RU1825968C - Laser interferometer - Google Patents

Abstract

The invention relates to measuring technique, and specifically to interference measurements, and can be used to determine linear displacements as well as refractive indices of liquid and gaseous media. The purpose of the invention is to improve the accuracy of measurements. A polarized light beam passing through a quarter-wave plate becomes circularly polarized; on a polarization beam splitter, it is divided into two light beams of equal intensity and having orthogonal polarizations. On the polarization beam splitter, each of the rays returned by the corner reflectors is divided into two with the same intensities, and pairs of light beams having the same polarization interfere. After passing through the polarizers, the interference fields are read, which allows for high measurement accuracy. 1 ill. 6

Description

The technical solution relates to measuring equipment, and in particular to optical-physical measurements, and can be used for precision measurements of linear displacements, speed, acceleration, vibrations, changes in the refractive indices of transparent media, etc.

The aim of the invention is to improve the accuracy of measurement.

. The drawing shows a block diagram of an interferometer.

It consists of a laser 1, on the radiation path of which a quarter-wave plate 2 and a polarizing beam splitter 3 are installed. The measuring arm is formed by a linear phase plate 4 and an angular reflector 5, and the supporting arm is formed by a linear phase plate 6 and an angular reflector 7. On the path reflected by angular Reflectors 5 and 7 of the rays (at the output of the interferometer) are equipped with two polarizers 8 and 9.

The laser 1 is made with a linear polarizer, the quarter-wave plate 2 is mounted so that its optical axis

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oriented at an angle of 45 ° to the plane of incidence of the light beam on the beam splitter.

The interferometer operates as follows.

A collimated linearly polarized light beam from the laser 1, passing through the quarter-wave plate 2, becomes circularly polarized. On polarized beam splitter 2, it is divided into two light beams of equal intensity and having orthogonal polarizations. In the measuring arm, the light beam passes through the linear phase plate 4, the corner reflector 5, and returns back to the polarization beam splitter 3. The polarization is also converted from linear to circular. Similar happens in the supporting shoulder. Here, the light beam passes through the linear phase plate 6, the corner reflector 7, and returns to the polarization beam splitter 3. On the polarization beam splitter, each of the rays returned by the corner reflectors is again divided into two with the same intensities and pairs of light beams having the same polarization, interfere. After passing through the polarizers 8 and 9, the interference fields are read in one of the known methods.

The radiation intensity at the output of a two-beam Mayuelson-type laser interferometer can be represented as:

(L) -li + l2 + .2 Vh | 2 cos (L),

where And and la are the intensities of the interfering first and second beams, p (L)

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2nL ... - 1-, (L) is the travel difference in the arms of the interferometer;

A is the laser wavelength. Following (3), we write the expression for the minimum root mean square error of the measurement of the path difference L

b (A

 d

where a a

- fe - electron charge,

F is the frequency band, ftp k (h + Iz); K is the coefficient of proportionality, K

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k -y 1 - the ratio of the maximum intensity of the interfering beams to the minimum).

From this expression it follows that the accuracy of measuring the phase of the interference signal depends on the contrast of the interference signal K.

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Claims (1)

The claims A laser interferometer comprising a laser, sequentially mounted a beam splitter on the measuring and supporting arms, each of which includes a linear phase plate and an angular reflector and two polarizers mounted respectively at the output of the interferometer, characterized in that, in order to improve the accuracy of measurement, it is equipped with a quarter-wave plate mounted between the laser and the polarization beam splitter. ( in I D)