JPS5941147B2 - Cairo - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device for photoelectrically detecting the amount of motion of a moving body, and in particular to a device that automatically sets the output level of a photoelectric detector and can stably perform a detection operation even if the moving body is replaced. Regarding.

For example, in order to detect the rotational speed of a test mark of a power consumption meter, light is irradiated onto the periphery of the test mark and the reflected light is detected.

This test mark is disk-shaped, and a mark attached to a part of its periphery is detected, and a pulse signal is generated by detecting a decrease in the amount of reflected light at this mark part. In this case, in order to prevent erroneous detection of small scratches, etc., the light irradiated to the test specimen should be such that it illuminates a relatively wide area of the test specimen, and the light should be adjusted in response to small changes in the test specimen. Try not to. Therefore, the photoelectric detection output changes slowly around the mark on the test surface. However, when forming a pulse signal using a detection signal that changes slowly in this way, the pulse width etc. of the formed pulse signal will differ depending on the setting of the detection level. Accurate pulse formation has conventionally been considered difficult due to factors such as drift of a capacitor provided for storage. The present invention has been made in view of the above points, and it forms a pulse signal that accurately corresponds to the momentum of a moving body based on a photoelectric detection signal obtained as the moving body moves in a straight line, rotation, etc. The purpose is to provide a circuit that can be obtained.

In order to achieve this object, the present invention counts clock pulses from the time when the output level of a photoelectric detector reaches a predetermined value until the output level reaches a peak value, and based on this counted value, clock pulses are counted. This circuit is configured to set the peak output level of the photoelectric detector by controlling the power supply to the photoelectric detector and changing the output level, thereby forming accurate pulses. An embodiment of the present invention will be described below with reference to the accompanying drawings. FIG. 1 shows an embodiment of the present invention, in which the PD is a photoconductive photoelectric detector made of, for example, CdS or CdSe, and is supplied with constant current by a constant current circuit CC to generate a voltage signal according to optical input. e and comparator circuit C
Give to OMP.

The comparison circuit COMP compares the output e of the photoelectric detector PD with the reference voltage Vs, and provides an output to the gate G when they match. Gate G provides a clock pulse CP to counter C when the output of comparator COMP is applied. Counter C
integrates the clock pulse CP and outputs the counting output as D-A.
It is given to the conversion circuit DA. The DA conversion circuit DA converts the output of the counter C into analog and provides it to the constant current circuit CC.
The constant current circuit CC performs a current control operation according to the output of the DA conversion circuit DA, and when the output becomes constant, performs constant current maintenance control and supplies power to the photodetector PD. FIG. 2 is a characteristic diagram for explaining the detection operation of the circuit of FIG. 1, and the operation of the circuit of FIG. 1 will be explained using this diagram.

Now, let us consider a case where the test target of the watt-hour meter rotates and the output e of the photoelectric detector PD gradually decreases. When the output e decreases and becomes equal to the reference voltage Vs, the comparison circuit COMP provides an output to the gate G, which opens the gate G and provides a clock pulse CP to the counter C. Counter C integrates and counts clock pulses CP and provides a count output to DA converter circuit DA. As a result, the D-A conversion circuit DA gives an analog signal according to the count value of the counter C to the constant current circuit CC, controls the current supplied to the photoelectric detector PD, and keeps the output e of the detector PD constant. hold the value. Then, as the test target rotates, the photoelectric detector PD
Due to the change in the resistance value of , the output e shows a gradual increasing tendency after reaching a minimum value.

Then, when the output e of the photoelectric detector PD no longer matches the reference voltage Vs, the comparator circuit COMP stops the signal being applied to the gate G, and closes the gate G. This results in
No more clock pulses are applied to the counter C, and the count value corresponding to the peak value of the photodetector output is stored in the counter C. Therefore, after this, the output of the counter C is constant and the input/output of the D-A conversion circuit DA is constant, so the constant current circuit CC is connected to the photoelectric detector PD.
A constant current is supplied to the Subsequently, the photodetector PD produces an output e that gradually increases with the rotation of the test specimen. As a result of this operation, a count corresponding to the peak value was stored in the counter C, so from now on, this stored value is used to control the power supply to the photoelectric detector PD via the D-A converter circuit DA and the constant current circuit CC. It can be carried out.

Therefore, since it is no longer necessary to apply clock pulses to the counter C, the clock pulse generating circuit may be disconnected. After that, as the test specimen rotates, the photoelectric detector PD generates an output e whose peak value is at the same level as the reference voltage Vs. When the test target rotates at a constant speed, such as when testing a power meter, the photoelectric detector PD produces an output e that changes at regular intervals. Therefore, by using a slicer that sets a slice level that differs from the reference voltage level by △e,
By processing the output e of the photoelectric detector PD, a pulse voltage can be extracted. This pulse voltage always rises and falls at points that differ from the peak value by a predetermined value Δe. Therefore, the rotation of the test target and the accompanying output of the photoelectric detector always have a constant phase relationship. Next, when testing separate watt-hour meters, the peak value of the output e of the photoelectric detector PD may be different, so the counter C is not shown or the set signal from the set circuit is used. The counter C is then reset and performs the same operation as described above, causing the counter C to store data.

Thereby, the constant current circuit CC performs power supply control such that the peak value of the photoelectric detector becomes the reference voltage level. As described above, the present invention uses a digital circuit to control the power supply circuit so that the output level of the photoelectric detector matches the reference value, and then fixes the digital circuit output. It is possible to provide a pulse forming circuit that is much more stable than the analog fixed circuit used.

In particular, when detecting a low-velocity moving body, conventional circuits tend to generate inaccurate pulses due to the drift of the capacitor that stores the peak value, but such concerns are eliminated.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing one embodiment of the present invention, and FIG. 2 is a characteristic diagram for explaining the operation of the embodiment of FIG. Vs...Reference voltage, CP...Clock pulse.

Claims (1)

[Claims] 1. A photoelectric detector that detects light repeatedly applied in response to the movement of a moving body to be measured, and a comparison circuit that compares the level of the repetitive output voltage including the peak value provided from this detector with a reference voltage. , a clock pulse generator, a counter controlled by the output of the comparator circuit and counting the clock pulses provided from the generator, and a counter that is controlled by the output of the comparator circuit and counts the clock pulses provided from the generator; a reset circuit for once resetting the counter, a digital-to-analog converter for converting the digital output of the counter into an analog output, and a constant current circuit that is controlled by the output of this converter and flows a current to the photoelectric detector. and the output voltage level of the photoelectric detector is determined by the count value of the counter when the peak value that first appears after the counter is reset in the repetitive output voltage matches the reference voltage. A photoelectric detection device that automatically sets the output level.