RU1800259C - Interferometer for measuring linear displacements of objects - Google Patents

Abstract

The invention relates to a control and measuring technique, to interferometric measurements of linear displacements of objects. The purpose of the invention is to increase information content by measuring displacements in two directions. For this, the interferometer is equipped with an optical element designed to change the direction of the radiation beams installed between the diffraction modulator and the beam splitter, a half-wave phase plate, a collimator, a polaroid, a second polaroid, a third beam splitter installed between a beam splitter and a polaroid, a second collimator, and a fourth beam splitter , a second reflector, a third polaroid and a third photodetector, forming a second working channel, and the beam splitter is made with a polarization coating. An optical element designed to change the direction of the radiation beams can be made in the form of a prism or in the form of optical wedges. 2 s.p. f-ly, 1 ill. AND

Description

The invention relates to instrumentation, to interferometric measurements of linear displacements of objects.

An object of the invention is to increase information content by measuring bi-directional movements.

The drawing shows a diagram of the proposed interferometer.

The interferometer comprises a two-frequency linearly polarized radiation laser 1, a diffraction phase modulator 2, for splitting the laser radiation into two beams, an optical element 3, for changing the direction of the radiation beams, a half-wave phase plate 4, mounted on the path of one of the radiation beams , reflector 5, a beam splitter 6, having a polarization coating, two collimators 7, two polarization beam splitters 8, two fixed corner reflectors 9, two movable corner reflectors 10 mounted on the measurement objects, poloid 11 installed in the reference channel, two poloid 12 installed in the working channels, a photodetector 13 installed in the reference channel, two photodetectors 14 installed in the working channels, and a beam splitter 15, intended to form a reference channel. Collimators 7, polarization beam splitters 8, fixed corner reflectors 9, movable corner reflectors 10, polarity 12 and photodetectors 14 are installed one in each of the two working channels. The optical element 3 can be made in the form of a prism or in the form of optical wedges.

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The interferometer operates as follows.

Laser 1 generates a beam of radiation consisting of two waves with different frequencies w and w and orthogonal linear polarizations. Modulator 2 splits this beam of radiation into two beams directed at an angle to one another. Each of these beams contains two orthogonal polarized waves. In this case, one beam has the frequencies oh and wi, and the other has the frequencies 0) 2 and a) 2. The optical element 3 changes the directions of the radiation beams to mutually parallel. After element 3, one of the radiation beams passes through a half-wave plate 4, which rotates the plane of polarization of each wave by 90 °. The second beam hits the reflector 5, mounted at an angle to its axis, and, reflected from it, intersects with the first beam on the beam splitter 6.

A beam splitter 6 having a polarization coating separates the radiation components of each beam incident on it by polarization and forms two combined radiation beams with orthogonal polarizations, while one of the radiation beams has frequencies w and, and the other has frequencies w and , odg. Each beam of radiation can be used in an independent working channel. To form the reference channel, an additional beam splitter 15 is installed in the path of one of the beams, separating a part of the beam and directing it to the poloid 11 and photodetector 13. This reference channel can operate on both working channels.

In each working channel, the radiation beam is directed through the collimator 7 to the polarization beam splitter 8, which separates the radiation components by polarization, and thereby frequency, directs the radiation from one of the frequencies to a fixed angle reflector 9, and with a different frequency to the movable corner reflector 10. After the reflectors 9 and 10, the beams in the beam splitter 8 are combined and sent through the poloid 12 to the photodetector 14, which at the output generates an electrical signal whose frequency is different from the reference one and carries information on the movement of the corner reflector 10.

In the proposed interferometer, a two-frequency radiation beam with a high frequency difference is converted into two radiation beams, each of which consists of two waves with orthogonal linear polarizations and a frequency difference specified by a modulator. The use of radiation beams with a given frequency difference in an interferometer, in contrast to a beam with a high frequency difference, does not require complicated expensive electronics for

signal conversion. In this case, it is possible to use the radiation of a two-frequency laser to form two working channels in the interferometer and to measure displacements in two directions.

FORMULA AND ZOBRETE N and

Claims (3)

1. An interferometer for measuring linear displacements of objects, comprising a two-frequency linearly polarized laser and a diffraction phase modulator located along the radiation beam, splitting the laser radiation into two beams, a first beam splitter and a photodetector forming a reference channel, a reflector installed between diffraction modulator and a first beam splitter, a second beam splitter, a reflector mounted on the object, and a second photodetector forming a working channel, characterized in that, with in order to increase the information content by measuring the bi-directional movement, it is equipped with an optical element designed to change the direction of the radiation beams installed between the diffraction modulator and the first beam splitter, a half-wave phase plate mounted between the optical element intended to change the direction of the radiation beams, and the first beam splitter, a collimator, installed in the working channel between the first and second beam splitters, a poloid installed in the reference channel between the first beam splitter and the photodetector, a second poloid installed in the working channel between the second beam splitter and the second photodetector, a third beam splitter installed between the first beam splitter and the poloid a second collimator, a fourth beam splitter, a second reflector mounted on the object, a third poloid and a third photodetector, forming a second working channel, and the first beam splitter The plug is made with a polarization coating. 2. The interferometer according to claim 1, wherein the optical element for changing the direction of the radiation beams is made in the form of a prism. 3. The interferometer according to claim 1, characterized in that the optical element designed to change the direction of the radiation beams is made in the form of optical wedges.