JPH0293317A - Optical displacement measuring apparatus - Google Patents

Abstract

PURPOSE:To measure the displacement of an object to be measured with high accuracy by cutting the return beam from the object to be measured by arranging a beam isolator on the beam path between a beam source and the object to be measured. CONSTITUTION:The laser beam emitted from an LD 11 is applied to an object 4 to be measured through a collimator lens 12, a beam isolator 22 and a projection lens 13. A part of the laser beam reflected and scattered from the surface of the object 14 to be measured is incident to a beam detector 16 through an image forming lens 15 and also incident to the beam isolator 22 through the projection lens 13. The reflected beam incident to the beam isolator 22 passes through a 1/4 wavelength plate 20 to be incident to a polarizing beam splitter 21 but, since the reflected beam passed through the 1/4 wavelength plate 20 crosses the polarizing direction of the laser beam from the LD 11 at a right angle, said beam is reflected by the polarizing surface of the polarizing beam splitter 20. By this method, the return beam from the object 4 to be measured is cut by the beam isolator 22 to control the oscillation state of the LD 11 stably to make it possible to measure the displacement of the object 4 to be measured with high accuracy.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical displacement apl determination device for optically determining the displacement of a limb 8-1 constant object.

[Conventional technology]

In recent years, the displacement of the object to be measured has been measured with high precision using laser light, etc. Optical displacement measuring devices that determine J have been developed and are used in various fields. This kind of non-contact displacement FAI
There are various types of I-determining devices depending on the measurement method.For example, 1
An optical displacement measuring device using the triangular fil ffl method as a 1?1 constant principle has a configuration as shown in FIG. In the figure, 1 is a laser diode (
(hereinafter abbreviated as LD), the laser light (measuring light) emitted from this LDI is irradiated onto the surface of a target object 4 via a collimator lens 2 and a projection lens 3.

Further, 6 is a photodetector that receives a part of the laser beam reflected and scattered on the surface of the target object 4 of 71-1 through an imaging lens 5, and the reflected light detected by this photodetector 6 is is converted into an electrical signal and input to a calculation section (not shown).

The optical displacement measuring device configured as described above is configured so that the light spot of the reflected light formed on the light receiving surface of the photodetector 6 through the imaging lens 5 corresponds to the amount of displacement of the object to be measured 4 as shown by the broken line. Move accordingly. Therefore, in the calculation section, the currents 11+12 flowing from both sides of the photodetector 6 are converted into voltages V 1 and V
2, (Vt-V2) / (Vl +V2
) by calculating the displacement Elx of the object to be measured 4
I'm looking for. Further, in the figure, 7 is a photodetector that detects the laser output of the LDI, and 8 is a controller that controls the laser output of the LDI via a drive circuit 9. The output of the photodetector is input to this controller 8. .

[Problem to be solved by the invention]

By the way, in such conventional optical displacement measuring devices,
Part of the laser beam reflected and scattered on the surface of the target object 4 passes through the projection lens 3 and the collimator lens 2.
When the reflected light from the object to be measured 4 returns to the LDI, the output of the LDl becomes apparently larger. Then, since the photodetector 7 detects this as the output of the LDI, the controller 8 is activated, causing the output of the LDI to fluctuate, resulting in a 7IN constant error. Note that this effect was more likely to occur as the surface of the object to be measured 4 was closer to a mirror surface.

The present invention has been made to solve these problems, and its purpose is to cut the return light from the object to be measured and to measure the displacement of the object with high precision. The present invention aims to provide an optical displacement i'l11 constant device.

[Means to solve the problem]

In order to solve the above problems, the present invention includes a light source that irradiates measurement light onto an object to be measured, and a photodetector that receives reflected light from the object to be measured via an imaging optical system. , an optical displacement measuring device comprising: a calculation unit that calculates the displacement amount of the object to be measured from the light spot position of the reflected light imaged on the light receiving surface of the photodetector; This is characterized by an optical isolator disposed on the optical path between the target and the target object.

[For production]

In the present invention, by disposing an optical isolator on the optical path between the light source and the object with A>1, the optical isolator can cut the return light from the object to be measured.

〔Example〕

Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a schematic configuration diagram of an optical displacement iljl setting showing an embodiment of the present invention.
The laser beam emitted from the Dll is irradiated onto the M1 constant object 14 via the collimator lens 12 and the condensing lens 13, and a part of the laser beam reflected and scattered on the surface of the object to be measured 14 is transferred to the imaging lens 15. The configuration is such that the light is received by the photodetector 16 via the photodetector 16.

Then, the reflected light received by the photodetector 16 is converted into an electrical signal and inputted to a calculation section (not shown), and the reflected light is imaged on the light receiving surface of the photodetector 16 through the imaging lens 15 as described above. It is configured to calculate the displacement aX of the object to be measured 14 from the light spot position.

An optical isolator 22 composed of a quarter-wave plate 20 and a polarizing beam splitter 21 is disposed between the collimator lens 12 and the projection lens 13. Return light from the fixed object 4 is cut off. Note that the LDl is controlled by the controller 18 via the drive circuit 19, and the controller 1
8, the output of the first detector 17 is input.

Next, the operation of the optical displacement Jl determination device configured as described above will be explained.

The laser beam emitted from the LDll passes through the collimator lens 12.
, is irradiated onto a fixed object 14 via an optical isolator 22 and a projection lens 13. A part of the laser light reflected and scattered by the surface of the object to be measured 14 enters the photodetector 16 via the imaging lens 15, and
The light enters the optical isolator 22 via the projection lens 13. The reflected light that has entered the optical isolator 22 passes through the quarter-wave plate 20 and enters the polarizing beam splitter 21, but the reflected light that has passed through the quarter-wave plate 20 has a polarization direction of LD.
Since it is perpendicular to the polarization direction of the laser beam from II, it is reflected by the polarization plane of the polarization beam splitter 20. As a result, the return light from the object 4 to be measured 41 can be cut off by the optical isolator 22, so the oscillation state of the LD 11 can be stably controlled, and the displacement of the object 41 to be measured can be controlled at 8-1 with high precision. can be determined.

Note that the present invention is not limited to the above embodiments,
Various design changes are possible without departing from the scope of the claims. For example, in the above embodiment, the optical isolator 22 is disposed between the collimator lens 12 and the light projection lens 13, but the light projection lens 13 and the light projection lens 11 are
It may be arranged between the p1 constant target object 14, in short, the LDl
It is only necessary to dispose it on the optical path between L and the object to be measured 14. In addition, although laser light was used as the measurement light in the above embodiment, when using a non-polarized light source such as a point light source, a polarizing plate is provided between the light source and the optical isolator so that the light enters the polarizing beam splitter 20. If the light is a polarized beam, then he, 17
Return light from a constant object can be cut by an optical isolator λλ.

〔Effect of the invention〕

As explained above, the present invention includes a light source that irradiates measurement light onto an object to be measured, a photodetector that receives reflected light from the object to be measured via an imaging optical system, and a photodetector that receives the light reflected from the object to be measured via an imaging optical system. In an optical displacement measuring device, the light source and the object to be measured are provided with an arithmetic unit that calculates the amount of displacement of the object to be measured from the position of a light spot of reflected light that is imaged on a light receiving surface of a detector. Since the optical isolator is disposed on the optical path between the two, it is possible to cut the return light from the object to be measured, and it is possible to provide an optical displacement measuring device that can measure the displacement of the object to be measured with high precision.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of an optical displacement 3-1 fixing device showing an embodiment of the present invention, and FIG. 2 is a schematic diagram of a conventional optical displacement i1-1 fixing device. 11...LD (light source) 12...Collimator lens, 13...Light projection lens, 14...Measurement object, 15...Imaging lens, 16...Photodetector,
17... Photodetector, 18... Controller, 19... Drive circuit, 20... 1/4 wavelength plate, 21
...Polarizing beam splitter, 22...Optical isolator

Claims (1)

[Claims] A light source (11) that irradiates measurement light onto the object to be measured (14)
a photodetector (16) that receives reflected light from the object to be measured (14) via an imaging optical system (15); In the optical displacement measuring device, the optical displacement measuring device is equipped with an arithmetic unit that calculates the amount of displacement of the object to be measured (14) from the light spot position of the reflected light. An optical displacement measurement device characterized by having an optical isolator (¥22) disposed on the optical path between them.