JPS5871401A - Device for measuring minute displacement - Google Patents

Abstract

PURPOSE:To measure the minute displacement of an object to be measured highly accurately by combining two semiconductor lasers and a polarizing beam splitter, and measuring the frequency when the light outputs from the reverse surfaces of the lasers are varied by displacement. CONSTITUTION:Lenses 16 and 17 are provided between semiconductor lasers 11 and 12 and the polarizing beam splitter 13. The light beams from the reverse surfaces of the lasers 11 and 12 are received by light receiving elements 14 and 15. Laser light beams L1 and L2 from the lasers 11 and 12 are synthesized by the beam splitter 13 and irradiated on the object. The reflected light beam is recombined to the lasers 11 and 12 through the splitter 13 and the lenses 16 and 17. The laser outputs from the reverse sides are detected by the light receiving elements 14 and 15. When the object is displaced, wavering of the light output occurs. Since the frequency of the laser output is inversely proportional to the distance to the object, the frequency when the wavering occurs is measured, and the distance to the object is measured by a specified expression. Therefore the displacement of the body can be detected highly accurately.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a minute displacement measuring device using a semiconductor laser, and an object of the present invention is to provide a minute displacement measuring device that can measure minute displacements of an object to be measured with high precision.

FIG. 1 is a diagram illustrating the principle of a means for measuring minute displacements using a semiconductor laser. In the figure, (1) is a semiconductor laser, (2) is a light receiving element, (8) is a lens, and the mouse is an object to be measured. When the projected and reflected light is recombined to the semiconductor laser (1), fluctuations occur in the optical output whose fundamental frequency is inversely proportional to the round-trip propagation time between the object to be measured M and the semiconductor laser.

That is, assuming that the speed of light is 0, the refractive index of the medium is 0, and the distance between the semiconductor laser and the object to be measured is D, the frequency f of the laser laser output P is as follows. (However, M=1.2...), therefore,
If the frequency #kf of the laser output P is measured, the path s
1D, and therefore the displacement of the object to be measured M can be measured.

The present invention is based on the above-mentioned principle and uses a combination of two semiconductor lasers and a polarization separation element to enable highly accurate measurement of minute displacements of an object to be measured.

An embodiment of the present invention will be described below with reference to the drawings.

In Fig. 6, 0 power, 4 is the semiconductor laser, (to) is the above-mentioned amphibodiconductor laser Uυ, and (b) laser beams with mutually perpendicular linear polarization: [Jl sIIm are synthesized to produce the measured object M. A polarization beam splitter, such as a polarization beam splitter, is used to irradiate the beam. ) and (to) are light receiving elements that receive the light output from the opposite surface of each semiconductor laser (9) and H during recombination. It consists of (b) and v) are each semiconductor laser αυ
.

This is a lens interposed between (b) and the polarizing beam splitter (to).

Next, the operation of the above configuration will be explained.

When the laser beams In e Lm output from each main surface of the semiconductor lasers αυ and 4 are input to the polarizing beam splitter (to), these laser beams ``1 sI'l are input to the polarizing beam splitter (to). The synthesized object to be measured Mfl;
4A shot. When the light reflected by the object to be measured M passes through the polarizing beam splitter (to) and each lens 06), (b), and is recombined to each semiconductor laser (■), 0@,
Laser output from the opposite surface of each semiconductor laser (6), (to) is taken out by a light receiving element -, 1X51. At this time, the frequency of the laser output from each half-four body laser (6) and the hook (considering only the first order) is f, c = □ ... (2) 2n (j +
+ DM) f snow = □
... (8) 2nCAm 1DM) (4th session) Here, 4*J! is the distance from each semiconductor laser U, aS to the center of the polarizing beam splitter, and DM is the distance from the center of the polarizing beam splitter to III &
#This is the distance to the constant M. (2), (II
), from the center of the polarizing beam splitter to the object M
The distance lIADM is given by the following equation.

f goose AM ft4 D1=□□ ... (4) f goose - f snow Therefore, since t, , t, &i are known, by measuring 'ls'l, the distance l to the object to be measured is obtained! ! (The displacement Ltll can be measured accurately.

In addition, in the *m example above, each semiconductor laser (b), (b)
The explanation has been given using an example in which the output detection means is composed of the light receiving element α which receives the optical output from the opposite surface of the semiconductor laser (11). The output detection means may be replaced by a detection means (not shown).

Although the two semiconductor lasers according to the above embodiment may have the same wavelength, it is preferable to use lasers with different wavelengths in order to avoid mutual interference.

Furthermore, the polarization separation element (to) may be, for example, a polarization prism other than a polarization beam splitter.

As described above, this invention enables measurement by combining two semiconductor lasers and a polarizing beam splitter! 11
A highly accurate micro displacement measuring device can be easily obtained.

[Brief explanation of drawings]

Figure 1 shows the minute displacement f of the measured object using a semiconductor laser:
2 is a diagram showing the relationship between the optical output and frequency of the semiconductor laser shown in FIG. 1, and FIG. 6 is a diagram showing an example of the minute displacement measuring device S according to the present invention. Figure j, 4th
The figure is a diagram showing the relationship between the optical output of the semiconductor laser and the frequency in the apparatus of FIG. 3. (11) 4. Semiconductor laser, . . . Polarization separation element, (B) Q. Lens, . . . Output detection means, M. Object to be measured. Note that the same reference numerals in the figures indicate the same or corresponding parts. Agent Makoto Kuzuno (1 other person) Figure 1 Figure 2 11) d4j So

Claims (1)

[Claims] (1) Two semiconductor lasers, a polarization separation element that combines linearly polarized laser beams output from the main surfaces of these semiconductor lasers and irradiates the object to be measured, and each of the semiconductor lasers and the polarization separation element. and an output detection means for detecting a change in the optical output from the opposite side of the single-chip semiconductor laser that receives the reflected light from the object to be measured or a change in the terminal voltage of the laser. Micro displacement measuring device.