JPS6344175B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical displacement conversion device that detects a displacement amount corresponding to a physical quantity as an electric signal using light.

<Background> Conventionally, displacement conversion devices for detecting displacement are
For example, by arranging fixed electrodes facing each other on both sides of a movable electrode, and displacing the movable electrode in the direction in which the fixed electrodes are arranged in accordance with the displacement, the capacitance between the movable electrode and the two fixed electrodes can be increased. There is a method that detects displacement by utilizing the differential change in .
In such a displacement conversion device, a movable electrode holding part is stacked on a part holding one fixed electrode, and a part holding the other fixed electrode is stacked on top of each other. On the other hand, it was necessary to create a structure that was completely symmetrical left and right. Creating such a structure requires high precision machining and assembly precision, and even if there is a slight deviation, the error will gradually increase due to the nature of the stacked structure, so it is necessary to pay sufficient attention to the structure production. However, it had become expensive.

<Summary of the Invention> An object of the present invention is to provide an optical displacement transducer that has a relatively simple structure and can therefore be manufactured at low cost.

According to this invention, the light emitting part and the light receiving part are arranged so that the light from the light emitting part is received by the light receiving part,
A light-shielding plate that is displaced according to a physical quantity is arranged between the light-emitting part and the light-receiving part, and the amount of light received by the light-receiving part is changed according to the displacement of this light-shielding plate, so that the electrical signal output from the light-receiving part is This corresponds to the displacement of the light shielding plate. As this light-shielding plate, one whose light transmission amount changes depending on an electric signal is used, and the electric signal applied to the light-shielding plate is periodically changed. The output of the light receiving section is taken out in synchronization with this periodic change,
Based on this output, the light emitting section is controlled so that the electrical signal from the light receiving section remains approximately constant while the amount of light transmitted through the light shielding plate is greatly controlled. In this way, even if the characteristics of the light emitting section, the light receiving section, and even the conversion section to which the output of the light receiving section is supplied vary due to temperature fluctuations, the amount of displacement can be detected correctly without being affected by this.

<First Embodiment> FIG. 1 shows an embodiment of the optical converter according to the present invention, which includes a light emitting section 11 such as a light emitting diode and a light receiving section that receives light from the light emitting section 11 and converts it into an electrical signal. 12 are provided. These light emitting parts 11
A light shielding plate 13 is arranged between the light receiving section 12 and the light receiving section 12 . The light shielding plate 13 has a plate surface perpendicular to the arrangement direction of the light emitting section 11 and the light receiving section 12, and is displaced parallel to the plate surface according to the physical quantity to be detected. The amount of light received changes.
The output of the light receiving section 12 is amplified by an amplifier 14 and used as a detection output.

In this invention, the light shielding plate 13 is one whose light transmission amount can be controlled by an electric signal, and the light transmission amount of the light shielding plate 13 is periodically controlled. For example, a liquid crystal shutter is used as the light shielding plate 13,
A switch 1 is connected between both electrodes of the liquid crystal shutter 13.
By repeatedly turning on and off 5, the voltage _E3 of the power source 16 can be applied or removed. For example, when the voltage _E3 is applied to the liquid crystal shutter 13, the liquid crystal shutter 13 is closed, that is, becomes opaque, and when the switch 15 is turned off, it becomes transparent, ideally the same state as when the light shielding plate 13 is removed.

The output of the light receiving section 12 when the amount of light transmitted through the light shielding plate 13 is large is extracted. That is, the output of the amplifier 14 is selectively supplied to the smoothing circuits 18 and 19 by the switch 17. Switch 17 and switch 15 are synchronously controlled by the output of oscillation circuit 21, and when voltage is applied to liquid crystal shutter 13, switch 1
7 is supplied to the smoothing circuit 18. The output of the smoothing circuit 18 is outputted to the output terminal 22 as a detection signal corresponding to the displacement of the light shielding plate 13.

The light emitting section 11 is controlled so that the output of the smoothing circuit 19 becomes a constant value. For example, the output of the smoothing circuit 19 is supplied to the inverting input side of the operational amplifier 23, and the reference voltage _E2 is applied from the power supply 24 to the non-inverting input side of the operational amplifier 23. The voltage E ₁ of the power source 25 of the light emitting section 11 is controlled according to the difference between both inputs of the operational amplifier 23 . The output of the power source 25 is applied to the light emitting section 11 via a resistor 26 as required.

Now, the light shielding plate 13 is in an opaque state, and when the displacement x=0, half of the maximum amount of light received by the light receiving section 12 is received, and the maximum displacement is ±a. If the width of the light receiving section 12 is L, the light-to-electrical conversion efficiency of the light receiving section 12 is k, and the amount of light emitted from the light emitting section 11 is Q, then the output of the smoothing circuit 18 is
Since V ₁ is proportional to the output of the amplifier 14 when the light shielding plate 13 is in an opaque state, V ₁ =kQL(a±x) (1). The output V ₂ of the smoothing circuit 19 is transmitted to the light shielding plate 13
Since it is proportional to the output of the amplifier 14 in the transparent state, it can be expressed as V ₂ =kQL×2a (2). Since the voltage _E1 of the power supply 25 is controlled so that this _V2 is equal to the reference voltage _E2 , kQ= _E2 /L×2a _V1 = _LE2 /L×2a(a±x)=E ₂ /2a(a±x) (3) In this way, the output V ₁ of the terminal 22 is proportional to the displacement x of the light shielding plate 13 and is independent of the light amount Q of the light emitting section 11 and the conversion efficiency k of the light receiving section 12. Therefore, even if the light quantity Q and efficiency k change due to ambient temperature changes, aging, etc., the detection output will be affected by this change.
V ₁ is not affected.

<Second Embodiment> FIG. 2 shows a second embodiment of the present invention, in which parts corresponding to those in FIG. 1 are given the same reference numerals. In this example, the power supply 16 is omitted, and instead a resistor 27 is connected in parallel with the resistor 26 via the switch 15. Further, a resistor 28 is inserted in series with the light emitting section 11, and both ends of the resistor 28 are connected to both electrodes of the liquid crystal shutter 13 as a light shielding plate through a threshold element 29 such as a Zener diode.
When the switch 15 is off, the current flowing through the light emitting section 11 is
i ₁ , and depending on the voltage across the resistor 28 at this time, the threshold element 29 is non-conductive and the liquid crystal shutter 1
3 is transparent, but when the switch 15 is on, a current _i2 flows through the light emitting part 11, and the voltage across the resistor 28 based on this current _i2 makes the threshold element 29 conductive, and the liquid crystal shutter is turned on. the threshold value of threshold element 29 such that a voltage is applied to 13 to make it opaque;
The resistance values of the resistors 26, 27, and 28 are selected.

When i ₁ :i ₂ = 1:n, the light amount Q ₁ of the light emitting unit 11 based on i ₁ and the light amount Q ₂ based on i ₂ are also Q ₁ :Q ₂ =
1:n. As before, V ₁ = kQL (a±x), V ₂ = kQ ₁ L×2a kQ ₁ = E ₂ /L×2a=KQ ₂ /n∴V ₁ = nE ₂ /2a (a±x). , the detection output V ₁ is proportional to the displacement x, and k,
It is not affected by fluctuations such as Q ₁ and Q ₂ .

<Third Embodiment> FIG. 3 shows a third embodiment of the present invention. In this example, the amplifier 23 compares the output V ₂ of the smoothing circuit 19 and the reference voltage E ₂ when the light transmittance of the light shielding plate 13 is high, and the comparison output and the light transmittance of the light shielding plate 13 are The operational amplifier 31 calculates the difference between the output V ₁ of the smoothing circuit 18 when the displacement is small, that is, the output proportional to the displacement x.
The power source 25 of the light emitting section is controlled by the output of the operational amplifier 31, and both inputs of the operational amplifier 23 are connected.
Both inputs of the operational amplifier 31 are made to match each other. Operational amplifier 23 as a detection output of displacement x
The output is taken out to the terminal 22. As in the previous case, V ₁ = kQL (a±x), V ₂ = kQL×2a, and E ₂ = V ₂ , and the output voltage V ₀ of the terminal 22 is V ₁ It works so that it becomes. Therefore, V ₀ =V ₁ =kQL(a±x)=E ₂ /2a(a±x), and the output V ₀ of the terminal 22 is proportional to the displacement x. In this embodiment, the output terminal 22
Since the output _V0 is fed back, it is less susceptible to external noise. That is, in the embodiment shown in FIGS. 1 and 2, when noise enters the signal path from the smoothing circuit 18 to the output terminal 22, it is output to the output terminal 22. However, in the embodiment of FIG. 3, such noise is suppressed because the entire signal is fed back.

<Other Embodiments> In the embodiment shown in FIG. 3, the output V ₁ of the smoothing circuit 18 may be amplified by the amplifier 32 and supplied to the comparison amplifier 31 as shown in FIG. Or conversely, the output V ₀ of the output terminal 22 is divided and the comparison amplifier 3
It may be supplied to 1.

In the previous example, the light shielding plate 13 was made to become transparent when no voltage was applied, but it may be difficult to make it completely transparent. In such a case, for example, as shown in FIG.
The light reaching the liquid crystal shutter 13 is made sure to pass through the liquid crystal shutter 13, and one half of the liquid crystal shutter in the displacement direction has no electrodes and is always transparent, a transparent part 13a, and the other half has an electrode formed thereon. It is assumed that the variable part 13b has transparency controlled. In this way, even if the light transmittance of the liquid crystal shutter changes due to temperature or aging, no error will occur in the output _V0 . In the above description, the light shielding plate 13 is made of a material that has low light transmittance and becomes opaque when a voltage is applied, but a liquid crystal shutter that has high light transparency when a voltage is applied may also be used. In that case, for example, the 6th
As shown in the figure, one half in the displacement direction of the liquid crystal shutter and the other half are separated and provided with opposing electrodes, and a voltage is constantly applied to one half from the power supply 16 to form a transparent part 13a, and the other half Part is switch 1
5, the voltage may be applied on and off to form the variable portion 13b. In the embodiment shown in FIG. 2, instead of switching the resistors 26, 27, the voltage E ₁ of the power supply 25 is
may be switched at a constant ratio, and a current source may be used as the power source 25. The light emitting section 11 may be an incandescent lamp.

<Effects> As described above, according to the optical displacement transducer of the present invention, as can be understood from its configuration, it does not have to be constructed by stacking each part one after another as in the case of a capacitance type. It can be made easily. Moreover, even if the constants and characteristics of the entire system including the light emitting section, the light receiving section, and other amplifying sections in the embodiment shown in FIG. 3 change, the output is not affected by this.

[Brief explanation of the drawing]

1 to 3 are block diagrams showing an example of an optical displacement converter according to the present invention, FIG. 4 is a block diagram showing a partial modification thereof, and FIGS.
Each figure shows a modified example of the light shielding plate 13. 11: light emitting section, 12: light receiving section, 13: light shielding plate,
18, 19: Smoothing circuit, 21: Oscillation circuit, 22:
Output terminal, 23, 31: comparison amplifier, 24: reference power supply.

Claims (1)

[Claims] 1. A light-emitting part that generates light, a light-receiving part that receives light from the light-emitting part, and a light-receiving part that is disposed between these light-emitting parts and light-receiving parts, and that is displaced according to a physical quantity, and that the light-receiving part changes according to the displacement. A light-shielding plate capable of changing the amount of incident light and the amount of light transmitted by an electric signal, a means for periodically changing the electric signal applied to the light-shielding plate, and a means for periodically changing the electric signal applied to the light-shielding plate; means for synchronously extracting signals from the light receiving section; and controlling the light emitting section so that the electrical signal from the light receiving section is substantially constant while the amount of light transmitted through the light shielding plate is greatly controlled. An optical displacement transducer comprising means for.