JP2002204151A - Many optic axes photoelectric sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a many optic axes photoelectric sensor which can accurately detect 'circuit abnormality' at an early stage and detect 'disturbance light abnormality' with optimal sensitivity. SOLUTION: If an output signal SC received from a comparator 13 synchronized with 'an optical signal Y' emitted at non-lighting timing of opposite element, is a signal which shows 'light projected state', a CPU 14 raises an abnormality check flag. In one abnormal scan operation, if an output signal SC with an abnormality flag raised is received and an abnormality flag is not raised in the following output signal SC, it is regarded as 'circuit abnormality' considering that unique abnormality of a photosensitive circuit 12 of a photosensitive element 11 belonging to a certain optical axis L is generated. If the same result is obtained in the following abnormality scan operation, detection operation is performed for 'circuit abnormality'. Meanwhile, in one abnormality scan operation, if an output signal Sc with an abnormality flag raised is received continuously and the same result is obtained in the next two abnormality scan operations, for example, detection operation is performed for 'disturbance light detection'.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plurality of light emitting elements for sequentially emitting light, and a multi-light detecting element for performing a detecting operation based on each light receiving signal from a plurality of light receiving elements facing each of the light emitting elements. The present invention relates to an axial photoelectric sensor, and particularly to detection of disturbance light.

[0002]

2. Description of the Related Art A conventional multi-optical axis photoelectric sensor is disclosed in Japanese Patent No. 3046400. This is because the light receiving signals from the respective light receiving elements are sequentially received at a time when the opposing light emitting element does not emit light (hereinafter referred to as “non-light emitting timing”), and whether the light receiving signal level is equal to or higher than a predetermined level is determined. Is determined. Specifically, the light receiving signal level from each light receiving element at the non-light emitting timing should be a level when light is not received originally. However, as external disturbance light, for example, light emitted from another sensor or a lighting fixture, etc. When strong light from the light enters the light receiving element, the light receiving signal level from the light receiving element may be higher than a predetermined level. Therefore, it is possible to detect "disturbance light abnormality" by determining whether or not the light receiving signal level from each light receiving element at the non-light emitting timing is equal to or higher than a predetermined level. In order to further improve the detection accuracy, the scanning operation is repeated a plurality of times, and the detection of the disturbance light is performed only when the determination result that the light receiving signal level is equal to or higher than the predetermined level for each optical axis continues.

[0003]

In the multi-optical axis photoelectric sensor, the reason why the light receiving signal level becomes equal to or higher than the predetermined level at the non-light emitting timing is not always caused by disturbance light. Factors other than disturbance light include so-called "circuit abnormalities" such as short-circuits between multiple light receiving circuits, failure of an analog switch connected to the light receiving circuit, and failure of the light receiving circuit itself.
In some cases, the light receiving signal level may be higher than a predetermined level at the non-light emitting timing.

However, in the conventional multi-optical axis photoelectric sensor, regardless of whether “abnormal circuit” or “abnormal disturbance light”, when the light receiving signal level at the non-light-projecting timing is equal to or higher than a predetermined value, it is uniform. There is a problem that it is determined to be "abnormal disturbance light". Therefore, in the conventional multi-optical axis photoelectric sensor, when the above-described disturbance light detection operation is performed,
It is also conceivable to avoid the above problem as soon as possible by considering the possibility of “circuit abnormality”. However, in general, the disturbance light detection often ignores the short-time disturbance light and detects the case where the disturbance light intrusion continues for a certain time or more. Therefore, when disturbance light detection is performed by the above-described multiple scans, the number of scans is set to be relatively large. Therefore, "urgent circuit abnormalities"
There is a problem that detection can be performed only at the same timing as that of "abnormal disturbance light" and cannot be detected early.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to detect "abnormal circuit light" accurately and early and to detect "abnormal disturbance light" with optimum sensitivity. It is to provide a multi-optical axis photoelectric sensor.

[0006]

In order to achieve the above object, a multi-optical axis photoelectric sensor according to the first aspect of the present invention has a plurality of light receiving elements provided by opposing a plurality of light emitting elements. An optical axis is configured, a plurality of light emitting elements are sequentially emitted, and a light receiving signal output from the light receiving element is enabled at a light emitting timing of the corresponding light emitting element, and the light receiving element receives light from the light emitting element. In a multi-optical axis photoelectric sensor that determines whether light is incident or not and detects a light blocking state for each optical axis, each signal from a plurality of light receiving elements is transmitted to a light emitting element of the optical axis to which the light receiving element belongs. Inspection timing control means that is activated at a time when light is not emitted, and a light receiving element belonging to one optical axis is in a light incident state based on a light receiving signal from a light receiving element that is activated by the inspection timing control means, and The light-receiving element belongs to Circuit abnormality detecting means for determining that the light receiving element of the optical axis adjacent to the optical axis adjacent to the optical axis is in the light blocking state, and a light receiving signal from the light receiving element activated by the inspection timing control means. And a disturbance light abnormality detecting means for judging an abnormality when a plurality of light receiving elements belonging to an adjacent optical axis are detected to be in a light incident state.

According to a second aspect of the present invention, in the multi-optical axis photoelectric sensor according to the first aspect, the inspection timing control means includes:
The scanning operation for sequentially validating the light receiving signals from each light receiving element for each optical axis is repeated, and both the circuit abnormality detecting means and the disturbance light abnormality detecting means are determined to be abnormal for at least a predetermined number of scans. Operate on condition, and
The feature is that the number of scans at which the circuit abnormality detecting means operates is smaller than that of the disturbance light abnormality detecting means.

[0008]

<Operation and effect of the invention><Invention of claim 1>"Disturbance light abnormality" is generated when strong light from, for example, a lighting device or the like enters the detection area, and such light is generally generated. The light is irradiated to a wide range to some extent, and it is considered that the light is simultaneously incident on not only the light receiving elements belonging to one optical axis but also a plurality of light receiving elements belonging to an adjacent optical axis to exert an influence.
On the other hand, "circuit abnormality" is generally caused by, for example, a failure of an analog switch connected to the light receiving circuit or a failure of the light receiving circuit itself. It is considered extremely rare that the elements cause "circuit abnormality" at the same time. Therefore, according to the configuration of the first aspect, the signal from each light receiving element is detected by the inspection timing control means when the light emitting element belonging to the same optical axis does not emit light (hereinafter referred to as “non-light emitting timing”). Enable). Along with this, the circuit abnormality detecting means detects that the light receiving element belonging to one optical axis is in the light receiving state, and that the light receiving element of the optical axis adjacent to the optical axis to which the light receiving element belongs is in the light blocking state. Sometimes it is judged abnormal. On the other hand, the disturbance light abnormality detecting means determines that an abnormality is detected when it is detected that a plurality of light receiving elements belonging to adjacent optical axes are in a light incident state. That is, the "circuit abnormality" can be detected by the circuit abnormality detection means,
The disturbance light abnormality detecting means can detect the “disturbance light abnormality”.

According to the second aspect of the present invention, the scanning operation by the inspection timing control means is repeated a plurality of times, and both the circuit abnormality detecting means and the disturbance light abnormality detecting means continue for a predetermined number of scans or more. The respective detection operations are performed only when it is determined that there is an abnormality. This gives 1
The detection accuracy is further improved as compared with the case where the detection operation is performed in each scan. Further, the execution interval of the detection operation is shorter in the circuit abnormality detection means than in the disturbance light abnormality detection means. Therefore, the detection of the "circuit abnormality" requiring urgent detection and the "disturbance light abnormality" for which the detection operation is to be performed only when an abnormality is detected for a certain period or more to ignore the so-called instantaneous disturbance light are separately detected. It is possible to do. This makes it possible to accurately and early detect “abnormal circuit” and detect “abnormal disturbance light” with optimal sensitivity.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described with reference to FIGS. The multi-optical axis photoelectric sensor according to the present embodiment includes a light projector 20 and a light receiver 10 which are arranged to face each other. On the side of the light emitter 20 facing the light receiver 10,
For example, four light emitting elements 21 composed of, for example, LEDs are arranged in a line in the vertical direction, and the light
For example, four light receiving elements 11 made of, for example, photodiodes that make a pair with each of the light emitting elements 21
Are also arranged in a line along the up-down direction to form four optical axes L (in FIG. 1, symbols L1, L2, L3, and L4). In this multi-optical axis photoelectric sensor, the “light emission timing” of each light emitting element 21 and the time when each light emitting element 21 does not emit light (hereinafter referred to as “non-light emission timing”).
Then, it is determined whether the light from the light emitting element 21 is incident on each of the light receiving elements 11 belonging to the same optical axis L,
Thus, "detection of an object to be detected", "disturbance light detection", and "circuit abnormality detection" are enabled.

<Electrical Configuration> FIG. 1 shows an electrical configuration of the multi-optical axis photoelectric sensor of the present embodiment. As shown in the figure, the light projector 20 is provided with a light emitting circuit 22 and a CPU 23 to which the light emitting element 21 is connected. The CPU 23 includes a clock pulse signal (hereinafter referred to as “light emission timing signal X”) having a predetermined cycle for generating the “light emission timing” and a clock pulse signal (hereinafter referred to as “non-light emission timing signal Y”) for generating the “non-light emission timing”. "). In the present embodiment, as described later, the “non-light-emission timing signal Y” is sequentially generated immediately before the “light-emission timing signal X”. The light emitting circuit 22 includes a CPU
It operates in response to the "light emission timing signal X" given from the light emitting device 23, and sequentially supplies a drive signal from the light emitting element 21 on the upper end side to the light emitting element 21 on the lower end side of the light projector 20, and repeats this operation. Thereby, light is sequentially emitted from the light emitting element 21 on the upper end side of the light projector 20.

On the other hand, the light receiver 10 amplifies the signal from the light receiving element 11 for each light receiving element 11 and receives a light receiving signal S corresponding to the amount of received light (in each figure, reference numerals S1, S2, S3, S
4) are provided, respectively. The output of each light receiving circuit 12 is, for example, a switch element SW composed of an analog switch (in FIG.
1, SW2, SW3, and SW4) are commonly connected to an input terminal of a comparator 13 that compares an input voltage level with a predetermined reference value, and an output signal SC is provided to an input terminal of a CPU 14. Further, each control terminal of each switch element SW is connected to a signal terminal of a detection shift register 15 and a signal terminal of an abnormality detection shift register 16 which are driven by receiving a drive signal from the CPU. CPU
14 sequentially takes in the “light emission timing signal X” from the CPU 23 on the light projector 20 side, and supplies a drive signal to the detection shift register 15 in synchronization with the “light emission timing signal X”. Further, the CPU 14 also controls the C
The “non-light emission timing signal Y” is sequentially fetched from the PU 23, and a drive signal is supplied to the abnormality detection shift register 16 in synchronization with the “non-light emission timing signal Y”.

As will be described later, the CPU 14 distinguishes the output signal SC output from the comparator 13 in synchronization with the “light emission timing” and the “non-light emission timing”, and outputs the output signal SC at the “light emission timing”. Perform “detection of detected object” based on SC and “non-light emission timing”
"Disturbance light detection" and "circuit abnormality detection" are performed on the basis of the output signal SC at step (1).

Next, the operation of the multi-optical axis photoelectric sensor according to the present embodiment will be described with reference to timing charts shown in FIGS. << Detection of Object to be Detected >> When the power of the multi-optical axis photoelectric sensor is turned on, the light projecting circuit 22 causes the light projecting element 21 on the upper side of the light projector 20 to project light on the lower side, as shown in FIG. The “light emission timing signal X” is sequentially given to the element 21 at the “light emission timing”, so that light is sequentially emitted from the light emitting element 21 on the upper end side of the light projector 20. At the same time, the CPU 14 of the light receiver 20 is
And the drive signal is sequentially supplied to the detection shift register 15 in synchronization with the "light emission timing signal X". The detection shift register 15 receives the drive signal and switches the switch element SW.
1 to the switch SW4 in sequence (hereinafter referred to as “detection signal A (in each figure, reference symbols A1, A2, A3, A4)”).
), And the switch elements SW1 to SW4 are sequentially turned on. More specifically, as shown in FIG. 2, the first light emission timing signal X
In synchronization with this, the detection signal A1 is output from the detection shift register 15, the switch element SW1 is enabled, and the light reception signal S1 is given to the comparator 13 from the light reception circuit 12 of the optical axis L1. Next, in synchronization with the second light emission timing signal X, a detection signal A2 is output from the detection shift register 15, the switch element SW2 is enabled, and thus the light reception signal S from the light reception circuit 12 of the optical axis L2.
2 is given to the comparator 13. Similarly, detection signals A3 and A4 are respectively output in synchronization with the third and fourth light emission timing signals X, and the light reception signals S3 and S4 are sequentially transmitted from the light reception circuit 12 of the optical axes L3 and L4 to the comparator 13. Given. Then, the above operation (hereinafter referred to as “detection scan operation”) is repeated.

The comparator 13 determines whether the light receiving signal S level is equal to or higher than a predetermined reference level, and outputs an output signal SC corresponding to the determination result to the CPU 14.
Given to. Here, the predetermined reference value is set slightly lower than the input voltage level corresponding to the light receiving signal S output from the receiving circuit in a state where the detected object does not exist in the detection area. Therefore, the level of the light receiving signal S is always equal to or higher than the predetermined reference level, and the comparator 13 outputs the output signal SC. However, as shown in the figure, for example, when an object exists between the light projecting element 21 and the light receiving element 11 constituting the optical axis L3 and the light from the light projecting element 21 is blocked, The level of the light receiving signal S3 becomes equal to or lower than the predetermined reference level, and the inverted output signal SC is output from the comparator 13, whereby the "detection of the detected object" operation is executed by the CPU 14.

<< Abnormality Detection >> On the other hand, C
The PU 14 takes in the “non-light-emission timing signal Y” from the CPU 23 of the light projector 20 immediately before the “light-emission timing signal X”, and synchronizes with the “non-light-emission timing signal Y” to shift the abnormality detection shift register 16. Are sequentially supplied with drive signals. The shift register 16 for abnormality detection receives the drive signal and switches from the switch element SW1 to the switch SW4.
, A control signal (hereinafter referred to as “abnormality signal B (indicated by B1, B2, B3, B4 in each drawing)”) is output in sequence to switch elements SW1 to SW4.
Are sequentially turned on. More specifically, as shown in FIG. 3, in synchronism with the first non-light emission timing signal Y, the abnormality detection signal B1 is output from the abnormality detection shift register 16, the switch element SW1 is enabled, and the optical axis L
The light receiving signal S 1 is supplied to the comparator 13 from the light receiving circuit 12 belonging to 1. Next, in synchronization with the second non-light-emission timing signal Y, the abnormality detection shift register 16 outputs the abnormality signal B2, activates the switch element SW2, and thereby receives the light reception signal from the light reception circuit 12 belonging to the optical axis L2. S2 is given to the comparator 13. Similarly, signals B3 and B4 for abnormalities are output in synchronization with the third and fourth non-light emission timing signals Y, respectively.
3, light receiving signals S3, S4 from the light receiving circuit 12 belonging to L4.
Are sequentially applied to the comparator 13 to determine whether the level of the received signal is equal to or higher than a predetermined reference level, and the output signal SC is sequentially applied to the CPU 14. Then, the above operation (hereinafter referred to as “abnormal scan operation”) is repeated. Thus, the time when each light emitting element 21 does not emit light (in this embodiment, immediately before “light emission timing”).
The light receiving element 1 belonging to the same optical axis L as the light emitting element 21
1 can be detected in the “light incident state”.

As described above, the "disturbance light abnormality"
Is generally considered to be simultaneously incident on a plurality of light receiving elements 11 belonging to the adjacent optical axis L and affecting the light receiving element 11, and the "circuit abnormality" is regarded as "disturbance light abnormality". It is extremely unlikely that a plurality of light receiving elements 11 belonging to the circuits cause "circuit abnormality" at the same time. <Circuit Abnormality Detection> Then, if the output signal SC received from the comparator 13 in synchronization with the non-light-emission timing signal Y is a signal indicating the “light-in state”, the CPU 14 sets an abnormality check flag. Then, in one abnormal scan operation, an output signal SC with the abnormality check flag raised is received, but if no abnormality check flag is raised in the output signals SC before and after that, a certain optical axis L is It is regarded as "circuit abnormality" because an abnormality unique to the light receiving circuit 12 of the light receiving element 11 to which it belongs has occurred. Then, in this embodiment, in order to increase the detection accuracy, for example, when the same result is obtained in the next abnormal scan operation, the detection operation of “circuit abnormality” is performed. For example, as shown in FIG.
When an abnormality occurs in the light receiving circuit 12 of the light receiving element 11 belonging to the “light receiving state” and the light receiving circuit 12 enters the “light incident state”, the level of the light receiving signal S3 output from the light receiving circuit 12 is always higher than the predetermined reference level. Therefore, first, the light receiving circuit 12 of the optical axis L2
Does not cause any abnormality, the level of the light receiving signal S2 given at the timing when the abnormality signal B2 is output is lower than the predetermined reference level, and the abnormality check flag is not set. However, since the level of the reception signal S3 transmitted at the timing when the abnormality signal B3 is output is equal to or higher than the predetermined reference level, the abnormality check flag is set. Next, since no abnormality has occurred in the light receiving circuit 12 of the adjacent optical axis L4, the level of the light receiving signal S4 transmitted at the timing when the abnormality signal B4 is output is lower than the predetermined reference level, and the abnormality check flag is set. Absent. At this point, it is determined that the abnormality of the light receiving circuit 12 of the optical axis L3 is not caused by "disturbance light" but is a "circuit abnormality" unique to the light receiving circuit 12. Then, in the next abnormal scan operation, an abnormality check flag is similarly turned on only for the light receiving signal S3 of the optical axis L3, thereby outputting an operation signal indicating "circuit abnormality",
For example, a circuit abnormality detection indicator (not shown) blinks.

<Detection of disturbance light> On the other hand, in one abnormal scan operation, the output signal SC with the abnormal check flag is continuously received, and the same result is obtained, for example, in the next two abnormal scan operations. Sometimes, "disturbance light detection"
Is performed. For example, as shown in FIG. 4, when disturbance light enters the light receiving elements 11 belonging to the three optical axes L1, L2, and L3, the light receiving signals S1, S2, and S3 output from the light receiving circuits 12 are generated. The level is always higher than a predetermined reference level. Therefore, the abnormality signals B1, B2, B3
Are output at the timing of the output of the received signals S1, S2, and S3, respectively. Since the levels of the received light signals S1, S2, and S3 are equal to or higher than a predetermined reference level, an abnormality check flag is set. At this point, the “circuit abnormality” of the specific optical axis L
Instead, "disturbance light detection" is determined. In the second and third abnormal scan operations, the reception signal S
An abnormality check flag is set for S1, S2, and S3, and an operation signal indicating "disturbance light detection" is output to cause, for example, a disturbance light detection indicator (not shown) to blink.

As described above, according to the present embodiment, the light receiving element 11 belonging to one optical axis L in one abnormal scan operation in consideration of the features of “circuit abnormality” and “disturbance light detection”.
Is in a light incident state, and when it is detected that the light receiving element 11 of the optical axis L adjacent to the optical axis L to which the light receiving element 11 belongs is in the light blocking state, a “circuit abnormality” is detected and the adjacent optical axis L When it is detected that the plurality of light receiving elements 11 belonging to the light receiving state are in a light incident state, it is determined as “disturbance light detection” and abnormality detection can be performed.

In addition, since the detection operation is performed when the same abnormality is continuously detected in a plurality of abnormality scan operations for each abnormality detection, the detection operation is performed in one scan. The detection accuracy is improved as compared with. In addition, the number of scan operations is
Is performed twice and “disturbance light detection” is performed three times. Therefore, the detection of the "circuit abnormality" requiring urgent detection and the "disturbance light abnormality" for which the detection operation is to be performed only when an abnormality is detected for a certain period or more to ignore the so-called instantaneous disturbance light are separately detected. It is possible to do.
This makes it possible to accurately and early detect “abnormal circuit” and detect “abnormal disturbance light” with optimal sensitivity.

In the above embodiment, each of the optical axes L1, L
Since the timing of abnormality detection is performed sequentially in synchronization with “non-light emission timing” and is not simultaneous with respect to 2, L3 and L4,
As shown in FIG. 5, when there is momentary disturbance light,
In some cases, disturbance light cannot be detected at the detection timing of the adjacent optical axis L. In this case, the light receiving circuit 12 for one optical axis
It is possible that an abnormality check flag is set only for the light receiving signal S from the camera. However, if the "circuit abnormality" is caused by the instantaneous disturbance light as described above, by performing the detection operation by performing the scanning operation twice or more times as in the above embodiment, The abnormality check flag is not set in all the abnormal scan operations. Therefore, it is possible to avoid a problem that the detection operation is erroneously performed as “circuit abnormality”.

<Other Embodiments> The present invention is not limited to the embodiments. For example, the following embodiments are also included in the technical scope of the present invention. Various changes can be made without departing from the scope of the invention. (1) In the above embodiment, the detection operations of “circuit abnormality” and “disturbance light detection” are respectively performed after the abnormal scan operation twice and three times. However, the present invention is not limited to this. May be performed after the abnormal scan operation. By appropriately setting the number of times, the detection accuracy can be arbitrarily adjusted for each of “circuit abnormality” and “disturbance light detection”.

(2) In the above embodiment, the multi-optical axis photoelectric sensor is constituted by the four optical axes L1, L2, L3, and 4. However, if it is constituted by a plurality of optical axes, ,
It may be more or less than four.

(3) In the above embodiment, the “non-light-emission timing” is immediately before the light-emission timing of each light-emitting element 21. However, the present invention is not limited to this. It is sufficient that the light emitting element 21 constituting the optical axis is not emitting light.

(4) Unlike the above embodiment, a configuration may be adopted in which a plurality of switch elements SW are simultaneously enabled at each non-light emitting timing. This makes it possible to more instantaneously cope with the instantaneous disturbance light.

[Brief description of the drawings]

FIG. 1 is an electrical configuration diagram of a multi-optical axis photoelectric sensor according to an embodiment of the present invention.

FIG. 2 is a timing chart for explaining “detected object detection”;

FIG. 3 is a timing chart for explaining “circuit abnormality” detection;

FIG. 4 is a timing chart for explaining “disturbance light detection”.

FIG. 5 is a timing chart for explaining a case where momentary disturbance light is incident.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 ... Light receiving element 13 ... Comparator 15 ... Detection shift register 16 ... Abnormality detection shift register 21 ... Light emitting element A1, A2, A3, A4 ... Detection signal B1, B2, B3, B4 ... Abnormality signal 14 ... CPU L1, L2, L3, L4: Optical axis S1, S2, S3, S4: Received signal SC: Output signal SW1, SW2, SW3, SW4: Switch element X: Light emission timing signal

Claims (2)

[Claims] A plurality of light receiving elements are provided in opposition to a plurality of light emitting elements so that a plurality of optical axes are formed, and the plurality of light emitting elements sequentially emit light, and a plurality of light axes are emitted from the light receiving elements. The output light receiving signal is enabled at the light emission timing of the corresponding light emitting element, and it is determined whether or not light from the light emitting element is incident on the light receiving element, and the light blocking state of each optical axis is detected. Inspection timing control means for validating each signal from the plurality of light receiving elements when the light emitting element of the optical axis to which the light receiving element belongs does not emit light; Based on the light receiving signal from the light receiving element activated by the means, a light receiving element belonging to one optical axis is in a light-in state, and a light receiving element in an optical axis adjacent to the optical axis to which the light receiving element belongs is blocked. In state Circuit abnormality detecting means for determining that an abnormality has occurred when the light is detected, and a plurality of light receiving elements belonging to adjacent optical axes are in a light-in state based on a light receiving signal from the light receiving element validated by the inspection timing control means. A multi-optical axis photoelectric sensor, comprising: a disturbance light abnormality detecting means for judging an abnormality when it is detected that there is an abnormality in the optical axis. 2. The inspection timing control means repeats a scanning operation for sequentially validating light receiving signals from the light receiving elements for each optical axis, and both the circuit abnormality detecting means and the disturbance light abnormality detecting means are provided. The method according to claim 1, wherein the operation is performed on the condition that it is determined that the abnormality has continued for a predetermined number of scans or more, and the number of scans at which the circuit abnormality detection means operates is smaller than that of the disturbance light abnormality detection means. The multi-optical axis photoelectric sensor according to the above.