JPS63286715A - Automatic output controller for optical sensor - Google Patents

Abstract

PURPOSE:To stabilize the projecting quantity and the photodetecting quantity without exerting damage on the service life of a projector, and also, to prevent a variation of the photodetecting quantity from being suppressed, by providing a circuit for limiting the amplitude of a signal, on an output side of a second automatic output control (APC) circuit. CONSTITUTION:A projector 2, a monitor circuit 4, the first APC circuit 6 and a projector driving circuit 7 form a first negative feedback loop, and on the other hand, the projector 2, a photodetector 3, a photodetecting circuit, a second APC circuit 12 and the projector driving circuit 7 form a second negative feedback loop. Accordingly, an APC device operates as a light quantity stabilizing circuit provided with a double negative feedback loop. In such a state, first of all, the projecting quantity and the photodetecting quantity are stabilized by these negative feedback loops. When the photodetecting quantity is stabilized, It is remains as it is, a variation of the photodetecting quantity containing the information of a surface state is also suppressed simultaneously, therefore, in such double negative feedback loops, the second one contains an amplitude limiting circuit 13 or a gradient limiting circuit 14 of a signal in its loop. In such a way, an amplitude exceeding a prescribed value or a signal variation exceeding a prescribed speed is not suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an automatic output control circuit for stabilizing tt in an optical sensor having a light emitter and a light receiver.In the present invention, the APC circuit refers to an automatic output control circuit. represents. The optical sensor is, for example, an optical large flaw sensor.

Conventional technology Optical sensors that inspect the surface condition of objects to be measured emit light of a certain intensity from a projector, receive the light reflected or transmitted from the object, and analyze changes in the amount of light received. to determine the surface condition. If the amount of light is not stable, not only will accurate measurements not be possible, but when measuring the surface condition of an object with large optical noise, such as a polished surface, the amount of received light will be greatly disturbed, making it difficult to determine abnormal areas. Complex processing is required, processing time is long, and processing equipment is complex.

Therefore, basically, the amount of light emitted and the amount of light received must be stable.

Negative feedback technology is used to stabilize the light intensity in reflective or transmissive optical sensors, in which case the light from the emitter is detected by a monitor receiver placed near the emitter, and the detected light is The drive output of the projector is controlled according to the amount. :l! In particular, even without providing a monitor light receiver, similar control can be performed according to the amount of light detected by the original light receiver. These techniques are disclosed in, for example, JP-A-59-52889 or JP-A-61-19204.
It is described in Publication No. 4.

Problems to be Solved by the Invention When controlling the amount of light using a monitor receiver installed on the projector side, the amount of emitted light can be controlled to be constant, but the amount of received light changes significantly depending on the surface reflectance or transmittance of the object to be measured. This makes accurate measurement difficult. For example, in the case of a distance sensor that triangulates the distance to a measured object based on the receiving position of reflected light from the surface of the measured object, such fluctuations in the amount of received light significantly reduce measurement accuracy.

On the other hand, when detecting the amount of light using the original light receiver, the actual amount of light emitted by the projector cannot be monitored, so depending on the state of the object to be measured, the amount of light emitted may increase abnormally, shortening the life of the projector.

Even if the amount of light is stabilized using negative feedback technology, information representing changes in the surface state of the object to be measured must not be suppressed at the same time.

The purpose of the present invention is to
It is an object of the present invention to provide an automatic output control device for an optical sensor that stabilizes the amount of light emitted and the amount of received light and does not suppress changes in the amount of received light that represent changes in the surface condition of an object to be measured.

Means for Solving the Problems The present invention provides an optical sensor having a light emitter and a light receiver, which includes a monitor circuit including a diagonal monitor receiver for detecting the amount of light emitted by the light emitter, and a monitor circuit that detects the amount of light emitted from the light emitter in accordance with the amount of light emitted by the monitor circuit. A first APC circuit that controls the drive output of the drive circuit, a light receiving circuit that detects the amount of light received by the light receiver, and a second APC circuit that controls the drive output of the projector drive circuit in accordance with the amount of light received by the light receiving circuit. The premise is an automatic output control device for an optical sensor equipped with a circuit.

In such a device, this object is achieved according to the invention as follows. That is, a circuit for limiting the amplitude of the signal is provided on the output side of the second APC circuit.

The same objective can also be achieved by providing a circuit for limiting the slope of the signal on the output side of the second APC circuit.

Furthermore, the same objective can be achieved by providing both a circuit for limiting the amplitude of the signal and a circuit for limiting the slope on the output side of the second APC circuit. In this case, it is expedient to connect the circuit for limiting the amplitude of the signal and the circuit for limiting the slope in series. However, both circuits may be connected in parallel.

Here, the circuit that limits the amplitude of a signal is, for example, a limiter, which limits signals that exceed or fall below a predetermined level, or both. - The circuit for limiting the slope of the force signal is, for example, a low-pass filter or an integrator.

The working projector, the monitor circuit, the first APC circuit, and the projector drive circuit form a so-called first negative feedback loop,
- The left emitter, the light receiver, the light receiving circuit, the second A10 circuit and the emitter drive circuit form a second negative feedback loop. The automatic output control device according to the invention therefore acts as a sight stabilizing circuit with double negative feedback loops, so that first of all these negative feedback loops stabilize the amount of light emitted and the amount of light received.

If the amount of received light is stabilized, changes in the amount of received light that contain information about the surface state will also be suppressed, so the second of these double negative feedback loops including a circuit that limits the amplitude or slope of
As a result, amplitudes greater than a predetermined value or signal changes greater than a predetermined speed are not suppressed.According to the present invention, since the occurrence of these large amplitudes or the occurrences of high-speed changes is determined to be an abnormality on the surface, the apparatus according to the present invention In this case, surface abnormalities can be clearly determined.

DESCRIPTION OF THE EMBODIMENTS The illustrated embodiment shows an example in which the present invention is applied to a distance sensor that measures the distance between the sensor and the object 1 by a so-called triangular aIJ quantity method. Also, here, it is possible to simultaneously inspect the surface of the object to be measured 1 for flaws.

The sensor is provided with a light emitter consisting of a laser element 2 and a light receiver consisting of a position detection element 3 facing the object to be measured. A monitor light receiver is arranged near the laser element 2 to receive and take part of the laser beam, and this monitor light receiver consists of a photo diode 4.

In the embodiment shown in the figure, the output of the photodiode 4 is:
The signal is supplied to the first A10 circuit via an amplifier (not shown). Here, the first A10 circuit is simply configured as a differential amplifier 6, and the light emission reference voltage vR1 is supplied to the other input terminal of this differential amplifier. The output of the differential amplifier 6 is the load addition port i? 35 first input terminals.

Most of the laser light hits the object to be measured 1 and is reflected here to reach the position sensing element 3. The position sensing element 3 has two output terminals, and when the light hits the center of the position sensing element 3, the two output terminals The output terminals produce the same output, and one output terminal produces a larger output than the other depending on the position of the light. So-called triangulation is thereby possible. In other words, the output of one output terminal is
1. If the output of the other output terminal is V2, (Vl-V
2)/(vl-+v2) can be used as distance data. Further, V1+V2 is light amount data, which is used to inspect the surface of the object to be measured 1 for flaws.

In order to perform the above calculation, the output of the position detection element 3 is supplied to the calculation circuit 10 via amplifiers 8 and 9, respectively.

At this time, since the output of the position detection element is supplied as a current value, the amplifier 8.9 performs current-voltage conversion, and a predetermined calculation is performed in the calculation circuit 10 to determine the distance and surface flaw. The results are displayed on a display (not shown).

The outputs of the amplifiers 8.9 are summed in a summing circuit 11 and fed to a second A10 circuit, which also comprises a differential amplifier 12. It is clear that the addition may be performed in the arithmetic circuit 10 in this case. The differential amplifier 12 adds
A difference between the X voltage and the received light amount reference voltage VR2 is formed. According to the embodiment shown in FIG. 1, this difference is supplied to the second and third input terminals of the load summing circuit 5, on the one hand via the amplitude limiting circuit 13 and on the other hand via the slope limiting circuit 14. Ru.

In this embodiment, the amplitude limiting circuit 13 is composed of two limiters having an upper limit value and a lower limit value, but may be composed of one limiter having a lower limit value, for example.

On the other hand, the slope limiting circuit 14 is composed of a low-pass filter, but it is clear that it may be configured as an integrator, for example.

The load addition circuit 5 is supplied with the output of the first differential amplifier 6 supplied to the first input terminal, the output of the amplitude limiting circuit 13 supplied to the second input terminal, and the third input terminal. The output of the slope limiting circuit 14 is added as an appropriate ratio. At that time, by appropriately selecting this ratio, two +i
'The feedback rate of the rFA loop can be appropriately selected, and
For example, if the weight of the signal supplied to the second or third input terminal is O, a device having only one of the amplitude limiting circuit 13 and the gradient limiting circuit 14 is realized.

The output terminal of the load addition circuit 5 is connected to the control input terminal of a floodlight drive circuit 7, which includes a differential amplifier 6, an amplitude limiting circuit 13, and a gradient limiting circuit 14.
The laser element 2 is driven depending on the output of the .

In the embodiment shown in FIG. 2, the amplitude limiting circuit 13 and the slope υj limiting circuit 14 are connected in series. Therefore, differential amplification n12
The output terminal of is connected to the second input terminal of the load addition circuit 5'' via an amplitude limiting circuit 13 and a slope limiting circuit 14.Other points are the same as the embodiment shown in FIG. The embodiment shown in FIG. 2 is more sensitive to abnormal signals than the embodiment shown in FIG. 1.Which one is to be applied can be selected depending on the conditions.

9h Song According to the automatic output control device according to the present invention, the amount of light emitted and the amount of light received by the optical sensor can be significantly stabilized, and the life of the projector is not adversely affected.

In the case of reflective sensors, minute scratches and surface abnormalities can be detected even on objects with poor surface roughness (polished surfaces, cast surfaces, etc.), objects with changing surface color, A1 constant objects with curved surfaces, etc. It is possible to simplify and speed up the flaw discrimination process.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a first embodiment of an automatic output control device according to the present invention, and FIG. 2 is a block diagram showing a part of the second embodiment.

Claims (3)

[Claims] (1) In an optical sensor having a light emitter and a light receiver,
A monitor circuit including a monitor receiver for detecting the amount of light emitted by the light emitter, a first APC circuit that controls the drive output of the emitter drive circuit according to the amount of light emitted by the monitor circuit, and a light receiver that detects the amount of light received by the light receiver. A second APC circuit is provided for controlling the drive output of the emitter drive circuit according to the amount of light received by the circuit and the light receiving circuit, and a circuit for limiting the amplitude of the signal is provided on the output side of the second APC circuit. An automatic output control device for an optical sensor, characterized by: (2) In an optical sensor having a light emitter and a light receiver,
A monitor circuit including a monitor receiver for detecting the amount of light emitted by the light emitter, a first APC circuit that controls the drive output of the emitter drive circuit according to the amount of light emitted by the monitor circuit, and a light receiver that detects the amount of light received by the light receiver. A second APC circuit is provided for controlling the drive output of the emitter drive circuit according to the amount of light received by the circuit and the light receiving circuit, and a circuit for limiting the slope of the signal is provided on the output side of the second APC circuit. An automatic output control device for an optical sensor, characterized by: (3) In an optical sensor having a light emitter and a light receiver,
A monitor circuit including a monitor receiver for detecting the amount of light emitted by the light emitter, a first APC circuit that controls the drive output of the emitter drive circuit according to the amount of light emitted by the monitor circuit, and a light receiver that detects the amount of light received by the light receiver. and a second APC circuit that controls the drive output of the emitter drive circuit according to the amount of light received by the light receiving circuit, and a circuit that limits the amplitude of the signal and a signal An automatic output control device for an optical sensor, characterized by being provided with a circuit that limits the slope.