JPS5952974B2 - Photo sensor circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a method for stabilizing a photosensor circuit, specifically, a method for stabilizing the output of a photosensor used as a position signal detector in a positioning device, etc. against changes in temperature, aging, etc. It is related to the method.

Generally, a photosensor consists of a combination of a light-emitting diode and a light-receiving diode, but if the current of the light-emitting diode is constant, the output of the light-receiving diode will change over a temperature change of several tens of degrees Celsius or a change over time of several thousand hours. fluctuates by several tens of percent.

Incidentally, in a servo-controlled positioning device or the like, a position signal and a speed signal are obtained from the output voltage of a photosensor circuit, and these signals are used to control the position and speed.

In positioning devices and the like, deviations in the output voltages of photosensor circuits used to control position and speed appear as deviations in position signals and speed signals. This deviation disrupts the operation of control systems such as positioning devices, which are designed to minimize the control deviation, which is the difference between the set value and the control amount transmitted via the detector, etc., and the original function is not achieved. I won't be able to do it.
The present invention has been made in order to eliminate the above-mentioned drawbacks, and is aimed at stabilizing the output of the photosensor against changes in ambient temperature, changes over time in the light emitting diode and light receiving diode, etc., and uses the photosensor. The purpose of the present invention is to provide a highly reliable photosensor circuit in which a positioning device, etc. that operates stably.

In order to achieve such an object, the photosensor circuit according to the present invention compares the signal from the compensation light-receiving element with a reference voltage, applies feedback so that the deviation value is minimized, and uses the feedback amount to This is to stabilize the signal from the signal detection light receiving element. A photosensor circuit according to the present invention will be described below with reference to the drawings.

FIG. 1 shows an embodiment of the photosensor section according to the present invention.

In FIG. 1a, 1 is a light emitting diode for a light source, and two light receiving diodes 2a and 2b are arranged opposite to the light emitting diode 1. In FIG. 2a and 2b are a signal detection light receiving diode and a compensation light receiving diode, respectively.

FIG. 1C shows a structure in which these light receiving diodes 2 are formed on a monolithic substrate. In FIG. 1C, the shaded area is a photodetector, and for example, a P-type diffusion region is formed in the shaded area on an N-type Si substrate. The light receiving diode 2 formed on the monolithic substrate in this way is
The electrical characteristics of each photodetector diode a and 2b are as follows:
Ho・゛It is thought that they are the same. A rotating disk 3 serving as a detection body is arranged between the light emitting diode 1 and the light receiving diode 2, and this rotating disk 3 is attached to the shaft 4 of a motor (not shown) and rotates following the rotation of the motor. . As shown in FIG. 1b, the rotating disk 3 has a disk shape, and optical slits are provided on its circumference by etching, and light passing portions 3a and light blocking portions are formed at equal intervals. 3b, and the width 1 in the circumferential direction of the light passing part 3a or the light blocking part 3b, and the width 1 of the diffusion region part of the signal detection light receiving diode 2a of FIG. 1C or the width between the diffusion regions. 1 is formed so that it is equal to 1. The compensating light receiving diode 2b in FIG. 1C has a fan-shaped shape formed by the sum 21 of the circumferential widths of the light passing section 3a and the light blocking section 3b in FIG. 1B and the center of the disk. Make it as shown in the same figure. Qin 1 diagram C
The broken line is an example of the overlap between the J rotating disk 3 and the light receiving section 2. When the rotating disk 3 is rotated with the above configuration,
Current waveforms of the light receiving diodes 2a and 2b as shown in FIG. 2 can be obtained. The light-receiving diode 2a for signal detection is obtained by the overlap between the light passage section 3a of the rotating disk 3 and the diffusion region of the light-receiving diode 2a for signal detection. The total amount of light transmitted changes, and as shown in FIG. 2a, a detection signal consisting of an output current that changes sinusoidally in response to the rotational movement of the rotating disk 3 is obtained.

Further, the total amount of light hitting the compensation light receiving diode 2b does not change even if the rotating disk 3 is rotated, and the output current is constant as shown in FIG. 2b. A constant value comparison signal is obtained. FIG. 3 shows an embodiment of the present invention.

In the figure, 1 is a light emitting diode, 2 is a light receiving diode, and 2a and 2b are a signal detection light receiving diode and a compensation light receiving diode, respectively.

5 and 6 are first and second variable amplification amplifiers whose gains change depending on the signals applied to gain control terminals 7 and 8.

9 and 10 are input terminals of these amplifiers 5 and 6, respectively;
11 and 12 are output terminals of these amplifiers 5 and 6.

13 is a constant voltage source, 14 is the output voltage of the constant voltage source 13 and the second
This is a comparator that compares the output voltages of the variable amplification amplifier 6.

The output current of the compensation light receiving diode 2b is amplified by the second variable amplification amplifier 6, and an output current is outputted to the terminal 12. This signal is compared with the output voltage of constant voltage source 13 by comparator 14 . The output voltage of this comparator 14 is
It is applied to the gain control terminal 8 of the second variable amplification amplifier 6 to control the gain. If the loop composed of the second variable gain amplifier 6 and the comparator 14 is configured to provide negative feedback, the output voltage of the second variable gain amplifier 6 will be independent of the input current value. The output voltage of the comparator 14 is constant and equal to the output voltage of the constant voltage source 13.
is applied to the terminal 7 of the variable amplification amplifier 5. Each of the variable amplification amplifiers 5 and 6 has the same circuit configuration, and when the same voltage is applied to the terminals 7 and 8, the same gain can be obtained. The output currents of the light-receiving diodes 2a and 2b are shown in FIG. 2, but this current level changes when the brightness of the light-emitting diode 1 changes due to changes in temperature, etc., or when the light-receiving diode 2 deteriorates. . however,
As long as the geometric arrangement remains unchanged, the relative current relationship between the light receiving diodes 2a and 2b does not change even if the brightness of the light emitting diodes changes. Moreover, the light receiving diodes 2a, 2
If b is placed on the same monolithic substrate, then
The variation in characteristics becomes smaller, and the characteristics due to temperature, changes over time, etc. also change with the same tendency, so the relative current relationship does not change. Further, by integrating the detector, reliability is improved, adjustment between the light receiving diodes becomes unnecessary when installing the detector, and accuracy can be easily achieved. Since the variable amplification amplifiers 5 and 6 have the same gain, and the output voltage of the second variable amplification amplifier 6 is controlled to be equal to the output voltage of the constant voltage source 13,
At the output terminal 11 of the variable intensification amplifier 5, a stabilized signal that is independent of the luminance of the light emitting diode and the sensitivity of the light receiving diode can be obtained.

FIG. 4 shows a specific circuit example of each variable amplification amplifier 5, 6.

In the same figure, ]5 is an operational amplifier, 16, 17 and 18
are resistors, and their low resistance values are R1, R2, and R3. 19, 20 and 21 are PNP transistors, respectively.

22 and 23 are power supplies that provide bias voltages, respectively;
These are assumed to be provided in common to each of the variable amplification amplifiers 5 and 6 in FIG. 3 (not shown in FIG. 3).

The terminals in FIG. 4 have the same symbols as the corresponding terminals in FIG. Current 11 applied to input terminal 9 or 10
is amplified by the operational amplifier 15 and the PNP transistor 19 to a current 12 which is R1/R2 times.

This current is made 1 by the PNP transistors 20 and 21.
3 and 14. This shunt ratio is determined by the gain control terminal 7
Or it changes depending on the voltage applied to the gain control terminal 7 or 8, and when the voltage applied to the gain control terminal 7 or 8 increases with the bias power supply 23 as a reference, the current 14 decreases and is applied to the gain control terminal 7 or 8. It increases as the voltage decreases. Since the output voltage is R3l4, the gain of this circuit will vary depending on the voltage applied to gain control terminal 7 or 8.
As is clear from the above description, according to the present invention, changes in the light source brightness and characteristics of the light receiving element due to changes in temperature, changes over time, etc. are compared with a reference voltage, and feedback is applied so that the amount of deviation is minimized. Since the gain of the signal detection amplifier is adjusted by the amount of feedback, a stable and accurate position signal can be obtained as an output regardless of changes in light source brightness, light receiving element characteristics, etc.

In the position signal detection according to the present invention, it is easy to integrate the light receiving element and the circuit section, and with a simple configuration, the position signal can be extremely stable and highly accurate against environmental conditions such as temperature and deterioration, and usage conditions. As a result, errors in positioning control of servo equipment, etc. can be made extremely small, reliability is very high, and the detector mechanism can be easily assembled and adjusted, improving accuracy, making it possible to obtain extremely excellent effects. can.

[Brief explanation of drawings]

FIG. 1a is a schematic diagram showing one embodiment of the photo sensor section used in accordance with the present invention, FIGS.
3 is a block diagram showing an embodiment of the present invention, and FIG. 4 is a circuit diagram showing an embodiment of the variable amplification amplifier in FIG. 3. . 1... Light emitting diode, 2a... Light receiving diode for signal detection, 2b... Light receiving diode for compensation, 3... Rotating disk, 4... ...Motor shaft, 5...First variable amplification amplifier, 6
...Second variable amplification amplifier, ]3...
- Constant voltage source, 14... Comparator.

Claims (1)

[Claims] 1. A light-receiving element for signal detection that receives light from a light source that is passed through and blocked by the operation of the detection object and outputs a detection signal according to the operation of the detection object, the gain of which is adjusted by an external signal,
A first amplifier receives the detection signal of the signal detection light receiving element and outputs an output signal, and receives light from the light source that is passed through and blocked by the operation of the detection object and outputs a comparison signal having a constant value. a compensation light-receiving element, a second amplifier whose gain is adjusted by an external signal, which receives a comparison signal from the compensation light-reception element and outputs a comparison output signal; A photosensor circuit comprising a control circuit that compares a reference signal with a reference signal and uses the signal as an external signal for the first and second amplifiers.