JPH01141315A - Displacement detecting device - Google Patents

Abstract

PURPOSE:To obtain the device which can detect a movement of an object in a remote place by radiating a laser light to an object through a coupling optical system and recoupling its reflected light to the original semiconductor laser to utilize a self-coupling effect of a semiconductor laser. CONSTITUTION:On an object whose displacement is to be detected, a displacement part (slit plate) 5 having a surface pattern formed by a difference of a reflection factor is provided. With respect to this displacement part 5, a laser light emitted from a semiconductor laser 1 is transmitted by an optical fiber 3 and radiated, and also, its reflected light is made reincident on the original semiconductor laser 1 through the same optical fiber 3. Subsequently, by a characteristic variation detecting means (photodetector) 2, a variation of an operation characteristic of the semiconductor laser 1 caused by a variation of the return light quantity due to a displacement of the displacement part 5 is detected, and based on its result, a displacement of the displacement part 5 is detected.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention projects the output of a semiconductor laser onto a target at a remote location via a coupling optical system, and recombines the reflected light to the semiconductor laser. The present invention relates to a displacement detection device for detecting movement, etc. of

BACKGROUND OF THE INVENTION There is a well-established technology for remotely detecting displacement that utilizes various electrical detectors and electrical signal transmission means.

For example, in a capacitive displacement detector, a change in capacitance between electrodes in a gap to be measured is detected, and the change is converted into the intensity of an electric signal.

To remotely transmit electrical signals from a displacement detector, it is necessary to provide a transmission amplifier circuit on the detector side and supply power from outside.

Furthermore, there are optical encoders that use light to detect displacement, but since both the light-emitting element and the light-receiving element are located within the detector, remote signal transmission is performed exclusively by electrical means.

(Problems to be Solved by the Invention) A remote displacement detector that utilizes such electric wires and employs remote transmission technology using electric signals has the following inherent problems.

■ In environments where explosion-proof properties are required, measures such as complete sealing must be added as an explosion-proof measure.

■ In long-distance remote detection, power loss occurs due to electric wires, and in signal transmission, there is a problem in that electromagnetic interference noise is added to the minute signal.

It is also vulnerable to electromagnetic interference caused by lightning strikes.

■ Electric wire is inferior in weight and heat resistance compared to optical fiber.

In order to solve the problems of these electrical remote detectors,
Various detectors using optical fibers as transmission lines have been proposed, but at present there are problems such as the influence of disturbances on the transmission line fibers and the large number and types of optical elements used.

As an example of signal detection using a semiconductor laser, there is a method named SCOOP that utilizes its self-coupling effect (Applied Physics Vol. 51).

No. 4 (1982, pp. 450-453) In this scoop method, recording and reading from an optical disk located close to the semiconductor laser is performed by utilizing the self-coupling effect of the semiconductor laser.

At this time, since the semiconductor laser is fixed at a position several tens of millimeters from the optical disk surface, remote detection is difficult, and the detection target is limited to the presence or absence of optical disk recording pits.

An object of the present invention is to irradiate a target with laser light through a coupling optical system and combine the reflected light with the original semiconductor laser, thereby preventing changes in operating characteristics due to the self-coupling effect of the semiconductor laser. An object of the present invention is to provide a displacement detection device that detects displacement of an object.

(Means for Solving the Problems) In order to achieve the above object, a displacement detection device according to the present invention includes a semiconductor laser, a displacement portion having a surface pattern formed by a difference in reflectance, and a displacement detection device of the semiconductor laser. A coupling optical system that focuses the emitted light on the surface of the displaced portion and re-enters the reflected light from the focused point into the semiconductor laser, and a change in the amount of returned light due to displacement of the displaced portion in a direction perpendicular to the incident direction. The semiconductor laser includes characteristic change detection means for detecting changes in the operating characteristics of the semiconductor laser.

According to the present invention, an optical fiber is used to connect the displacement part, which is the part to be detected, and the semiconductor laser, and the two optical fibers share the light transmission and light receiving paths, and the displacement of the detection part is converted into an on-off change in light intensity. By converting, it is possible to provide a displacement detection device that reduces the influence of disturbances and the like, and detects displacement by detecting a change in characteristics due to a self-coupling effect due to the return light of a semiconductor laser, which is a light emitting element.

The slit plate forming the displacement part, which is one of the functional parts for converting a displacement signal into a light intensity signal, has its reflecting surface fixed at a position where the beam diameter of the detection light is the minimum, and has a notch fulcrum. Due to the mechanism, the displacement side has low rigidity, and the other orthogonal 2
High rigidity can be achieved for the shaft.

The emitted light from the semiconductor laser propagates through the optical fiber, and the presence or absence of the reflective film on the slit plate determines the presence or absence of return light, propagates through the same optical fiber again, and returns to the semiconductor laser. This return light enters the interior from the semiconductor laser emitting end,
Semiconductor lasers produce self-coupling effects, and the emission intensity generally increases.

At this time, what influences the self-coupling effect is the returned light whose polarization plane components match the output light polarization plane, and in particular, the influence of the phase can be ignored, allowing a configuration that depends on the intensity of the returned light.

The optical fiber that connects the semiconductor laser and the slit plate can be extended to a length of several kilometers by providing a polarization maintaining function.

The displacement to be detected is expanded or contracted by the coupling mechanism using the notch fulcrum as the fulcrum, and the slit plate integrated with the movable part of the coupling mechanism is displaced within a determined plane perpendicular to the incident light. .

(Example) The present invention will be described in more detail below with reference to the drawings and the like.

FIG. 1 is a schematic diagram showing a first embodiment of a displacement detection device according to the invention.

The semiconductor laser 1 is provided so as to generate backward light in the opposite direction to the forward light of the chip.

The forward light is guided toward a coupling optical system composed of an optical fiber 3 and a condensing element 4. The rear light is made incident on the light receiving element 2 and detected.

Laser light is input into the optical fiber 3, propagated therein, and emitted from the other end, and is focused by the focusing element 4.

The surface of the displacement part is placed at a position where the diameter of the condensed beam is minimized.

The displacement part is formed by a reflective slit plate 5 having an encoder function, and the slit plate 5 is displaced in the vertical direction in the figure due to the displacement input to be detected, but the reflective surface of the slit plate 5 is always in the same plane. It is supported as such.

The reflective surface of the slit plate 5 is provided with slit-shaped reflective surfaces and transparent surfaces alternately.

When the reflective surface corresponds to the convergence point of the laser beam, the reflected laser beam returns along the same optical path as the outgoing path and passes through the semiconductor laser l.
Return to the light emitting point.

When the convergence point of the laser beam is on the transmission surface, the propagating light is transmitted to the rear of the slit plate 5, and there is no returning light as described above.

FIG. 2 shows the emission intensity characteristics of the semiconductor laser 1 with and without a return destination for the injected current.

It is shown that the emission intensity changes by ΔL between the case where there is return light and the case where there is no return light for a certain injection current is that is emitting laser light.

An antireflection film is added to the output end face of the semiconductor laser 1 shown in FIG. 1 in the direction toward the optical fiber 3 to prevent reflection of the returning light and to further increase the change in emission intensity ΔL.

In the embodiment shown in FIG. 1, the intensity of the emitted light increases when there is return light, so by detecting this with the light receiving element 2, it is possible to determine whether or not there is a reflective surface at the focal point. Can be done.

If a reflective surface other than the reflective surface of the slit plate 5 is present between the optical path of the light emitted from the semiconductor laser l, reflected by the reflective surface of the slit 5, and returned to the semiconductor laser l, a loss of transmitted light will occur.

As a result, even if there is no reflective surface at the focal point, return light is generated, and when there is a reflective surface, the reflected light is reduced.

The luminous intensity when there is no reflective surface increases due to reflective surfaces other than the reflective surface of the slit plate 5, and the luminous intensity when there is a reflective surface is smaller than in the ideal case (when there is no other reflection). Become.

Therefore, ΔL in FIG. 2 is reduced.

Therefore, in this embodiment, in order to reduce harmful reflections in the optical path as much as possible, antireflection measures such as adding an antireflection film to the end face of each optical element are taken.

Furthermore, the change in emission intensity due to the presence or absence of the returned light in FIG. 2 is caused by the returned light whose polarization plane components match the polarization plane of the output light. Therefore, in FIG. 1, elements that disturb the plane of polarization in the optical path are removed so that the plane of polarization is maintained until the emitted light from the semiconductor laser 1 returns to the semiconductor laser 1 as return light.

The optical fiber 3 used has a function of maintaining the plane of polarization.

FIG. 3 is a schematic diagram showing the main part configuration of a second embodiment of the displacement detection device according to the present invention. Note that in this figure, the first
The condensing element 4 and the slit plate 5, which are common components with the embodiment described above, are omitted.

In this embodiment, the characteristic change detection means of the semiconductor laser 1 is replaced with the light receiving element 2 shown in FIG. 1, and a means for electrically detecting the resistance change between the terminals of the semiconductor laser 1 is used.

This is an example of a configuration in which a detection output signal is obtained from a connection point between a semiconductor laser 1 and a drive power source.

A power supply 7 supplies the semiconductor laser 1 with enough current to emit laser light.

Emitted light from the semiconductor laser 1 is made incident on an optical fiber 3 that constitutes a coupling optical system.

The returned light returns to the semiconductor laser 1 again using a configuration similar to that described in connection with FIG.

At the connection point between the power supply 7 and the semiconductor laser 1, the voltage between the terminals of the semiconductor laser 1 is detected, amplified by the amplifier 6, and taken out as a detection signal.

FIG. 4 is a graph showing the change (ΔV) in the voltage across the terminals of the semiconductor laser diode l with respect to the injection current i when there is return light and self-coupling occurs in the semiconductor laser.

This graph shows that due to the self-coupling effect due to the return light, the voltage between the terminals of the semiconductor laser is the threshold value (i th) at the injection current i.
This shows that there is a large change in Δ■ when it is in the vicinity.

Therefore, in this embodiment, the semiconductor laser 1 is driven near this threshold current (i th).

This change (ΔV) is detected by the amplifier 6, and the existence of the displacement can be confirmed by the presence or absence of the returned light.

FIG. 5 is a block diagram showing an embodiment of a displacement detection device having an absolute encoder function and detecting the displacement of a displacement section as an absolute position.

In this device, the displacement section for converting displacement into an optical signal has an absolute encoder function.

A slit row at a certain position of the absolute encoder slit plate 12 corresponds to that position as a sign of the presence or absence of a reflective surface.

In this embodiment, the absolute encoder slit plate 12 is formed of an n-byte slit array.

A semiconductor laser, a coupling optical system, and means for detecting a change in characteristics of the semiconductor laser are prepared for each of the bites.

A semiconductor laser 1- to which an operating current is supplied from a power supply 7.
Light receiving elements 2-1 to 2-n, which are means for detecting characteristic changes of the respective semiconductor lasers, are provided for the respective semiconductor lasers 1 to 1-l-n.

For each semiconductor laser 1-1 to 1-n, fiber coupling optical elements 9-1 to 9-n, and optical fibers 3-1 to
3-n are made to correspond to each other, and the terminals of each optical fiber 3-1 to 3-n are made to correspond to each byte by a condensing element array 10 composed of condensing elements 1O-1-10-n. .

FIG. 6 is a perspective view showing the relative positions of the absolute encoder slit-type displacement section used in the embodiment, the displacement transmission mechanism that supports it, and the condensing element array.

Each beam focused by each element of the condensing element array 10 is projected onto the absolute encoder slit plate 12 at its minimum beam diameter position.

The absolute encoder slit [12 is supported by a displacement transmission mechanism 13.

The absolute encoder slit plate 12 is incorporated into a displacement transmission mechanism 13 having four notched support points 13h.

The lower side of the displacement transmission mechanism 13 is fixed as a fixed part, and the upper side thereof becomes a movable part. When a displacement input shown by an arrow is applied to the upper side, the absolute encoder slit plate 12 supported by the displacement transmission mechanism 13 is moved in parallel. It will be done.

The notch fulcrum portion 13h is thin and freely bends as a kind of connection point, so it can move freely in the direction of the displacement input axis, but it has high rigidity in the direction of the orthogonal axis, and is not affected by external forces such as vibrations. No displacement.

Therefore, the absolute encoder slit plate 12 can always be held at the minimum diameter position of the beam condensed by the condensing element array 10.

FIG. 7 is a plan view showing another embodiment of the absolute encoder slit plate and the displacement transmission mechanism, and FIG.
The one shown in the figure is used for enlarging the displacement input, and the one shown in the same figure (B) is used for reducing the displacement input.

In each figure, absolute encoder slit plate 1
2 is supported by a displacement transmission mechanism 13, and 13h indicates a notched fulcrum portion.

The one shown in FIG. 7(A) has a displacement input of 12/l.

The one shown in the same figure (B) has a displacement input of 12 /
l Reduce to 1.

FIG. 8 is a plan view showing an example of displacement input.

The absolute encoder slit plate 12 and the displacement transmission mechanism 13 are substantially the same as those shown in FIG. 7(A).

The displacement of the air 1114 is magnified and transmitted to the absolute encoder slit plate 12.

FIG. 9 is a block diagram showing still another embodiment of the displacement detection device according to the present invention.

Similar to the embodiment shown in FIG. 5, this embodiment is an embodiment in which displacement is detected as an absolute position.

A single semiconductor laser 1 is used and a coupling optical system different from that of the previous embodiment is used.

The coupling optical system includes a fiber coupling optical element 9. - Main optical fiber 3, demultiplexer (combiner) 11. It is composed of a delay element group 18 and a condensing array 10.

Light from the semiconductor laser 1 is made to enter one optical fiber 3 by an optical fiber coupling optical element 9.

The output of the optical fiber 3 is demultiplexed according to the number of bytes of the absolute encoder slit plate 12 (
It is demultiplexed by a multiplexer 11.

It is connected to the corresponding light collecting element of the light collecting array 10 through a delay element group 18 that delays each output of this demultiplexer 11 by a different time, and is connected to a corresponding part of the absolute encoder slit plate 12 which is a displacement part from each one. irradiate.

As this displacement portion, all of the absolute encoder slit plates 12 described above with reference to FIGS. 6, 7, and 8 can be used.

The slit plate 12 has an n-byte slit row, and the presence or absence of a reflective surface is represented by a code corresponding to its position.

The light reflected by the reflective surface follows a path opposite to that described above, returns to the semiconductor laser 1, and is coupled as light.

Delay lines 18-1, 18-2, etc. that constitute the delay element group 18
Assuming that the delay times of #18-n are short in this order, the reflected light from the absolute encoder slit plate 12 is #1.
, 62 to #n and combined.

FIG. 10 is a waveform diagram for explaining the operation of this embodiment.

The semiconductor laser 1 is operated with a constant injection current as shown in FIG. 10(A).

As shown in the same figure (C), the reflection pattern on the surface of the absolute encoder slit plate 12 is (#
1. #2. #3...n) in the order of (1, 1, 0...
・0, ■).

Note that 1 is a reflective surface, and O means transmission.

The light receiving element 3 exhibits a luminescence pattern over time as shown in FIG. 10(B).

This light emission pattern allows displacement to be detected as an absolute position.

(Effects of the Invention) As explained above, the displacement detecting device according to the present invention includes a semiconductor laser, a displacement portion having a surface pattern formed by a difference in reflectance, and transmitting light emitted from the semiconductor laser through an optical fiber. a coupling optical system that focuses the light on the surface of the displacement part and re-enters the reflected light from the focal point into the semiconductor laser; It consists of characteristic change detection means for detecting changes in the operating characteristics of the semiconductor laser.

According to this configuration, compared to conventional remote displacement detection devices consisting of various electrical detectors and electrical signal transmission means,
The simple configuration provides (1) explosion-proof properties, (2) long-distance transmission (
3) It is possible to provide a device that solves problems such as noise resistance characteristics.

Therefore, the device according to the present invention is widely applicable to the field of industrial measurement and aircraft-mounted equipment.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing an embodiment of a displacement detection device according to the invention. FIG. 2 is a graph showing the emission intensity corresponding to the injected light of the semiconductor laser. FIG. 3 is a schematic diagram showing the main parts of another embodiment of the displacement detection device according to the present invention. FIG. 4 is a graph for explaining the operation of the displacement detection device shown in FIG. 3. FIG. 5 is a block diagram showing still another embodiment of the displacement detection device according to the present invention. FIG. 6 is a perspective view showing the relationship between the condensing array and the absolute encoder of the displacement detecting device shown in FIG. 5. FIG. FIG. 7 is a plan view showing an example of a variable magnification mechanism of an absolute encoder. FIG. 8 is a schematic diagram showing an example of displacement input. FIG. 9 is a block diagram showing still another embodiment of the displacement detection device according to the present invention. FIG. 10 is a waveform diagram for explaining the operation of the embodiment shown in FIG. 9. l... Semiconductor laser 2... Light receiving element 3... Optical fiber 4... Focusing element 5... Displacement part (slit plate) 6... Amplifier 7... Power supply 9... Fiber Coupling optical element 10...Condenser array 11...Demultiplexer (combiner) 12...Displacement part (absolute encoder slit plate) 13...Displacement transmission mechanism 13h...Notch fulcrum 1
4...Pressure-displacement converter (space) 16...Demultiplexer/combiner 18...Delay element group

Claims (11)

[Claims] (1) A semiconductor laser, a displaced portion having a surface pattern formed by a difference in reflectance, and the emitted light of the semiconductor laser is transmitted through an optical fiber to be focused on the surface of the displaced portion and from the focal point. a coupling optical system for re-entering the reflected light into the semiconductor laser, and a characteristic change detection means for detecting a change in the operating characteristics of the semiconductor laser due to a change in the amount of returned light due to displacement of the displacement part in a direction perpendicular to the direction of incidence. displacement detection device. (2) The displacement detection device according to claim 1, wherein the displacement section is a reflective slit plate having an encoder function. (3) The semiconductor laser is provided such that its chip generates backward light in the opposite direction to the forward light in the direction of the coupling optical system, and the characteristic change detection means detects the light emission characteristic by detecting the backward light. 2. The displacement detection device according to claim 1, which is a light receiving element that detects a change in . (4) The displacement detecting device according to claim 1, wherein the characteristic change detecting means is a means for electrically detecting a change in resistance between terminals of the semiconductor laser. (5) A patent claim in which the coupling optical system uses an optical fiber having a function of maintaining the polarization plane of propagating light, so that the polarization plane of the light emitted from the semiconductor laser is maintained together in the reciprocating optical path in the optical fiber. The displacement detection device according to item 1. (6) The displacement detection device according to claim 1, wherein the optical element terminal surface in the optical path formed by the condensing element or the optical fiber of the coupling optical system is formed with an antireflection film or an antireflection shape. . (7) The semiconductor laser has an anti-reflection film added to the end face in the direction toward the optical fiber among the emission end faces of the semiconductor laser chip, thereby increasing the change in semiconductor laser characteristics. Displacement detection device described. (8) The displacement part has a surface pattern formed by a difference in reflectance and has an absolute encoder function,
The semiconductor lasers are arranged in a number corresponding to each byte of the displacement section, and the optical coupling optical system optically couples each of the semiconductor lasers and a corresponding portion of the displacement section to combine the emitted light of each semiconductor laser. is transmitted through an optical fiber and focused on the corresponding surface of the displaced portion, and the reflected light from the focused point is re-injected into each of the semiconductor lasers, and the characteristic change detection means is configured to detect a change in characteristics perpendicular to the direction of incidence of the displaced portion. 2. The displacement detection device according to claim 1, which detects a change in the operating characteristics of each of the semiconductor lasers due to a change in the amount of returned light due to a directional displacement. (9) The displacement part has a surface pattern formed by a difference in reflectance and has an absolute encoder function,
The coupling optical system includes an optical fiber into which light from the semiconductor laser is input, a demultiplexer that demultiplexes the output of the optical fiber in accordance with the number of bytes of the absolute encoder;
a delay element group for delaying each output of the demultiplexer by a different time; the output of the delay element group is focused and irradiated onto the surface of the displacement portion, and the reflected light from the surface is received; the characteristic change detection means , the displacement according to claim 1, which is a characteristic change detection means for detecting a change in operating characteristics of the semiconductor laser over time due to a change in the amount of returned light due to a displacement of the displacement part in a direction perpendicular to the incident direction. Detection device. (10) The displacement unit having the absolute encoder function is integrally formed with a displacement transmission mechanism having one side fixed via a plurality of circular arc notch fulcrums, and is moved by expanding or contracting a displacement input. Displacement detection device according to range 8 or 9. (11) The displacement detection device according to claim 8 or 9, wherein the displacement input is inputted to the displacement transmission mechanism by a pressure displacement conversion section using pressure as displacement.