JPH08292260A - Photoelectric sensor having self-diagnostic function - Google Patents

Abstract

PURPOSE: To generate a self-diagnosis signal without fail irrespective of the speed of movement of an object of detection when a light reception level is in an unstable region. CONSTITUTION: Light is projected into a monitoring space from a light-emitting element 11 and a reflected light on an object l is received by a photodetector 21. When a light reception level in the photodetector 21 is in an unstable region wherein it is higher than a stable light-interception level and lower than a stable light-entrance level, a self-diagnosis signal is outputted from a self- diagnostic circuit 30. The self-diagnostic circuit 30 delivers rectangular wave signals which show a first output value outputted when the light reception level in the photodetector 21 is the stable light-interception level or below or the stable light-entrance level or above and a second output value being different from the first output value repeatedly and alternately in a set period, and it generates the first output value at the time point when the light reception level enters the unstable region.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is such that the level of light received by the light receiving means is such that circuit operation is possible, but it is not possible to guarantee whether or not detection of an object or distance measurement to the object is normally performed. At the same time, the present invention relates to a photoelectric sensor having a self-diagnosis function for notifying that the output result is not always guaranteed.

[0002]

2. Description of the Related Art Generally, a photoelectric sensor receives light from a monitoring space with a light receiving element, detects the presence or absence of an object in the monitoring space based on the amount of light received by the light receiving element and the light receiving position, and even detects the object. It is configured to calculate the distance of.
This kind of photoelectric sensor operates stably when the amount of light received by the light receiving element is sufficient, but even if the light receiving level of the light receiving element falls within the range where circuit operation is possible when the light receiving level of the light receiving element decreases. There arises a problem that the operation becomes unstable and the reliability of the output result decreases. This kind of phenomenon is caused by optical elements (lenses, etc.) and photoelectric elements (projectors,
It may be caused by the deviation of the optical axis of the light receiving element), dirt, or the like, and may also be caused by the distance to the object or the reflectance or transmittance of the object. On the other hand, if ambient light is present even when there is no object in the monitoring space, the light-receiving level of the light-receiving element becomes high and circuit operation becomes possible, resulting in some output result. Such a problem occurs regardless of whether it is an active type that projects light from the photoelectric sensor to the monitoring space or a passive type that does not project light.

Further, as the photoelectric sensor, a light beam is projected onto the surveillance space, and the triangulation method is applied based on the reflected light from the object in the surveillance space, or the time difference from the projection to the reception is calculated. There is also provided a photoelectric sensor that obtains the distance to an object by obtaining a corresponding amount. In some photoelectric sensors of this type, a detection output is obtained when the object is within a predetermined distance range. Even with such a photoelectric sensor that calculates the distance, the distance cannot be accurately calculated if the amount of received light is insufficient, and the distance is erroneously recognized if there is ambient light when there is no object. there's a possibility that.

Therefore, when the light receiving level of the light receiving element is within a range where the circuit operation is possible but the reliability of the output result is low, the optical element or the photoelectric element may be deteriorated or the optical axis is deviated. It is considered that the self-diagnosis signal is generated by determining that it is an unstable region in which the target object cannot be accurately detected or the distance to the target object cannot be accurately determined.

For example, in the structure shown in FIG. 5, the level at which some detection output is obtained by the output of the light receiving element is set as the operation level La, and the stable light shielding level Ld and the operation level La which are lower than the operation level La by a predetermined ratio. The stable light input level Lb is set to be higher by a predetermined ratio. If the light receiving level at the light receiving element is below the stable light blocking level Ld or above the stable light receiving level Lb, it is determined that the light receiving level is in the stable region and accurately reflects the presence or absence of detection of the object, On the other hand, the light receiving level is stable and the light blocking level is L.
When it is higher than d and lower than the stable light input level, the light receiving level is in the unstable region, and it is judged that the presence or absence of the detection of the object is not accurately reflected, and the self-diagnosis signal is output. Specifically, when the light receiving level is in the unstable region, the predetermined time T
If it continues for 1 (for example, 0.3 seconds) or more, a self-diagnosis signal is output as shown in FIG. 5 (b) after a certain time T1 from the time of entering the unstable region, and immediately after the light receiving level goes out of the unstable region. It is designed to cancel the self-diagnosis signal. This configuration can be used regardless of active type or passive type.

Further, in the case of an active type photoelectric sensor which projects pulsed light by a control signal as shown in FIG. 6C and receives reflected light or transmitted light in synchronization with the pulsed light, FIG.
As shown in (a), a stable light shielding level Ld and a stable light incident level Lb are set for the operation level La, and the light receiving level of one of the pulse light generation period and the non-generation period is the stable light shielding level. If it is an unstable region between Lb and the stable light input level Lb, the number of times the light receiving level of the light receiving element becomes the unstable region is counted as shown in FIG. For a specified number of times (for example,
When it occurs 7 times), there is a configuration in which a self-diagnosis output is generated.

[0007]

In the former case, since the fixed time T1 is fixedly set, as shown in the right end of FIG. 5, the detected object is stably entered in a time shorter than the fixed time T1. When passing between the light level Lb and the stable light blocking level Ld, the self-diagnosis signal may not be generated even though the light receiving level of the light receiving element passes through the unstable region. For example, in a moving object, the light receiving level changes with time, and thus it may not be possible to detect passage through an unstable region.

Further, in the latter conventional configuration shown in FIG. 6,
In the case where the change of the detection state does not occur for a long time, the abnormality cannot be output unless the change occurs a predetermined number of times, so that the discovery of the abnormality may be delayed and the device may be seriously damaged. Furthermore, in the photoelectric sensor of the type that measures the distance, if the reflectance of the moving detection object at the position where the light beam is radiated changes, the detection light level of the detection object existing within the predetermined distance range will be a marginal light amount. The level may not be exceeded, and even if the distance to the detected object is within the range in which the detection output should be generated, it may be erroneously determined to be abnormal (unstable region).
If the margin light amount level is lowered so as to avoid such an erroneous determination, it becomes impossible to accurately detect the decrease in the light emission amount of the light beam and the contamination of the optical element (lens).

The present invention has been made in view of the above reasons, and its object is not only when the detected object is stopped, but also when the detected object is moving, the light receiving level is unstable. It is an object of the present invention to provide a photoelectric sensor having a self-diagnosis function that can surely generate a self-diagnosis signal regardless of the moving speed of a detected object in a region.

[0010]

According to a first aspect of the present invention, there is provided a photoelectric sensor provided with a light receiving means for receiving light from a monitoring space and a processing means for detecting an object based on an output of the light receiving means. First comparing means for comparing the stable light-shielding level set below the minimum light-receiving level at which the object can be detected with the light-receiving level with the light-receiving means, and the light-receiving level sufficient for the processing means to detect the object. Second comparing means for comparing the stable light input level set above with the light receiving level of the light receiving means, and the self comparing device during the period when the light receiving level of the light receiving means is higher than the stable light blocking level and lower than the stable light receiving level. A self-diagnosis circuit for outputting a diagnostic signal, wherein the self-diagnosis circuit outputs a first output value and a first output value when the light-receiving level at the light-receiving means is below the stable light-shielding level or above the stable light-receiving level. The output value a rectangular wave signal that repeats alternately a set cycle time and different second output value,
The first output value is generated at the start of the period.

According to a second aspect of the present invention, in the first aspect of the invention, there is provided a cycle adjusting means for adjusting the cycle of the self-diagnosis signal output from the self-diagnosis circuit. The invention according to claim 3 is based on the light projecting means for projecting the light beam into the monitoring space, the light receiving means for receiving the reflected light of the light beam by the object existing in the monitoring space, and the reflected light received by the light receiving means. Distance calculating means for calculating the distance to the object existing in the monitoring space, minimum light amount determining means for comparing the light receiving level of the light receiving means with the minimum level that can be calculated by the distance calculating means, and the light receiving means of the light receiving means. A margin light amount determining means for comparing the light receiving level with a margin level at which the distance can be stably calculated by the distance computing means, and a light receiving level at the light receiving means is judged to be higher than the minimum level by the minimum light amount judging means and a margin light amount is judged. The self-diagnosis circuit outputs a self-diagnosis signal during a period determined by the means to be lower than the margin level, and the self-diagnosis signal has a light-receiving level at the light-receiving means that is equal to or lower than the minimum level. A rectangular wave signal that alternately repeats a first output value and a second output value that is different from the first output value at a set cycle, when the margin level is exceeded, at the start time of the period. Then, the first output value is generated.

According to a fourth aspect of the present invention, in the third aspect of the invention, there is provided a cycle adjusting means for adjusting the cycle of the self-diagnosis signal output from the self-diagnosis circuit.

[0013]

According to the first and third aspects of the invention, the first output value and the first output value output when the light receiving level of the light receiving means is below the stable light blocking level or above the stable light receiving level. A rectangular wave signal that alternately repeats a second output value different from the output value in a set cycle is output as a self-diagnosis signal,
The first output value is generated when the light receiving level enters the unstable region which is higher than the stable light blocking level and smaller than the stable light receiving level. Therefore, when the light receiving level enters the unstable region, the first output value similar to the stable region is generated. The second output value is generated after a time determined according to the cycle of the rectangular wave signal has elapsed, and then the rectangular wave signal is continuously output during the period when the light receiving level is in the unstable region. Therefore, when the optical element (lens or the like) or the photoelectric element (light emitting element, light receiving element) becomes dirty or deteriorates, or the optical axis is deviated, the self-diagnosis signal can be output to the outside. If the notification is performed using the self-diagnosis signal, it is possible to notify the abnormality of the photoelectric sensor or the abnormality of the device using the photoelectric sensor.
When there is no abnormality, if the light receiving level does not reach the second output value even after passing through the unstable region for a short time, the same first output value as in the stable region is generated. In a normal use condition without a signal, the self-diagnosis signal is not generated unnecessarily.

Further, according to the third aspect of the invention, since this configuration is adopted in the distance measuring type photoelectric sensor, when the self-diagnosis signal is generated, the amount of light sufficient to accurately measure the distance is obtained. It is possible to know that there is no such thing, and it is possible to take measures to accurately measure the distance to the detected object. According to the configurations of claims 2 and 4, since the cycle adjusting means for adjusting the cycle of the self-diagnosis signal output from the self-diagnosis circuit is provided, the cycle of the self-diagnosis signal is adjusted according to the moving speed of the detected object. By setting the cycle according to the state of the detected object, it is possible to generate the self-diagnosis signal regardless of the moving speed of the detected object and notify the abnormality.

[0015]

【Example】

(Embodiment 1) In this embodiment, as shown in FIG. 1, detection light is emitted from a light emitting element 11 composed of an LED or a semiconductor laser through a light projecting lens 12 into a monitoring space to detect an object 1 in the monitoring space. By detecting the reflected light through the light receiving lens 22 by the light receiving element 21 such as a photodiode,
A photoelectric sensor that detects the presence or absence of an object in the surveillance space is illustrated. The light emitting element 11 sends out pulsed light to the monitoring space by being supplied with timing pulses of a constant cycle output from the timing generation circuit 13 through the drive circuit 14. Further, the output of the light receiving element 21 is input to the light amount determination circuit 24 through the amplifier circuit 23. Light amount determination circuit 24
Then, by using the timing pulse output from the timing generation circuit 13, synchronous detection in synchronization with the pulsed light from the light emitting element 11 is performed, and the output of the light receiving element 21 when the light emitting element 11 is projecting and when not projecting. To extract. Further, the light quantity determination circuit 24 is set with a stable light-shielding level that is lower by a predetermined ratio and a stable light-incident level that is higher by a predetermined ratio than the operation level described in the prior art, and the light emitting element 11 is not projected. The light receiving level during light is compared with the stable light blocking level, and the light receiving level during light projection is compared with the stable light incident level. That is, the light amount determination circuit 2
Reference numeral 4 includes a first comparing means and a second comparing means.

The comparison result of the light receiving level and the stable light shielding level is latched by the stable light shielding level discrimination data latch circuit 31 in synchronization with the timing pulse, and the comparison result of the light receiving level and the stable light receiving level is converted into a timing pulse. The data is latched by the stable light incident level determination data latch circuit 32 in synchronization. Further, the light receiving level is compared with the operation level in the operation level determination circuit 33, and if the light receiving level is equal to or higher than the operation level, it is determined that a detection object exists in the monitoring space, and a detection signal is output to the output circuit 34.

Stable light shielding level discrimination data latch circuit 31
The output result of the stable light-incident level determination data latch circuit 32 is self-diagnosed as a binary signal of H level (power supply voltage) and L level (0 V) through the stable light-shielding determination circuit 35 and the stable light-incident determination circuit 36, respectively. It is input to the circuit 30. The self-diagnosis circuit 30 is a circuit that outputs a rectangular wave signal of a predetermined cycle that alternately repeats H level and L level as a self-diagnosis signal, and the light reception level is higher than the stable light shield level by the output of the stable light shield determination circuit 35. The self-diagnosis signal is generated when it is shown to be high and when the output of the stable incident light determination circuit 36 indicates that the received light level is lower than the stable incident light level. Further, the cycle of the self-diagnosis signal can be adjusted by the oscillation cycle adjusting means (variable resistor or the like). The self-diagnosis signal is generated from the time when it becomes equal to or higher than the stable light shielding level or becomes equal to or lower than the stable light incident level. ). Therefore, the change as the self-diagnosis signal occurs after a half cycle of the self-diagnosis signal (the duty ratio of the self-diagnosis signal is set to 50% for simplification of description). The self-diagnosis signal is output to the outside through the output circuit 37. When the stable light input level is exceeded, the LED drive circuit 51 is used to turn on the indicator lamp 52 formed of a light emitting diode.

According to the above construction, as shown in FIG. 2, the light receiving level is equal to or higher than the stable light receiving level Lb or the stable light blocking level L.
When d is less than or equal to (stable region), no self-diagnosis signal is generated, which is lower than the stable light incident level Lb and stable light shielding level Ld.
When it is higher than that (unstable region), a self-diagnosis signal is output as shown in FIG. When the light receiving level changes from the unstable region to the stable region, the self-diagnosis signal stops immediately. Since the cycle of the self-diagnosis signal is variable, if an appropriate cycle is set according to the moving speed of the object to be detected, as shown in the right end portion of FIG. Even if it crosses, while preventing unnecessary self-diagnosis signal from being output, if the received light level is in an unstable region, by outputting the self-diagnosis signal in a short time, the detected object moves at a relatively high speed. It is possible to generate the self-diagnosis signal even when there is.

(Embodiment 2) This embodiment basically has the same structure as that of the first embodiment, but the object 1 is used as a photoelectric sensor.
2 shows a distance-measuring-type photoelectric sensor that measures a distance up to and generates a detection output when the object 1 is within a predetermined distance range. That is, as shown in FIG. 3, a position detecting element (PSD, two photodiodes arranged in the longitudinal direction, etc.) 21 'is used as a light receiving element. The position detecting element 21 ′ of this type includes a light receiving lens 22.
The two current signals whose ratio changes according to the position of the light spot formed on the light receiving surface are output. Both current signals are input to the position determination circuit 26 through the current-voltage conversion circuits 25a and 25b, respectively. In the position discriminating circuit 26, the distance to the detection object 1 is obtained based on both signals, and it is determined whether or not the distance is within a preset distance range. That is, the position determination circuit 26 functions as distance calculation means. This determination result is the position determination data latch circuit 4
Latched to 1. In addition, one of the outputs of the two signals (generally, the signal with the smaller signal value) is used as the light amount determination circuit 2
It is input to 7 and compared with the minimum level and the margin level in synchronization with the timing pulse. That is, the minimum level is compared with the received light amount when the light emitting element 11 is not projecting light, and the margin level is compared with the light projecting period of the light emitting element. Since one output of the position detecting element 21 'reflects the amount of received light, if the amount of received light is above a margin level at which distance measurement can be accurately performed or below a minimum level at which distance measurement is impossible. As long as the amount of received light is in the stable region, the reliability of the detection output can be guaranteed. Further, when the amount of received light is larger than the minimum level and smaller than the margin level, the self-diagnosis signal is output because it is in the unstable region. As described above, the light amount determination circuit 27 is also used as the first comparing means and the second comparing means.

The comparison result between the received light amount and the minimum level in the light amount determination circuit 27 is the minimum level determination data latch circuit 42.
The result of comparison with the allowance level is latched by the allowance level determination data latch circuit 43. It is shown by the position discrimination data latch circuit 41 that the distance to the detected object 1 is within the set distance range, and the output of the minimum level discrimination data latch circuit 42 causes the received light amount to be equal to or higher than the minimum level required for distance measurement. When it is indicated that, the object presence / absence determining circuit 44 determines that the detected object 1 exists within the set distance range and outputs a detection output to the output circuit 45.

When the margin discriminating circuit 46 determines that the amount of received light is equal to or larger than the margin level according to the data latched in the margin level discriminating data latch circuit 43 and the detection signal is output from the object presence / absence discriminating circuit 44, the LED Through the drive circuit 51, an indicator lamp 52 including a light emitting diode
Light up. When the margin determination circuit 46 does not generate the detection output from the object presence / absence determination circuit 44 and the margin level determination data latch circuit 43 determines that the received light amount does not exceed the margin level, the received light amount is equal to or less than the minimum level. It is determined that there is, and the indicator lamp 52 is turned on at this time as well.
When the amount of received light is determined to be less than or equal to the margin level in the margin determination circuit 46 and the object 1 is detected by the object presence / absence detection determination circuit 44, the amount of received light is equal to or greater than the minimum level, and therefore the self-diagnosis circuit 40 performs self-diagnosis The signal is output to the output circuit 47. The self-diagnosis diagnostic signal is the same as that shown in the first embodiment, and is a rectangular wave signal in which 0 V and the power supply voltage are alternately repeated. The self-diagnosis circuit 40 is provided with an oscillation cycle adjusting means (variable resistor or the like) 48 so that the cycle of the self-diagnosis signal can be adjusted. After all, the self-diagnosis signal is generated when the received light amount is above the minimum level and below the margin level. Other configurations and operations are the same as those of the first embodiment.

The above-described structure enables the operation shown in FIG. That is, FIG. 4A shows the distance to the detected object 1, and the position determination circuit 26 determines whether the distance is close (upper side) or far (lower side) with respect to the set value DL. In the object presence / absence detection determination circuit 44, the detected object 1 is set to the set value DL based on this result.
When it is closer than that, the detection output as shown in FIG. Further, in the light amount determination circuit 27, the received light amount is compared with the minimum level Ll and the margin level Lr as shown in FIG. As described above, if the amount of received light is equal to or greater than the minimum level Ll or the margin level Lr, the indicator lamp 5 as shown in FIG.
Turn on 2. On the other hand, in the unstable region where the received light amount is larger than the minimum level Ll and smaller than the margin level Lr, and the detection output is generated, the self-diagnosis signal is generated as shown in FIG. 4 (e). is there.

[0023]

According to the first and third aspects of the present invention, the first output value and the first output value output when the light receiving level of the light receiving means is equal to or lower than the stable light shielding level or higher than the stable light incident level. When a rectangular wave signal that alternately repeats a second output value different from the above is output as a self-diagnosis signal as a self-diagnosis signal, and when the received light level is higher than the stable light-shielding level and smaller than the stable light-receiving level, it enters an unstable region. Since the first output value is generated, the first output value similar to that in the stable region is generated at the time when the light receiving level enters the unstable region, and after the time determined according to the cycle of the rectangular wave signal elapses. The second output value is generated, and thereafter, the rectangular wave signal is continuously output during the period in which the light receiving level is in the unstable region, and the optical element (lens or the like) or the photoelectric element (light emitting element, light receiving element) is contaminated. ,deterioration,
When an abnormality such as a deviation of the optical axis occurs, there is an advantage that a self-diagnosis signal can be output to the outside to immediately notify the abnormality. When there is no abnormality, if the light receiving level does not reach the second output value even after passing through the unstable region for a short time, the same first output value as in the stable region is generated. In a normal use condition without a signal, the self-diagnosis signal is not generated unnecessarily.

Further, according to the invention of claim 3, since this structure is adopted in the distance measuring type photoelectric sensor, if the self-diagnosis signal is generated, the amount of light sufficient to accurately measure the distance is not obtained. It is possible to take a measure so that the distance to the detected object can be accurately measured. Since the invention according to claims 2 and 4 includes the cycle adjusting means for adjusting the cycle of the self-diagnosis signal output from the self-diagnosis circuit, the cycle of the self-diagnosis signal can be adjusted according to the moving speed of the detected object. By setting the cycle according to the state of the detected object, there is an advantage that the self-diagnosis signal can be generated to notify the abnormality regardless of the moving speed of the detected object.

[Brief description of drawings]

FIG. 1 is a block diagram showing a first embodiment.

FIG. 2 is an operation explanatory diagram of the first embodiment.

FIG. 3 is a block diagram showing a second embodiment.

FIG. 4 is an operation explanatory diagram of the second embodiment.

FIG. 5 is an operation explanatory diagram of a conventional example.

FIG. 6 is an operation explanatory diagram of another conventional example.

[Explanation of reference numerals] 1 detection object 11 light emitting element 12 light emitting lens 21 light receiving element 22 light receiving lens 24 light amount determination circuit 26 position determination circuit 27 light amount determination circuit 30 self-diagnosis circuit 33 operation level determination circuit 38 oscillation cycle adjusting means 40 self-diagnosis Circuit 44 Object presence / absence determination circuit 46 Margin determination circuit 48 Oscillation cycle adjusting means

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location H03K 17/78 9108-2F G01S 17/88 A

Claims (4)

[Claims] 1. A photoelectric sensor having a light receiving means for receiving light from a monitoring space and a processing means for detecting an object based on an output of the light receiving means, wherein a minimum light receiving level at which the processing means can detect the object. A first comparing the stable light shielding level set below with the light receiving level of the light receiving means
Comparing means, the second comparing means for comparing the light receiving level at the light receiving means with the stable light receiving level set above the light receiving level sufficient for the processing means to detect the object, and the light receiving at the light receiving means. It has a self-diagnosis circuit that outputs a self-diagnosis signal during a period when the level is higher than the stable light-shielding level and lower than the stable light-incident level. A rectangular wave signal that alternately repeats a first output value and a second output value that is different from the first output value at a light incident level or higher at a set cycle, and starts the above period. A photoelectric sensor having a self-diagnosis function, which is characterized by generating a first output value at a time point. 2. The photoelectric sensor having a self-diagnosis function according to claim 1, further comprising a cycle adjusting means for adjusting a cycle of a self-diagnosis signal output from the self-diagnosis circuit. 3. A light projecting means for projecting a light beam into a monitoring space, a light receiving means for receiving reflected light of the light beam by an object existing in the monitoring space, and monitoring based on the reflected light received by the light receiving means. Distance calculating means for calculating the distance to the object existing in the space, minimum light amount determining means for comparing the minimum level that can be calculated by the distance calculating means and the light receiving level of the light receiving means, and the distance calculating means for calculating the distance. A margin light amount determination means for comparing the margin level that can be stably calculated with the light reception level at the light receiving means, and a self-diagnosis signal that outputs a self-diagnosis signal when the light reception level at the light receiving means is higher than the minimum level and lower than the margin level The self-diagnosis signal is different from the first output value and the first output value output when the light-receiving level of the light-receiving means is below the minimum level or above the margin level. A photoelectric sensor having a self-diagnosis function, which is a rectangular wave signal which alternately repeats the following second output value at a set cycle, and generates the first output value at the start of the period. 4. A photoelectric sensor having a self-diagnosis function according to claim 3, further comprising cycle adjusting means for adjusting a cycle of a self-diagnosis signal output from the self-diagnosis circuit.