagnosis” information is recorded in the storage element of the EEPROM 23. This recording is not erased by turning the power on and off, and is maintained until “light shielding during external diagnosis” is recorded. In other words, even if the EEPROM 23 retains the “light input at the time of external diagnosis” information and the selection of the external diagnosis function is stopped or the power is turned ON / OFF, the output is in a safe state according to the “light input at the time of external diagnosis” information ( OFF). “Light shielding during external diagnosis” information is recorded when the light shielding state continues for 28 ms or longer. Here, 28 ms is twice the maximum one-round processing time of 14 ms, and the light-shielding information at the time of external diagnosis is recorded only when disturbance light is not received after two rounds.
[0031]
The photoelectric sensor 10 returns from the external diagnostic mode to the normal mode when the external diagnostic input signal is not received for a certain period after the “light shielding during external diagnosis” information is recorded.
[0032]
(Ii) Second embodiment
FIG. 3 is a block diagram showing the main part of the controller of the multi-optical axis photoelectric sensor. Referring to FIG. 3, multi-optical axis photoelectric sensor 51 includes a projector 52 and a light receiver 63. The projector 52 includes a microcomputer 55 that achieves the main functions of the projector, a sequential projector circuit 59 that is connected to the microcomputer 55 and outputs a projection signal to the plurality of projectors LED1 to LED8, and a search for disturbance light. A disturbance light search indicator lamp 54 for displaying that the display is being performed, and a power supply circuit 53 are included. The microcomputer 55 functions as a light projection timing unit 56 that controls the light projection timing, a light projection stop unit 57 that stops the light projection, and a transmission unit 58 that transmits the fact to the light receiver 63 during external diagnosis.
[0033]
The light receiver 63 includes a microcomputer 69 that achieves a main function as the light receiver 63, an optical axis selection circuit 75 that receives light reception signals from the plurality of light receiving portions PD1 to PD8, and can select a desired optical axis. The light receiving circuit 67 is connected to the optical axis selection circuit 75 and transmits to the microcomputer 69 that light is received from the selected optical axis, the ON / OFF indicator lamp 65, and the disturbance light other than the projector 52. A disturbance light receiving indicator lamp 66 for displaying that the light has been received, and an output circuit 68 for outputting the result of determination of the presence or absence of disturbance light by the microcomputer 69 to an external device (not shown) via the control output terminal 77; including. An EEPROM 74 is connected to the microcomputer 69, and predetermined data described later is recorded therein. The light receiver 63 includes a power supply circuit 64 to which power is supplied from the outside via a power supply terminal 76.
[0034]
The microcomputer 69 receives a synchronization / external diagnosis instruction signal from the projector 52, a light reception timing unit 72 for setting the light reception timing received from the projector 52 via the reception unit, and the timing according to the light reception timing. It functions as a gate unit 70 for passing a light receiving / non-receiving signal from the light receiving circuit 67 and a determining unit 71 for determining the presence / absence of ambient light.
[0035]
The transmitter 58 of the projector 52 and the receiver 73 of the light receiver 63 are connected by a cable that transmits a synchronization / external diagnosis instruction signal 78.
[0036]
The projector 52 has an external diagnostic input terminal 61. If the external input diagnosis function is not selected by an external device (not shown), a synchronization signal is transmitted to the light receiver 63. If the external input diagnosis function is selected, an external diagnosis instruction signal is sent to the light receiver 63. Send. The projector 52 normally projects the LEDs of each optical axis sequentially, but stops the projection of all the optical axes when the external diagnostic function is selected. The light receiver 63 normally selects the light receiving signals of the optical axes PD1 to PD8 corresponding to the LED1 to LED8 being projected, but when the external diagnostic function is selected, the light receiving signals of all the optical axes are simultaneously selected. Select and keep the output safe (OFF). At this time, the light reception timing function shifts the light reception timing (phase) little by little as described later. The signal received by the light receiving unit PD is amplified and filtered by the light receiving circuit 67 and then sent to the gate unit 70. The gate unit 70 passes the light reception signal to the determination unit 71 for the period controlled by the light reception timing unit 72.
[0037]
FIG. 7 shows an external view of a light projector 52 and a light receiver 63a constituting the multi-optical axis photoelectric sensor 51 according to the second embodiment. LED1 to LED8 of the projector 52 and PD1 to PD8 of the light receiver 63a constitute the optical axis 82, respectively.
[0038]
FIG. 4 is a timing chart showing the relationship between light reception timing and disturbance light timing at the time of external diagnosis in the multi-optical axis photoelectric sensor shown in FIG. (A) shows disturbance light, (b) shows a normal light receiving state, and (c) shows a light receiving state at the time of external diagnosis. Here, the disturbance light shown in (a) is projected from a multi-optical axis photoelectric sensor with eight optical axes shown in FIG. 3, and light from the first optical axis (the optical axes of LED1 and PD1) is detected. Shall be.
[0039]
(D) is an enlarged view of disturbance light (a). (E)-(i) is an enlarged view of the light reception state at the time of external diagnosis of (c), (e) shows the state of t = 0-15 ms, (f) shows the state of t = 15-30 ms. (G) shows a state of t = 30 to 45 ms, (h) shows a state of t = 255 to 270 ms, and (i) shows a state of t = 270 to 285 ms.
[0040]
Referring to FIG. 4, the light projection period (= light reception period) of the 8-optical axis photoelectric sensor that receives disturbance light as a time condition is 5 ms, and the light emission period of the 8-optical axis photoelectric sensor that provides disturbance light is 5.001 ms ( (Relative error 0.02%), each optical axis selection switching interval is 100 μs, the initial deviation between the disturbance light timing and disturbance light detection state timing is 85 μs, the light emission pulse width is 5 μs, and the light receiving axis effective period is 10 μs. And Further, as an optical condition, disturbance light is incident on all optical axes of the light receiver 63. The light receiving parts PD1 to PD8 detect disturbance light (mutual interference light) with the following algorithm.
[0041]
{Circle around (1)} All optical axes are simultaneously enabled every 100 μs for 5 ms × 3 periods to determine the presence or absence of incident light (FIG. 4E).
[0042]
(2) If a light incident state is detected in two or more cycles in three cycles, it is determined that ambient light is present. Thereafter, the ambient light detection function is continued with the same phase. If it is determined that there is no disturbing light in the middle, the presence / absence determination of light incident is started again from (1).
[0043]
(3) If the incident light state is less than once in (2) above, the light reception timing is delayed by 5 μs with respect to the original synchronization signal (FIG. 4 (f)), and (1) (2) is executed (phase) shift).
[0044]
{Circle around (4)} When it is determined that there is no disturbing light, the light receiving timing is further delayed by 5 μs to delay by a total of 10 μs, and the steps {circle around (1)} {circle around (2)} are executed (FIG. 4G).
[0045]
{Circle around (5)} When it is determined that there is no disturbing light, the light reception timing is further delayed by 5 μs for a total delay of 15 μs. Similarly, the delays are delayed by 20, 25,... 95 μs (FIGS. 4H and 4I). If it is still determined that there is no ambient light, the delay time is set to 0 and the process starts again from (1).
[0046]
(6) The above one-round processing time is 5 ms × 3 periods × 20 (delay type) = 300 ms
Under this condition, disturbance light can be detected at 5 ms × 3 periods × (85 μs / 5 μs + 1 + 1) = 285 ms.
[0047]
As a result of the external diagnosis, the light receiver 63 performs some display while detecting that the light is in the incident state. For example, the ON / OFF indicator lamp 65 is blinked. Further, the “light incident at the time of external diagnosis” information is stored in a storage element such as the EEPROM 74. This record is not erased by turning the power ON / OFF, and is maintained until “light shielding during external diagnosis” is stored. In other words, even if the light receiver 63 stops selecting the external diagnostic function or turns the power ON / OFF while holding “light incident at the time of external diagnosis”, the output is controlled according to the information “light incident at the time of external diagnosis”. The At this time, the output is not in danger. “Light shielding during external diagnosis” information is recorded when the light shielding state continues for 300 ms or longer.
[0048]
The light receiver 63 moves from the external diagnostic mode to the normal mode when the external diagnostic input signal is received from the projector 52 for a certain period after the “light shielding during external diagnosis” information is recorded. Wait for start signal.
[0049]
In FIG. 4, the disturbance light enlarged view of (d) should be taken into account of the fraction of 5.001 ms−5.0 ms = 1 μs as described above, but is omitted here. The light receiver 63 detects disturbance light at the time indicated by i1 in (i).
[0050]
(Iii) Third embodiment
Next, a third embodiment of the present invention will be described. Also in the third embodiment, the configuration of the multi-optical axis photoelectric sensor is the same as that of the second embodiment shown in FIG. FIG. 5 is a diagram showing the relationship between the light reception timing and disturbance light timing of the projector 52 and the light receiver 63 according to the third embodiment of the present invention. (A) shows disturbance light, (b) shows a normal light reception state, and (c) shows a light reception state at the time of external diagnosis. The disturbance light in (a) is projected from a multi-optical axis photoelectric sensor having eight optical axes, and light from the eighth optical axis (LED8-PD8) is detected.
[0051]
Referring to (c), it is assumed that disturbance light enters the first optical axis (LED1-PD1).
[0052]
(D) is an enlarged view of the disturbance light shown in (a), and (e) to (i) are enlarged views for each time of the light receiving state (c) at the time of external diagnosis. (E) shows a state of t = 0-15 ms, (f) shows a state of t = 15-30 ms, (g) shows a state of t = 30-45 ms, and (h) shows t = 2055. The state of 2070 ms is shown, and (i) shows the state of t = 2070-2085 ms. In (d), the disturbance light of the optical axis 1 and the optical axis 2 is optically not received as disturbance light, and is indicated by a dotted line. In addition, although a fraction of 5.001 ms−5.0 ms = 1 μs should be considered here, it is omitted here.
[0053]
This embodiment is different from the second embodiment in that the light receiver 63 sequentially selects the light reception signals of the respective optical axes when the external diagnostic function is selected. In this embodiment, the light projection period (= light reception period) of the 8-optical axis photoelectric sensor that receives disturbance light under temporal conditions is 5 ms, and the light emission period of the 8-optical axis photoelectric sensor that provides disturbance light is 5.001 ms (relative). The error is 0.02%), the selection switching interval of each optical axis is 100 μs, the initial deviation between the disturbance light timing and the disturbance light detection state timing is 685 μs, the light projection pulse width is 5 μs, and the light receiving axis effective period is 10 μs. As an optical condition, it is assumed that disturbance light enters the first optical axis of the light receiver 63 from the eighth optical axis. Although the initial deviation between the disturbance light timing and the disturbance light detection state timing is 685 μs here, it goes without saying that this value can be set arbitrarily.
[0054]
Next, an algorithm for detecting disturbance light (mutual interference light) of the light receiver 63 will be described.
[0055]
{Circle around (1)} Each optical axis is sequentially enabled, and for 5 ms × 3 cycles, the presence / absence of disturbance light is detected for three cycles for each optical axis. The start period of each cycle is 1.667 ms (FIG. 5 (c)).
[0056]
(2) If a light incident state is detected in two or more cycles in three cycles, it is determined that ambient light is present. Thereafter, the ambient light detection function is continued with the same phase. If it is determined that there is no disturbing light on the way, detection of presence / absence of incident light is started again from (1).
[0057]
(3) If the incident light state is less than once in (2) above, (1) (2) is executed with the light receiving timing delayed by 5 μs with respect to the original synchronization signal (FIG. 5 (f)).
[0058]
{Circle around (4)} When it is determined that there is no disturbing light, the light receiving timing is further delayed by 5 μs to delay by a total of 10 μs, and the steps {circle around (1)} {circle around (2)} are executed.
[0059]
{Circle around (5)} When it is determined that there is no disturbing light, the light reception timing is further delayed by 5 μs for a total delay of 15 μs. In the same manner, the delay time is delayed by 20, 25,..., 1660 μs.
[0060]
(6) The above one-round processing time is 5 ms × 3 periods × 333 (delay type) = 4995 ms
Under this condition, disturbance light can be detected at 5 ms × 3 periods × (685 μs / 5 ms + 1 + 1) = 2085 ms.
[0061]
  In the present embodiment, FIG.5As shown in (c), the external diagnosis is performed in the first to third cycles during 5 ms, which is one period of disturbance light, in the external diagnosis light reception, so that the external diagnosis can be performed in a short time.
[0062]
As a result of the external diagnosis, the light receiver 63 performs some display on each optical axis while detecting that ambient light is in the incident light state. FIG. 8 is a diagram showing a configuration example of a multi-optical axis photoelectric sensor in the case of performing such display. Referring to FIG. 8, the light receiver 63b is provided with a disturbance light receiving indicator lamp 66 for each optical axis adjacent to the light receiving portion of each optical axis, and only the disturbance light receiving indicator lamp of the optical axis that detects the disturbance light. Flashes. Thereby, the installer of the photoelectric sensor can easily know to which optical axis the disturbance light is incident.
[0063]
The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a main part of a reflective photoelectric sensor with a single optical axis.
FIG. 2 is a timing chart showing the relationship between light reception timing and disturbance light timing during external diagnosis in a single optical axis reflective photoelectric sensor.
FIG. 3 is a block diagram showing a main part of a transmissive multi-optical axis photoelectric sensor.
FIG. 4 is a timing chart showing the relationship between light reception timing and disturbance light timing at the time of external diagnosis in a transmissive multi-optical axis photoelectric sensor.
FIG. 5 is a timing chart showing the relationship between light reception timing and disturbance light timing based on the third embodiment of the present invention.
FIG. 6 is a diagram showing an appearance of a single optical axis photoelectric sensor.
FIG. 7 is a diagram showing an installation example of a multi-optical axis photoelectric sensor.
FIG. 8 is a diagram showing an installation example of a multi-optical axis photoelectric sensor according to another embodiment of the present invention.
FIG. 9 is a diagram for explaining a conventional problem.
[Explanation of symbols]
10 Photoelectric sensor
11 Microcomputer
12 Floodlight circuit
13 Light receiving circuit
14 Output circuit
15 Light Emitting Unit (LED)
16 Light receiver PD (photodiode)
21 External diagnostic input terminal
23 EEPROM
31 Projection timing section
32 Light reception timing section
33 Projection stop
34 Gate part
35 Discrimination part
40 sensing object
51 Transmission type multi-optical axis photoelectric sensor
52 Floodlight
55 Microcomputer
56 Projection timing section
57 Light emission stop
58 Transmitter
61 External diagnostic input terminal
63 Receiver
66 Disturbance light indicator lamp
67 Light receiving circuit
68 Output circuit
69 Microcomputer
70 Gate part
71 Judgment part
72 Light reception timing section
73 Receiver
74 EEPROM
75 Optical axis selection circuit

Claims (5)

A photoelectric sensor in which the light projecting unit and the light receiving unit operate synchronously at a predetermined cycle,
Means for stopping the light projection of the light projecting unit ;
In emission stop state before Kito light unit, by detecting the presence or absence of light reception in the light receiving unit at the predetermined cycle, and determination means for determining the presence or absence of the interference light,
A light reception timing means for instructing a detection timing of the presence or absence of light reception by the determination means;
If it is determined that there is a light input of the interference light by the determination means, seen including a display means for displaying to that effect,
The light reception timing means performs a round process of sequentially shifting the detection timing by the determination means over the entire phase of the predetermined period until the determination means determines that there is incident light of the mutual interference light . Photoelectric sensor. Each forms the optical axis of the pair, and a light receiving portion and the light projecting unit which operates synchronously with multiple perforated, and the light receiving portion and the light projecting portion corresponding to the optical axis sequentially synchronized with a predetermined period A multi-optical axis photoelectric sensor that operates ,
Means for stopping the light projection of the plurality of light projecting units ;
In emission stop state before Symbol plurality of projecting portions, by simultaneously detecting the presence or absence of light reception in the light receiving portion of the multiple at the predetermined cycle, and determination means for determining the presence or absence of the interference light,
A light reception timing means for instructing a detection timing of the presence or absence of light reception by the determination means;
If it is determined that there is a light input of the interference light by the determination means, seen including a display means for displaying to that effect,
The light reception timing means performs a round process of sequentially shifting the detection timing by the determination means over the entire phase of the predetermined period until the determination means determines that there is incident light of the mutual interference light . Multi-optical axis photoelectric sensor. Each forms the optical axis of the pair, a plurality have a light-receiving portion and the light projecting unit which operates in synchronism, with the light projecting portion corresponding to the optical axis and the light receiving portion is sequentially synchronized with a predetermined period A multi-optical axis photoelectric sensor that operates ,
And means for stopping the light projection of the light projecting unit of the multiple,
An optical axis selection means for repeatedly selecting each of the plurality of optical axes at a predetermined external diagnostic light-receiving period in the light projection stop state of the plurality of light projecting units;
In emission stop state of the plurality of light projecting portion, by detecting the presence or absence of light reception on the light receiving portion which is selected by the optical axis selection means and determination means for determining the presence or absence of the interference light,
A light reception timing means for instructing a detection timing of the presence or absence of light reception by the determination means;
If it is determined that there is a light input of the interference light by the determination means, seen including a display means for displaying to that effect,
The light reception timing means performs a round process of sequentially shifting the detection timing by the determination means over the entire phase of the light reception period at the time of the external diagnosis until the determination means determines that the mutual interference light is incident. Perform multi-optical axis photoelectric sensor. 4. The multi-optical axis photoelectric sensor according to claim 3, wherein the display unit includes a display unit that displays a selected optical axis that has been determined by the determination unit that the mutual interference light is incident . 5. The photoelectric sensor is provided in a predetermined device, and outputs a signal indicating that a predetermined light-blocking state operation is performed to the predetermined device when the determination unit determines that the mutual interference light is incident. , the signal is the determination means is output until no determination that there is a light input of the interference light, a photoelectric sensor according to any one of claims 1 to 3.

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