JPH04184202A - Position detector - Google Patents

Abstract

PURPOSE:To achieve the prevention of measuring errors associated with a temperature change by adjusting an internal resistance of a semiconductor position detector with the control of emission quantity of a light source to eliminate a temperature drift. CONSTITUTION:When an internal resistance decreases with a rise in temperature, a dark current increases and a current flowing through a common electrode 1a increases. But, in the electrode 1a, a voltage drop is caused according to a decrease in the internal resistance. The voltage drop appears as decrease in integration output of an integration circuit 7 to be inputted into a light emitting driver 8 and emission quantity of a light source 2 is adjusted with the control of the voltage drop so that the current flowing through the electrode 1a returns to the original fixed value. In other words, the emission quantity of the light source 2 is reduced and an internal resistance increases in a semiconductor position detector 1 with a decrease in the quantity of light received to stabilize the control when the internal resistance is back to the original state. As a result, the dark current settles down to a fixed value so that the current flowing through the electrode 1a is kept constant. Conversely, when the internal resistance of the element 1 increases with a drop in temperature, the quantity of emission of the light source 2 is adjusted in the direction of increasing thereby keeping the current flowing through the electrode 1a constant.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a position detection device using a semiconductor device detection element (PSD).

<Prior Art> A conventional example of a position detection device using a semiconductor device detection element is one described in Japanese Patent Application Laid-open No. 80503/1983. Its configuration is shown in FIG.

As shown in the figure, in the conventional device, a semiconductor device detection element 21 and a light source 22, such as a light emitting device, are arranged facing each other. Usually, the semiconductor device detection element 21 is attached to a fixed member, and the light source 22 is attached to a movable member that is displaced by a load or the like. light source 22
The emitted light is focused in a pinpoint manner by a lens 23 or a slit provided in front of the light emitted from the semiconductor device detecting element 21, and is irradiated onto the light-receiving surface of the semiconductor device detection element 21.

When the semiconductor device detection element 21 is irradiated with a spot of light on its light-receiving surface with the voltage of the bias power supply 24 applied to its common electrode 21a, the distance from each end electrode to the irradiation spot increases. Inversely proportional amount of current (photocurrent) 11
1t flows. The photocurrents 1+, It extracted from each end electrode of the element 21 are transferred to a current/voltage converter 25.
26 into voltage signals V 1 , , V 2 . These voltage signals v1°■, are introduced into a subtracter 27 to generate a difference signal (V, -V,), and this difference signal is taken out as a position signal of the irradiation spot.

Further, both type pressure signals V + and V t are added together in an adder 28, and this addition output (V + + V t)
is input to the light emitting driver 29 as a control signal, and the amount of light emitted from the light source 22 is controlled by this addition output.

Therefore, even if the light emitting efficiency of the light source 22 fluctuates due to a change in ambient temperature or the like, the amount of light emitted by the light source 22 is controlled to compensate for the fluctuation.

<Problems to be Solved by the Invention> However, in the conventional device described above, the influence of temperature change on the semiconductor device detection element 21 is not sufficiently taken into consideration.

That is, the current taken out from the end electrode of the semiconductor device detection element 21 includes not only a photocurrent but also a dark current, and this dark current increases or decreases with temperature changes.

Now, if α is the increase in each voltage signal V , , V, corresponding to the increase in dark current, the output of each current/voltage converter 25.26 is: ■, 10 α, ■! It becomes ten α.

The increase α due to the dark current is canceled out by subtraction in the subtracter 27, and is no longer included in the position signal.

That is, V + ten α (V 2+ a ) = V + V x
・=-(+) is added to each other in the adder 28, and V, 10 α+Vt+α-V, +Vt+2ff ・-(2
), and the added output includes an increase/decrease due to dark current. Therefore, the amount of light emitted by the light source 22 is controlled not only by the photocurrent of the semiconductor device detection element 21 but also by the dark current. Even if the amount of light received by the element 21 is constant, if the dark current increases or decreases due to temperature changes. In this case, the amount of light emitted from the light source 22 changes. In this case, the amount of light emitted from the light source 22 is controlled to be larger than necessary, which causes a measurement error.

For this reason, the above configuration cannot eliminate the temperature drift of the semiconductor device detection element 21.

The present invention has been made in view of the above problems, and an object of the present invention is to effectively prevent measurement errors caused by temperature changes.

<Means for Solving the Problems> In order to achieve the above-mentioned problems, the present invention provides a position detection device having a semiconductor device detection element and a light source located opposite to the semiconductor device detection element, and which includes a bias power supply. , an input resistor, a voltage detection circuit, and a light emitting driver, the bias power supply is connected to a common electrode of the semiconductor device detection element via the input resistor, and the voltage detection circuit detects voltage fluctuations at the common electrode. The light emitting driver is configured to control the amount of light emitted from the light source based on the detection signal of the voltage detection circuit.

<Function> In the above configuration, when there is a temperature change, the internal resistance of the semiconductor device detection element increases or decreases, and the dark current increases or decreases inversely proportional to this, but the voltage at the common electrode changes in accordance with the increase or decrease in internal resistance. occurs. This voltage fluctuation is detected by a voltage detection circuit, and a detection signal corresponding to the voltage fluctuation is output from the voltage detection circuit.

Since this detection signal is input to the light emission driver, the amount of light emitted by the light source is adjusted to increase or decrease under its control. In a semiconductor device detection element, the internal resistance changes as the amount of light received increases or decreases, and thus the internal resistance is kept constant regardless of temperature changes, and the dark current maintains its original value.

<Example> Hereinafter, the present invention will be described in detail based on an example shown in the drawings.

FIG. 1 is a configuration diagram of a position detection device according to an embodiment of the present invention.

This position detection device includes a semiconductor device detection element, a light source 2 such as a light emitting diode, and a lens 3.

The semiconductor device detection element 1 is usually attached to a fixed member. The light source 2 is a movable member that is displaced by a load or the like, and is mounted at a position facing the semiconductor device detection element 1 through the lens 3.

Further, the position detection device of this embodiment includes a single current/voltage converter 4, a bias power supply 5, an input resistor 6, an integration circuit 7 as a voltage detection circuit, and a light emission driver 8. .

The current/voltage converter 4 converts the photocurrent 1. taken out from one end electrode of the semiconductor device detection element 1. In this embodiment, it is composed of a negative feedback inverting amplifier, and its output V1 is taken out as it is as a position signal. The other end electrode of the semiconductor device detection element 1 is grounded.

The bias power supply 5 connects the common electrode 1 of the semiconductor device detection element 1
It applies a bias voltage to a, and is connected to the common electrode 1a via an input resistor 6.

Here, the integrating circuit 7 is connected to the common electrode 1a as described above.
The circuit operates as a voltage detection circuit that detects voltage fluctuations in the circuit.In this example, it is composed of a differential amplifier 9, an integrating resistor 10, and a capacitor 11, and the non-inverting input terminal of the differential amplifier 9 is connected to the common electrode of the element l. 1a, and the voltage of the bias power supply 5 divided by a pair of voltage dividing resistors 12 and 13 is applied to the inverting input terminal of the differential amplifier 9 via an integrating resistor IO. There is.

The light emission driver 8 inputs the output of the integrating circuit 7 and controls the amount of light emitted from the light source 2 based on this integrated output.

The operation of the above configuration will be explained.

When the element temperature changes, its internal resistance increases or decreases, and the dark current increases in inverse proportion to this, and the total amount of currents r+ and Iz flowing from each end electrode, that is, the current flowing through the common electrode 1a increases or decreases. Become.

Now, if the internal resistance decreases due to temperature rise, the dark current increases and the current flowing through the common electrode +a also increases.
At the common electrode 1a, a voltage drop occurs in accordance with the decrease in internal resistance.

Since such voltage fluctuations are integrated by the integrating circuit 7,
Said voltage drop appears as a decrease in the integrated output. This integrated output is input to the light emitting driver 8, and under its control, the amount of light emitted from the light source 2 is adjusted so that the current flowing through the common electrode 1a returns to its original constant value.

That is, the amount of light emitted from the light source 2 is reduced, and the semiconductor device detection element! In this case, as the amount of light received decreases, the internal resistance increases, and control becomes stable when the internal resistance returns to its original state. Now, the dark current has settled down to a constant value, and the common electrode 1
The current flowing through a is also kept constant.

Conversely, if the internal resistance of the element 1 increases due to a decrease in temperature, the amount of light emitted from the light source 2 is adjusted to increase.
Regardless of the temperature drop, the internal resistance decreases and the common electrode 1
The current flowing through a is kept constant.

On the detection output side of the semiconductor device detection element 1, the current 11 from one end electrode is converted into a voltage signal V, and the voltage signal 1 is taken out as a position signal. In the conventional device, the detection outputs V , , V obtained from both ends of the element, respectively, are
, and treat the difference signal as a position signal. However, as mentioned above, if the total amount of currents r+ and It from both end electrodes of the semiconductor device detection element l is always constant, , detection output V from one end of the semiconductor device detection element 1
By using only + (or ■), this can be treated as a position signal. That is, V, +V, = C (-constant) ・・・・・・・・・・・・
・(3)V, -C-V, ...
...(4) V, =V, -V, -(C-V,)-V.

=C-2V, (5), and one of the detection outputs V, (or Vt) can be treated as a position signal. Of course, as shown in the conventional example in Figure 2, a current/voltage converter is connected to each end electrode, and a subtracter is provided at the subsequent stage to calculate the difference between the outputs of each current/voltage converter. You can also do it like this.

Note that a voltage may be applied to one terminal of the integrating resistor 10 constituting the integrating circuit 7 in the above embodiment from a power source different from the bias power source 5.

Further, as the voltage detection circuit, in addition to the integrating circuit 7 centered on the differential amplifier 9 as in the embodiment, a differential amplifier that introduces the voltage of the common electrode 1a and the reference voltage may be used.

In addition, although a one-dimensional semiconductor device detection element 1 is used in the embodiment, a two-dimensional one can also be used. For example, one more set of current/voltage converters 4) is required.

<Effects of the Invention> As described above, according to the present invention, the internal resistance of the semiconductor device detection element is adjusted to increase or decrease by controlling the amount of light emitted from the light source, so even if there is a temperature change, the dark current does not increase or decrease accordingly. is suppressed, the total amount of current flowing from both end electrodes of the element is kept constant, and temperature drift in measured values can be eliminated.

Furthermore, if the amount of light emitted by the light source is feedback-controlled based on the state of the bias side of the semiconductor device detection element as in the present invention, the detection output side of the element is equipped with a subtracter or a subtractor like the conventional device. There is no need for a pair of current/voltage converters, and it is sufficient to provide a single current/voltage converter, thereby simplifying the circuit configuration.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of a position detection device according to an embodiment of the present invention, and FIG. 2 is a configuration diagram of a conventional device. l...Semiconductor device detection element, 1a...Common electrode, 2
・Light source, 4. Current/voltage converter, 5. Bias power supply, 6. Human resistance, 7. Integrating circuit (voltage detection circuit).

Claims (1)

[Claims] (1) A position detection device having a semiconductor position detection element and a light source located opposite to the semiconductor position detection element, comprising a bias power supply, an input resistor, a voltage detection circuit, and a light emission driver, the bias power supply is connected to the common electrode of the semiconductor position detection element via an input resistor, the voltage detection circuit detects voltage fluctuations at the common electrode, and the light emitting driver detects voltage fluctuations based on the detection signal of the voltage detection circuit. 1. A position detection device that controls the amount of light emitted from a light source.