JPH0424519A - Displacement detecting apparatus - Google Patents

Abstract

PURPOSE:To make it possible to perform the highly accurate measurement of displace ment independent of the characteristics of light such as wavelengths and the amount of light by emitting laser light on a body to be measured through a reflecting body which is driven by electric pulses, and detecting the displacement based on the changed value of the numbers of pulses before and after the movement of the body to be measured. CONSTITUTION:The position of a body to be measured at the time the number of pulses, when the reflected light is incident on a light detecting sensor 12, becomes N1 is made to be the position of Fa. Then, the expression of relation tan theta1 = b/a holds true. Meanwhile, when the body to be measured is moved to the position of Fb by a distance X, tan theta2 = (b + X)/a is obtained. The number of pulses at the position of Fb from the start of the light detection is made to be N2. Then, the amount of displacement becomes X = a(tan theta2 - tan theta1). Then the number of pulses corre sponding to one rotation of a rotary shaft 14a of a pulse motor is made to be No. Then, theta1 = 2pi X (N1/No) [radian] and theta2 = 2pi X (N2/No) [radian] are obtained. The amount of the displacement X is given as the functions of the pulse numbers N1 and N2. Since the displacement is detected based on the pulse numbers N1 and N2 in this way, the displacement can be detected without the effects of temperature, light density and the like.

Description

[Detailed Description of the Invention] [Purpose of the Invention [Industrial Application Field] The present invention irradiates a measured object with a laser beam and uses reflected light from the measured object to measure the amount of movement of the measured object. The present invention relates to a displacement detection device for detecting displacement.

[Conventional technology]

Conventionally, as a displacement detection device using laser light, a device using a Michelson interferometer has been considered.

As shown in FIG. 5, in this device, light emitted from a light source 1 is split into two by a beam splitter 2, one of which passes through and is guided to a movable mirror 3, and the other is reflected and sent to a fixed mirror. Leads to 4. The beams are reflected by the movable mirror 3 and the fixed mirror 4 and enter the beam splitter 2 again, where they interfere with each other to produce interference fringes. This interference fringe is the movable mirror 3
It changes by moving in the direction of the arrow shown. Therefore, by forming the above-mentioned interference fringes on the light receiving surface of the detector 5, detecting the change in the interference fringes due to the movement of the movable mirror 3, and capturing and integrating them with a counter, the interference fringes are moved based on the wavelength λ of the light. Can measure distance.

Displacement detection devices that utilize changes in the optical path due to movement of the object to be measured have also been considered.

As shown in FIG. 6, in this device, a laser beam from a laser light emitting diode 6 passes through an optical path indicated by a solid line in the figure, is reflected at the surface F1 of the object to be measured, and passes through a light receiving lens 7 to a position detection sensor 8. is incident on one point on the light receiving surface. Furthermore, when the object to be measured is moved until its surface reaches F2, the laser light from the laser light emitting diode 6 passes through the optical path shown by the two-dot broken line in the figure and reaches a predetermined position on the light receiving surface of the position detection sensor 8. incident. At this time, the incident position of the reflected light on the position detection sensor 8 differs before and after the movement. Therefore, by detecting the amount of change in the position detection sensor 8, the amount of movement of the object to be measured is detected.

However, in the displacement detection device using the above Michelson interferometer, the length measurement result is a function of the wavelength λ of the light, so if the wavelength λ changes due to a change in the temperature of the optical path medium, for example, that change will directly result in a measurement error. This appears in the measured value.

Furthermore, in the conventional example shown in FIG. 6, the position detection sensor 8 has temperature dependence and light intensity dependence.

As the amount of light changes, the error increases.

[Problem to be solved by the invention]

Therefore, since the measurement accuracy of conventional displacement detection devices depends on the characteristics of light such as wavelength and light intensity,
There was a problem in that the light itself had to be extremely stabilized, making it difficult to measure displacement with high precision.

The present invention has been made in view of the above-mentioned circumstances, and provides a displacement detection device that enables displacement detection using parameters that do not depend on the characteristics of light, and that easily enables measurement with extremely high precision and a wide range. The purpose is to provide.

[Structure of the Invention [Means for Solving the Problems] In order to solve the above problems, the present invention includes a light source that generates a laser beam, and a light source that is driven by an electric pulse and receives the laser beam from the light source. A reflector for irradiating a fixed object, a light receiving means for receiving reflected light from the object to be measured, and a number of pulses given to the reflector during a period from generating the laser beam to receiving the reflected light. is detected at each position before and after the movement of the object to be measured, and means for detecting the amount of movement of the object to be measured based on the change value of the detected number of pulses.

[For production]

By taking the above measures, the present invention irradiates the object to be measured with laser light from a light source via a reflector driven by an electrical pulse.

The reflected light from the object to be measured is received by a light receiving means, and the number of pulses applied to the reflector is counted from the time when the laser beam is generated until the time when the reflected light is received. Then, after the object to be measured is moved, the number of pulses is counted again in the same manner, and the amount of movement of the object to be measured is determined from the change in the number of pulses before and after the object to be measured is moved.

Therefore, depending on the number of pulses that does not depend on the characteristics of light,
Displacement detection will be performed.

〔Example〕

Examples of the present invention will be described below.

FIG. 1 is a diagram showing a schematic configuration of a displacement detection device according to an embodiment of the present invention. Reference numeral 10 shown in the figure is a light projectile which is pulse-driven using a semiconductor laser as a light source.The laser light emitted from this light projector 10 is reflected by the object to be measured Fa and then enters a condenser lens 11. Ru. A photodetection sensor 12 made of either a phototransistor or a photodiode is installed at the condensing position of the condensing lens 11. The calculation unit 13 has a function of detecting the amount of movement of the object to be measured based on the pulse data sent from the light projector 10 and the photodetection signal sent from the photodetection sensor 12.

The light projectile 10 is connected to a pulse motor 1 as shown in FIG.
4, a pulse motor drive circuit 15 that generates a constant pulse to drive the pulse motor 14, outputs it to the pulse motor 14, and outputs the number of pulses applied to the pulse motor 14 to the calculation unit 13; A rotating body 1 attached to a rotating shaft 14a and provided with a plurality of reflecting mirrors 16a to 16c at different angles on the side surface thereof.
7, and a semiconductor laser light source 18 that makes laser light incident on the rotating body 17. Note that the rotating body 17 and the reflecting mirror 16 constitute a reflecting body.

Next, a third explanation will be given of the operation of this embodiment configured in this way.
This will be explained with reference to the figures.

When the pulse motor 14 is rotated based on a certain initial setting, the same number of pulses as those given to the pulse motor 14 are sent from the pulse motor drive circuit 15 to the calculation unit 1.
3, and when the reflected light from the object to be measured Fa is detected by the photodetection sensor 4, the photodetection signal is input to the calculation unit 13, and the number of pulses when the reflected light enters the photodetection sensor 4 is calculated. N1 is detected by the calculation unit 23.

Here, it is assumed that the position of the object to be measured at the time when the number of pulses reaches N1 is the position Fa shown in FIG. That is,
Assuming that the distance in the horizontal direction in the figure from the light projectile 10 to the object to be measured Fa is a, the distance in the vertical direction is b, and the angle of incidence of the laser beam on the object to be measured is θ1, tan θ, -b/a The following relational expression holds true.

On the other hand, if the object to be measured moves by a distance X to the position Fb shown in Fig. 1, the incident angle of the laser beam becomes θ2, and the relational expression at this time is tan θ2 − (b + X) / a. Become. Note that the number of pulses from the start at the time of light detection at the Fb position is assumed to be N2.

Therefore, the displacement amount X is X-a(tan θ2-tan θI)−(1). Now, to simplify the explanation, assuming that the reflection angle of the reflection mirror 16 at the start is 0, θ1 is given by N1 as follows. That is, if the number of pulses corresponding to one revolution of the rotation shaft 14g of the pulse motor is No, then θ1-2πX(Nl/No) [Radian...
(2) becomes. Similarly, in the case of θ2, θ2 = 2 πX (N 2 / No)
[Radianco...(3) becomes.

Therefore, from the above, the displacement amount X is the number of pulses Nl.

It is given as a function of N2.

Therefore, in this embodiment, the calculation unit 13 detects the pulse numbers Nl and N2 before and after the movement of the object to be measured, respectively, and substitutes these detection results into the above equations (2) and (3), respectively.
1. Find θ2 respectively.

Then, the distance a and θ1θ2, which can be known in advance, are (1
), the amount of displacement X is obtained.

In this way, according to this embodiment, displacement detection is performed based on the number of pulses Nl and N2 that do not depend on the characteristics of light, so extremely high precision displacement detection is possible without being affected by temperature, light density, etc. can be done.

Furthermore, since the photodetection sensor 12 is used only to detect the incidence of light, the displacement detection accuracy is not directly affected by aging or drift of the photodetection sensor itself.

Furthermore, by arbitrarily setting the rotation angle per pulse, it is possible to measure a wide range from large displacements to minute displacements.

Further, since the initial settings and configuration in the calculation section 13 are performed digitally, it can be easily corresponded to a microcomputer, and work efficiency can be easily improved.

In the above embodiment, the reflector consisting of the rotating body 17 and the reflecting mirror 16 is rotated, but the inch warmer
The effects of the present invention can also be obtained by repeatedly moving it with a pusher or pusher.

FIG. 4 is a diagram showing an application example in which the present invention is applied to a level meter. Note that the same parts as those shown in FIGS. 1 and 2 are given the same reference numerals.

In this application example, a reflecting mirror 22 is provided on a cantilever beam 21 whose one end is supported by a fulcrum 20. A cam 23 is attached to the rotating shaft of the pulse motor 14,
This cam 23 is in contact with the movable end of the cantilever beam 21. The cantilever beam 21 is configured to perform reciprocating motion by the rotation of the cam 23. Reflection mirror 22 guides reflected light from laser light source 18 into tank 24 . A reflecting member 25 is floated on the liquid surface in the tank 24, and incident light entering from the entrance opening 26 is focused onto the reflecting member 25 by a projection lens 26 provided in the tank 24. The light reflected by the reflecting member 25 passes through the exit opening 28 and enters the light detection sensor 12 .

In the level meter configured in this manner, the reflection mirror 22 is moved back and forth in response to the rotation of the pulse motor 14, and the liquid surface is irradiated with reflected light with a constant stroke. Then, the amount of displacement of the liquid level is detected based on the number of pulses when the liquid level is different.

[Effects of the Invention] As detailed above, according to the present invention, displacement can be detected based on the number of pulses that does not depend on the characteristics of light, making it possible to measure displacement with extremely high precision and over a wide range. A displacement detection device can be provided.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of a displacement detection device according to an embodiment of the present invention,
Fig. 2 is a configuration diagram of the light projectile of the same embodiment, Fig. 3 is an explanatory diagram of the operation of the same embodiment, Fig. 4 is a diagram showing an example of application of the present invention to a level meter, and Fig. 5 is a Michael FIG. 6, which is a diagram of the principle of a Sonn type interferometer, is a schematic diagram of a conventional displacement detection device that utilizes a change in optical path. 10... Light projectile, 11... Condensing lens, 12...
- Light detection sensor, 13... Calculation unit, 14... Pulse motor, 15... Pulse motor drive circuit, 16...
Reflection mirror 17... Rotating body, 18... Semiconductor laser light source.

Claims (1)

[Claims] a light source that generates a laser beam; a reflector driven by an electrical pulse that irradiates the object to be measured with the laser beam from the light source; and a light receiving means that receives the reflected light from the object to be measured;
The number of pulses given to the reflector during the period from generation of the laser beam to reception of the reflected light is detected at each position before and after the movement of the object to be measured, and the number of both detected pulses is A displacement detection device comprising means for detecting the amount of movement of the object to be measured based on a change value of.