JP2004320372A - Photoelectric sensor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a photoelectric sensor device having excellent handleability capable of simplifying a wiring work by realizing automatic regulation of a photodetecting sensitivity in response to an aging photodetecting level change, and eliminating the necessity of grasping an operating state and instructing a sensitivity regulation. <P>SOLUTION: The photoelectric sensor device includes a light emitting unit and a photodetector for forming a predetermined optical path. The photoelectric sensor device photodetects the light emitted from the light emitting unit or its reflected light by the photodetector, and detects the optical state in the optical path from the photodetecting level or more concretely the invasion of an object. The photoelectric sensor device further includes a comparator for comparing the photodetecting level of the photodetector with a predetermined threshold value to output a signal showing the presence or absence of the object, and a calibrating means for calibrating the threshold value according to the photodetecting level by the photodetector at timing of elapsing a predetermined time from the rise and/or fall timing of the signal output from this comparator. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention is directed to an optical state in an optical path formed between the light emitting device and the light receiving device based on a change in a light receiving level of light emitted from the light emitting device by the light receiving device. The present invention relates to a photoelectric sensor device for detecting
[0002]
[Related background art]
The photoelectric sensor device including the light emitter and the light receiver includes a transmission type and a reflection type. The transmission type photoelectric sensor device basically has a light emitter (light emitter) and a light receiver (light receiver) facing each other at a predetermined distance, and an optical path formed between the light emitter and the light receiver. When an object enters the interior, the object detection is performed by utilizing the fact that the light reception level (light reception amount) of the light emitted from the light projector by the light receiver changes.
[0003]
In addition, the reflection type photoelectric sensor device is provided with a light emitter (light emitter) and a light receiver (light receiver) aligned with their optical axis directions, and detects light reflected from an object of light emitted from the light emitter with the light receiver. In this way, object detection is performed. That is, this reflection type photoelectric sensor has no intensity of light reflected by an object when there is no object on the optical axis, and when there is an object on the optical axis, the intensity (light reception amount) according to the distance to the object. ) Is configured to detect an object by using the reflected light of (1) (for example, see Patent Documents 1 and 2).
[0004]
Such a photoelectric sensor device that detects the optical state in the optical path formed between the light emitter and the light receiver as a change in the amount of light received by the light receiver (light reception level) can be used for various purposes such as object detection and object determination. Used for applications. Note that the optical state in the optical path refers to not only the reflectance and transmittance of light on the detection target, but also its shape, as well as the amount of light transmission (propagation) depending on the distance to the detection target. Point.
[0005]
[Patent Document 1]
JP-A-5-308268 [Patent Document 2]
Japanese Patent Application Laid-Open No. Hei 9-116411
[Problems to be solved by the invention]
By the way, in this type of photoelectric sensor device, for example, the light receiving by the light receiving device is caused by the deterioration of the characteristics of the light emitting device or the light receiving device over time, the change of the optical characteristics due to the contamination of the detection target, and the brightness of the background. It cannot be denied that the level gradually decreases. Such a phenomenon is generally referred to as a decrease in the sensitivity of the photoelectric sensor. Therefore, conventionally, as disclosed in Patent Documents 1 and 2, the light receiving sensitivity of the photoelectric sensor is calibrated under predetermined conditions. Specifically, the calibration of the light receiving sensitivity is performed by adjusting a light receiving level determination threshold (threshold) that changes depending on whether an object is present or not according to the light receiving level at that time. The light receiving sensitivity may be adjusted by adjusting the gain of the sensing amplifier or adjusting the amount of light emitted from the light projector.
[0007]
By the way, in the conventional photoelectric sensor device, a control signal for sensitivity adjustment (calibration) is provided from the outside remotely, exclusively called remote tuning. In order to realize such remote tuning, a pair of power supply lines for supplying operating power to the photoelectric sensor device, an output line for outputting an object detection signal, and a control line for remote control are provided. 4 core cables are connected.
[0008]
However, when a large number of photoelectric sensor devices are provided at various sites such as factories and the like, even if the number of connections per photoelectric sensor device is as small as four, it is necessary to perform many connections as a whole. It is unavoidable that the connection work takes a lot of trouble and time. In addition, it is necessary to individually give an auto-tuning command (control signal) at an appropriate timing while grasping the operation status of each photoelectric sensor device. In addition, there is a problem that it is very troublesome to grasp the operation status of each photoelectric sensor device.
[0009]
The present invention has been made in view of such circumstances, and its purpose is to simplify the connection work, and to automatically adjust the light receiving sensitivity according to the deterioration of the characteristics of the projector and the receiver over time. It is an object of the present invention to provide a photoelectric sensor device excellent in handleability, which can make it unnecessary to grasp the operation state and to issue a command for sensitivity adjustment by properly setting.
[0010]
[Means for Solving the Problems]
In order to achieve the above object, a photoelectric sensor device according to the present invention includes a light emitter and a light receiver that form a predetermined optical path, and receives light emitted from the light emitter or reflected light thereof by the light receiver and receives the light. The optical state in the optical path from the level, specifically, to detect the intrusion of an object into the optical path and the like,
A comparator that outputs a signal indicating the presence or absence of the object by comparing the light reception level of the light receiver with a predetermined threshold,
Calibration means for calibrating the threshold value in accordance with the light receiving level of the light receiver at a timing when a predetermined change of the signal output from the comparator is exhibited, for example, at a timing when a certain time has elapsed from the rising and / or falling timing. It is characterized by having.
[0011]
That is, the photoelectric sensor device according to the present invention includes a comparator that compares the light reception level of the light receiver with a predetermined threshold and outputs a signal indicating the presence or absence of the object, and the rising and falling of the output signal of the comparator. // Attention is paid to the fact that the light receiving level by the light receiver is stable at a timing when a certain time has elapsed from the falling timing.
A light receiving level of the light receiver is detected at a timing when a predetermined time has elapsed from a rising and / or falling timing of the output signal of the comparator, and a threshold (detection sensitivity) given to the comparator is automatically determined according to the light receiving level. It is characterized by being calibrated dynamically. Specifically, the rising and / or falling timing of the output signal of the comparator is delayed for a predetermined time, and the threshold (detection sensitivity) is reset at the delayed timing based on the light receiving level of the light receiver. It is characterized by having.
[0012]
According to the photoelectric sensor device configured as described above, it is not necessary to externally grasp the operation state of the photoelectric sensor device, and it is not necessary to externally issue a sensitivity adjustment command. Since there is no need to externally issue an instruction for sensitivity adjustment, the number of core wires to be connected to the photoelectric sensor device is determined by, for example, a pair of power lines for supplying the operating power and an output line for outputting an object detection signal. Therefore, it is possible to reduce the burden of the connection work. If the detection signal is output by changing the impedance between a pair of power supply lines, and the power supply line is also used as a signal output line, the number of core wires is further reduced to reduce the burden of connection work. Can be further reduced.
[0013]
It is preferable that the calibrating means include a calibration control means for judging a stable state of the light receiving level of the light receiver and prohibiting the threshold value calibrating process when the light receiving level is unstable. If the light reception level is unstable, calibration (readjustment) of the threshold is stopped, and the object detection (determination of the light reception level) may be performed using the threshold that has already been set.
[0014]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, a photoelectric sensor device according to an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 shows a schematic configuration of a main part of a photoelectric sensor device according to this embodiment, wherein 1 is a light projector formed of a light emitting diode (LED) that emits laser light having a wavelength of 660 nm, for example, and 2 is the laser light or This is a light receiver including a photodiode (PD) that receives the reflected light. The light projector 1 and the light receiver 2 may constitute a reflection type photoelectric sensor, or may constitute a transmission type photoelectric sensor.
[0015]
Here, it is assumed that light is directly projected from the light projector 1 to a predetermined object detection target area, and that the light receiver 2 directly receives light from the object detection target area. Alternatively, the light may be projected onto a predetermined object detection target area via the optical disc, and the light from the object detection target area may be received via an optical fiber (not shown).
[0016]
The light receiver 2 outputs a signal of a level corresponding to the intensity (received light amount) of the received light, and the output signal (received light level) is a preamplifier circuit (head) including a frequency selection filter (not shown). After being amplified via an amplifier, the signal is converted into a digital signal via an AD converter 3 and is taken into a signal processing circuit 4 composed of a microcomputer or the like, for example, every 200 μsec. The signal processing circuit 4 basically compares the judgment threshold value T set in the memory 5 with the light receiving level R of the light receiving device 2 provided from the AD converter 3 and compares the object in the object detection target area. Is provided with a level determiner (comparator) 6 that outputs a determination signal indicating the presence or absence of. A determination signal from the level determiner (comparator) 6 is externally output as a detection signal from the photoelectric sensor device. The setting unit 9 has a role of setting operating conditions in the photoelectric sensor device, such as a delay time Td described later and a time for determining the stability of the light receiving level R.
[0017]
The level determiner (comparator) 6 outputs an [L] level signal when the received light level R exceeds the determination threshold T, and outputs an [H] level signal when the received light level R falls below the determination threshold T, for example. It has a function to output signals. When importance is placed on the stability of the light reception level R, the level judgment unit (comparator) 6 outputs a signal of the [L] level when the light reception level R exceeds the judgment threshold T for a predetermined time, When the light receiving level R is lower than the determination threshold T for a predetermined time, an [H] level signal may be output. Conversely, when the light reception level R is higher than the determination threshold T, a [H] level signal is output, and when the light reception level R is lower than the determination threshold T, a [L] level signal is output. Of course, it is also possible to configure the comparator (comparator) 6.
[0018]
In the photoelectric sensor device having such a basic function, the present invention (embodiment) is characterized in that the rising timing or the falling timing of the output of the level determiner (comparator) 6 is set to a predetermined time Td. And a calibration circuit 8 that receives the delay output and resets (calibrates) the determination threshold T. The delay circuit 7 may be such that the output of the level determiner (comparator) 6 is delayed as it is for a certain time Td in hardware, but in terms of software, for example, the level determiner ( Any circuit that detects the rising and / or falling edge of the output of the comparator 6 and applies a trigger pulse to the calibration circuit 8 after a predetermined time Td from the edge detection timing may be used.
[0019]
On the other hand, when the above-described trigger pulse is given, the calibration circuit 8 determines, for example, a level of 75% thereof according to the light receiving level (output value of the AD converter 3) R by the light receiving unit 2 at that time, and determines the determination threshold T. And registers it in the memory 5 to update the determination threshold T. Then, the determination threshold T is automatically calibrated so that the updated determination threshold T is used for the subsequent determination of the light reception level R (auto calibration).
[0020]
Specifically, as shown in FIG. 2, when the rise of the light receiving level is detected, the calibration circuit 8 is triggered at a timing delayed from the detection timing by a predetermined time Td to calibrate the determination threshold T. I have. The timing at which the predetermined time Td has elapsed from the rising timing of the light receiving level R is a state where the light receiving level R has sufficiently risen and the level is stable. In other words, the delay time Td is set in consideration of the time required for the light receiving level R to rise and reach a sufficiently stable state. Then, the calibration circuit 8 detects the light reception level R in a stable state, and calibrates the determination threshold T according to the light reception level R. The process of calibrating the determination threshold T is repeatedly performed each time a rising of the light receiving level is detected. Therefore, when the light receiving level R gradually decreases with a change over time, the determination threshold T is also gradually reduced and corrected as the light receiving level R decreases.
[0021]
However, if the light reception level R changes across the determination threshold T before the delay time Td elapses, the delay circuit 7 that measures the delay time Td does not trigger the calibration circuit 8 Reset. As a result, the delay circuit 7 returns to the time-waiting state, and waits until the next timing at which the light receiving level R exceeds the determination threshold T.
[0022]
When it is necessary to set the determination threshold T in consideration of the light receiving level R when the light receiving amount of the light receiving unit 2 is low, for example, the timing at which the detection timing of the falling of the light receiving level is delayed by a certain time Td The light receiving level Rlow detected in the step (1) is stored. Thereafter, when the light receiving level Rhigh is detected at a timing delayed by a predetermined time Td from the detection timing of the rise of the light receiving level, the determination threshold value is determined in accordance with the light receiving levels Rhigh and Rlow. T may be set.
[0023]
Thus, according to the photoelectric sensor device having such an automatic calibration function of the determination threshold T, the output threshold of the detection signal indicating the presence or absence of an object is used, and the determination threshold T is automatically adjusted according to the light receiving level obtained at that time. Since the calibration is performed dynamically, there is no need to externally provide a control signal for calibrating the determination threshold. Therefore, since it is not necessary to connect a control line for supplying a control signal to the photoelectric sensor device from the outside, the number of core wires to be connected to the photoelectric sensor device can be reduced because the control line is not required. . For this reason, the connection burden on the photoelectric sensor device can be reduced.
[0024]
In addition, since the above-described automatic calibration function of the determination threshold T is provided, the operation state of the photoelectric sensor device is externally monitored, and the sensitivity of the photoelectric sensor device is adjusted (calibration of the determination threshold) according to the operation state. Need not be provided. Therefore, the monitoring load on the photoelectric sensor device can be eliminated, and the work load of providing the control signal to the photoelectric sensor device at an appropriate timing is also eliminated each time, so that the ease of use can be significantly improved. It becomes possible. In particular, at a factory site or the like, since many such photoelectric sensor devices are often provided in parallel, for example, over 100 units, the burden of the connection work performed by the above-described automatic calibration function in such a use environment is reduced. The effect of this is enormous. The photoelectric sensor device having the automatic calibration function described above is extremely useful particularly when a plurality of products having the same shape are conveyed side by side at equal intervals and conveyed on a belt conveyor moving at a constant speed. .
[0025]
By the way, for example, when the detection cycle of the light reception level by the light receiver 2 is sufficiently shorter than the cycle of the intrusion of an object into the optical path formed by the light projector 1 and the light receiver 2, the light reception by the calibration circuit 8 is performed. The fluctuation of the light receiving level may be monitored for a certain period after a predetermined time has elapsed from the timing of detecting the rise and / or fall of the level. Then, as shown in FIG. 3, the fluctuation amount of the light receiving level is determined (step S1). If the fluctuation amount is large, the above-described calibration processing of the determination threshold T is prohibited (step S2). It is preferable to include a calibration control unit that permits execution of the calibration process for T (step S3).
[0026]
By the way, regarding the detection of the fluctuation amount of the light reception level described above, for example, the peak value and the bottom value of the light reception level are detected at a certain time after a lapse of a predetermined time from the detection timing of the rise and / or the fall of the light reception level, respectively. It may be determined whether or not the difference between these detection values is large. Alternatively, the average value of the light receiving level in the certain period is obtained, and it is determined whether or not the difference between this average value and the peak value or the bottom value of the light receiving level in the certain period is large to determine the magnitude of the amount of variation. May be. Specifically, for example, when the light receiving level R by the light receiver 2 is sequentially detected at a short sampling cycle of about 200 μSec, the average value of the light receiving level R and the variation thereof are obtained over a period of about 10 to 20 mSec. What is necessary is just to determine the stability of the light receiving level by obtaining the quantity.
[0027]
If control means is provided for executing the calibration process of the determination threshold T in this manner, when the light reception level R by the light receiver 2 is in an unstable state, the determination threshold T is set based on the unstable light reception level R. Problems such as calibration can be avoided. Therefore, the reliability of the determination threshold value T, which is necessary for the object detection, is not impaired, and it is possible to always perform highly reliable object detection.
[0028]
Note that the present invention is not limited to the above-described embodiment. For example, as light used for object detection, not only the above-described LED light but also visible light or infrared light emitted from a lamp can be used. Further, here, the light receiving level of the light receiver 2 is converted into a digital signal and the signal processing is performed. Also, the delay time Td from the rising or falling timing of the light receiving level may be determined according to the detection use of the object, and it is sufficient if the delay time Td can be preset in the photoelectric sensor device. is there. In addition, the present invention can be variously modified and implemented without departing from the gist thereof.
[0029]
【The invention's effect】
As described above, according to the photoelectric sensor device according to the present invention, the timing at which a predetermined change in the light receiving level is exhibited, specifically, the timing delayed by a certain time with reference to the rising and / or falling timing of the light receiving level Since the light receiving level at that time is detected and the determination threshold for the light receiving level for object detection is automatically calibrated, that is, the detection sensitivity is automatically calibrated, so that the light receiving level is not affected by the temporal variation. Without this, stable object detection can always be performed. Moreover, since there is no need to externally provide a control signal for adjusting the detection sensitivity, it is not necessary to monitor the operation state of the photoelectric sensor device, and the number of core wires to be connected to the photoelectric sensor device can be reduced. In addition, a great effect in practical use can be achieved, such as a great reduction in the connection work load.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of a main part of a photoelectric sensor device according to an embodiment of the present invention.
FIG. 2 is a diagram showing a calibration timing of a determination threshold in the photoelectric sensor device shown in FIG.
FIG. 3 is a diagram showing a form of execution / prohibition control of a threshold value calibration process according to the amount of fluctuation of the light receiving level according to the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Projector 2 Receiver 3 AD converter 4 Signal processing circuit (microcomputer)
5 memory (judgment threshold)
6 level judgment device (comparator)
7 delay circuit 8 calibration circuit 9 setting means

Claims (2)

A photoelectric sensor device comprising a light emitter and a light receiver forming a predetermined optical path, and receiving light emitted from the light emitter or its reflected light by the light receiver and detecting an optical state in the optical path from a light receiving level thereof. So,
A comparator that outputs a signal indicating the presence or absence of the object by comparing the light reception level of the light receiver with a predetermined threshold,
A photoelectric sensor device comprising: a calibration unit configured to calibrate the threshold value according to a light receiving level of the light receiver at a timing when a predetermined time has elapsed from a timing at which a predetermined change of a signal output from the comparator is exhibited. . 2. The photoelectric sensor device according to claim 1, wherein the calibration unit includes a calibration control unit that determines a stable state of a light reception level of the light receiver and prohibits a calibration process of the threshold when the light reception level is unstable. 3.

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