JPS6026445B2 - Photo sensor circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a photo sensor circuit, and more particularly, to a photo sensor circuit that stabilizes the output of a photo sensor used as a position signal detector in a positioning device, etc. against changes in temperature, aging, etc. It is.

Generally, a photo sensor 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 decrease by several tens of percent when the temperature changes by several tens of degrees Celsius or changes over time over several thousand hours. fluctuate.

By the way, in a servo-controlled positioning device or the like, a position signal and a speed signal are obtained from the output voltage of a photo sensor circuit, and these signals are used to control the position and speed. In positioning devices and the like, deviations in the output voltages of photo sensor 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 purpose of the present invention was to solve the above-mentioned drawbacks, and to solve the problem of reducing the amount of light due to ambient temperature fluctuations, changes in the light-emitting diode and light-receiving diode during operation, and dirt on the light-emitting surface of the light-emitting diode. It is an object of the present invention to provide a highly reliable photo sensor circuit that stabilizes the output of a photo sensor and allows a positioning device using the photo sensor to work stably. The photo sensor circuit according to the present invention will be described in detail below with reference to the drawings. FIG. 1 shows an embodiment of a photo sensor section according to the present invention.

In FIG. 1a, 1 is a light emitting diode for a light source,
Two signal detection light receiving diodes 2a and 2b are arranged opposite to the light emitting diode. Signals obtained from the signal detection light emitting diodes 2a and 2b are formed to have opposite phases to each other. FIG. 1c shows a structure in which these light receiving diodes 2a and 2b are formed on a monolithic substrate. In the figure, 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. 2a and 2b constituting the light receiving diode 2 formed on the monolithic substrate in this way.
It is thought that the electrical characteristics of each photodetector diode are almost the same. A rotating disk 3 constituting the slit plate of the present invention is arranged between the light emitting diode 1 and the light receiving diode 2. Follow and rotate. 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 3b are formed at equal intervals. The width L in the circumferential direction of the light passing section 3a or the light blocking section 3b and the width L of the diffusion region or the width L between the diffusion regions of the light receiving diode 2a in FIG. are formed to be equal. Light-receiving diode 2b in Fig. 1c
The shape shown in FIG. 1B is made from the fan shape formed by the circumferential width 3L of the light passing portion 3a and the light blocking portion 3b and the center of the disk. The broken line portion in FIG. 1c shows an example where the light passing portion 3a of the rotating disk 3 and the light receiving diode 2 overlap. With the above configuration, when the rotary disk 3 is rotated, it is possible to obtain output signal waveforms of the light receiving diodes 2a and 2b having opposite phases as shown in FIGS. 3a and 3b. The total amount of input light changes depending on the overlap between the light passing section 3a of the rotating disk 3 and the light receiving diodes 2a and 2b, and an output current that changes sinusoidally as shown in Fig. 3a and b is obtained. However, the sum of these waveforms does not change even when the rotating disk 3 is rotated, and remains constant as shown in FIG. 3c. Second
The figure shows a block diagram for explaining one embodiment of a photo sensor circuit according to the present invention. In the figure, 1 is a light emitting diode, 2a and 2b are light receiving diodes, and the signals obtained by these diodes are in opposite phases to each other. Reference numerals 5 and 6 indicate variable gain amplifiers whose gains vary depending on control signals input to terminals 5b and 6b.

5a and 6a are the input terminals of these variable gain amplifiers, and 5c
, 5d, and 6c are output terminals.

7 is an adder, 8 is a constant voltage source that outputs a reference voltage Vref, and 9 is a control circuit that compares the output voltage Vref of the constant voltage source 8 with the output voltage of the adder 7.

The light receiving diodes 2a and 2b are each connected to a variable gain amplifier 5.
, 6, and the output current of each photodiode is amplified by a respective variable gain amplifier. If these variable gain amplifiers 5 and 6 have the same circuit configuration, the same gain can be obtained. The amplified signals amplified by variable gain amplifiers 5 and 6 are outputted to respective output terminals 5c and 6co, and each amplified signal is inputted to input terminals 7a and 7b of adder 7. Since the two signals input to the adder 7 have opposite phases to each other,
The summed signal remains constant regardless of the rotation of the rotating disk (as shown in Figure 3c). The addition signal from adder 7 is
The control circuit 9 compares it with the reference voltage Vref of the constant voltage source 8 . A control signal from this control circuit 9 is input to terminals 5b and 6b of variable gain amplifiers 5 and 6, and the gain is controlled. If the loop consisting of the variable gain amplifiers 5 and 6, the adder 7, and the control circuit 9 is set to negative feedback, the addition signal from the adder 7 will be constant regardless of the input, and the reference voltage Vr will be constant.
It becomes equal to ef. The output currents of the light-receiving diodes 2a and 2b are shown in FIGS. 3a and 3b, but this current level may change due to changes in temperature, etc., which may cause the brightness of the light-emitting diotard 1 to change or the characteristics of the light-receiving diodes 2a, 2b to change. It changes when However, as long as the geometric arrangement remains unchanged, the relative current relationship between the light receiving diodes 2a and 2b remains unchanged. Moreover, the light receiving diodes 2a, 2bo
If they are arranged on the same monolithic substrate, the variation in characteristics will be small, and the characteristics due to temperature, aging, etc. will also change in the same direction, so the relative current relationship will not change. Further, by integrating the detector, reliability is improved, and adjustment between the light receiving diodes when attaching the detector becomes unnecessary, and high attachment accuracy can be easily achieved. Furthermore, the variable gain amplifiers 5 and 6 have the same gain, and the addition signal output from the output terminal 7c of the adder 7 is controlled to be equal to the reference voltage Vref from the constant voltage source 8, so that the variable gain amplifiers 5 and 6 have the same gain. The output terminal 5d of the gain amplifier 5 has the brightness of the light emitting diode 1 and the light receiving diode 2.
A stabilized amplified signal can be obtained regardless of the light receiving characteristics of a and 2b. If this amplified signal is used as a detection signal to control a positioning device or the like, stable operation can be obtained. FIG. 4 shows the variable gain amplifiers 5, 6 shown in FIG.
A specific circuit example of the adder 7 will be shown. In the same figure, OP
1, OP2 is an oven amplifier, R1, R2, R3, R4, R
5, R6 are resistors, Q1, Q2, Q3, Q4, Q5
, Q6 are each PNP transistors. V1, V
2, V3, and V4 are power supplies that provide bias voltages. The terminals in FIG. 4 have the same symbols as the corresponding terminals in FIG. The current DI input to the input terminal 5a is converted to (RI/
R2) is amplified to double the current ○2. PNP transistors Q2, Q3 and resistor R3 are gain adjusters that can change the gain by changing the dividing ratio of currents D3, D5 (D4) depending on the voltage difference between input terminal 5b and V2. variable gain amplifier 6
may be configured so that the same gain as the variable gain amplifier 5 can be obtained. Output current D obtained as above
4. If D6 is made to flow into one end of resistor R4, this voltage becomes 3, which is the sum of the two signals, and adder 7
can be configured. As is clear from the above description, the photo sensor circuit according to the present invention obtains two detection signals having opposite phases from each other from a light receiving element, and adds signals obtained by amplifying these two detection signals by variable gain amplifiers. By comparing the voltage with the voltage and adjusting the gain of the variable gain amplifier so that the amount of deviation becomes 4, the gain from the light receiving element can be adjusted regardless of changes in the light source brightness or the characteristics of the light receiving element due to temperature or changes over time. This is to stabilize the detected signal.

A position detection device using this sensor circuit can easily integrate the light receiving element and the circuit, and has a simple configuration.
Because extremely stable and highly accurate position signals can be obtained under environmental and usage conditions such as temperature and characteristic deterioration, errors in positioning control of servo equipment, etc. can be extremely minimized, and reliability is extremely high. It is easy to assemble and adjust the parts, and the accuracy is improved, making it possible to obtain extremely excellent effects.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram showing an embodiment of a photo sensor section which is a part of a photo sensor circuit according to the present invention, FIG. 2 is a block diagram of an embodiment of the present invention, and FIG. 3 shows each part in FIG. 2. The signal waveform diagram, FIG. 4, is a circuit diagram showing a specific example of the variable gain amplifier and adder in FIG. is a first variable gain amplifier, 6 is a second variable gain amplifier, 7 is an adder, 9 is a control circuit, and Vref is a reference voltage. Figure 1 Figure 3 Figure 2 Figure 4

Claims (1)

[Scope of Claims] 1. A light source; a first light source that receives light from the light source via a slit plate having an optical slit, and outputs a first detection signal as it moves relative to the slit plate; a light receiving element; a first variable gain amplifier that amplifies the first detection signal and outputs an amplified signal; and a first variable gain amplifier that receives light from the light source via the slit plate and that receives the light from the slit plate and moves relative to the slit plate. a second light-receiving element that outputs a second detection signal having an opposite phase to the first detection signal; a second variable gain amplifier that amplifies the second detection signal and outputs an amplified signal; an adder that adds the amplified signal of the first variable gain amplifier and the amplified signal of the second variable gain amplifier and outputs a summed signal; and an adder that compares the summed signal and a reference voltage signal, and 2
and a control circuit that outputs a control signal for adjusting the gain of the first variable gain amplifier, the photo sensor circuit stabilizing the amplified signal of the first variable gain amplifier.