SU1416861A1 - Interferometer for measuring linear displacements of objects - Google Patents

Abstract

The invention relates to a measurement technique, namely, instruments for measuring displacements and lengths of an object, and can be used in instrument engineering, precision engineering. The aim of the invention is to improve the measurement accuracy by increasing the number of measuring segments. To achieve the goal, two orthogonal-polarized beams are formed. Each beam is directed to a corresponding light-returning system made in the form of three corner reflectors, one of which is mounted on the carriage associated with the object, and flat mirrors are mounted on the bisectors of the other two. The distance S between the normals of flat mirrors is determined by the formula 5 8b-4d / n + 8, where b is the distance from the edge edge of the corner reflector to the bisector of its right angle; d is the width of the light beam; n is the multiplication factor of the optical path difference of light rays. After converging the beams at a carriage offset, the interference fringes shift. The counting of interference fringes and the direction of their displacement is carried out in an electronic unit containing photodetectors and a reversible counter. 4 il. with $ (L with

Description

05 00 SP)

The invention relates to a measurement technique, namely to instruments

; to measure displacements and object lengths, and can be used in instrument making, precision engineering, as well as in metrological laboratories xp

The purpose of the invention is to improve the measurement accuracy by increasing

; number of measuring segments

: and reduce the sensitivity of the interferometer and the indirect moldedness of the carriage movement,

I FIG. 1 shows the functional

: at the right of the interferometer to produce a linear motion of the object; in FIG. 2 - retroreflective

system on fkg. 3 is the same; the view is barely Baj in FIG. 4 is a block diagram of a photoelectron unit.

: Iner4) an erometer for measuring object displacement contains

coherent light source 1, mounted downstream, first emission

: A 1 2 7, / 8 bit and a 3 system for times: beam division, which is optically coupled to mirrors 4 and 5, a second 6L / 8 gushastinka, which is optically connected to a mirror 75 and a second system 8 for onion separation the mirror 9 with which is optically connected, two polaroids 10 and ll are optically connected with system 8 for separating the beam and the mirror 9, the photoelectronic unit 12, whose inputs are optically connected with the polaroids 10 and 11 carriage 13., where the return light of the system 14 and 15 installed in each branch of the interferometer, one of which is optically coupled to a 5 a mirror a - with a zirkgsh 7 each light-returning system and 15 consisting of an angled reflector 16 (17) fixed on the carriage 13, two corner reflectors 18 (19) and 20 (21), mirrors 22 (23) and 24 (25) optically coupled to the corner reflector 16 (17) and thus mounted. that the edges of the corner reflectors 18 and 20 (19 and 21) of the perpendiculars of the edge of the corner reflector 16 (17) s of the bisector of right angles are shifted parallel to one another by distance S, determined by the formula

t п + 8

where b is the distance from the edge edge

corner reflector 18 (19) to the bisector of its right angle;

d is the width of the light beam; n is the multiplication factor of the optical path difference of light rays,

and the middle of the mirrors 22 (23) and 24 (25) are on the bisectors of the right angles of the yroj-iKOBMX reflectors 18 (19) and 20 (21),

The optical axes of Gshastinsk 2 and 6 / B are parallel to the nXiOCKocTH polarization of a beam of coherent light emanating from source 1. The optical plane of one of the polaroids Yu is parallel to the plane of polarization of one of the orthogonal rays of the light that fell on it „a the optical plane of the polaroid 11 is perpendicular to the optical plane of the polaroid 10. The systems 3 and 8 for dividing the beam are designed in such a way that they break the light beam on them into two rays of light of the same intensity,

S

FIG. Figures 2 and 3 show the position of the corner reflectors and mirrors in the light-transmitting system-. Reflectors 18 and 20 are made on a single base, which is an angular reflector, by applying one half of its face to a reflecting layer, the thickness of which lies within

from

-J2 (8b-4d) -J 2 (8b-4d)

and the area parallel to {the edge from the edge of the face is made transparent for the light beam and has 7, col i, equal to the edge, and the width determined by the formula

J G2 ().

In order not to distort the entrance of the light beam B to the retroreflecting system, the width of the mirrors 22 (23) and 24 (25) must not exceed four distances S.

The photoelectric unit 14 (Fig. 4) contains photodetectors 26 and 275 whose inputs are optically connected to the polaroids 10 and 11, respectively, and the codes are electrically connected to the input of the moving direction determining unit 28 and the output of the photoreceiver 26 is also connected to one kg the inputs of the reversible counter 29, the second

31

the input of which is connected with the output of block 28. The output of the reversible counter 29 is the output of the interferometer.

The interferometer works as follows.

The beam from the source, coherent light passes through the plate

2 L / 8, resulting in the formation of two orthogonally polarized optical signals, is split by system 3 to divide the beam into two beams; One of these rays is mirrors

4 and 5 is directed to the retroreflective system 14 of the first interferometer branch and returns to the system

3d split beam and second

the beam is directed by the mirror 7 to the light returning system, 15 of the second branch of the interferometer and also returns to the system 3, passing twice the plate 6, which leads to an additional shift of the orthogonal components of the light beam one relative to

Q

The other in phase is 90. In system 3, both beams of light interfere. The received optical signal is divided into two beams by the second system 8 for beam separation, one of the beams is directed to one of the polaroids 10, and the second mirror 9 to the polaroids 11. The polaroids Yu and 11 separate each of their orthogonal components the light beam and direct it to its photodetector 26, 27 of the photoelectric unit 12.

Photodetectors 26 and 27 convert optical signals into sequences of electrical pulses that are shifted 90 degrees relative to each other in phase, which is necessary for reversing the counting of light bands, depending on the direction of movement of the carriage 13, together with reflectors 16 and 17, this shift is either positive or negative. The desired carriage offset is determined by the number of light strips and sign.

Claims (2)

1. An interferometer for measuring the linear displacements of an object containing a sequentially installed light source and a system for separating a light beam from a source into two branches, in one of which two mirrors and the first light reflecting system are installed and optically connected 6861 in the form of two corner reflectors; in the other, a mirror and a second retroreflective system, similar to the first, are installed and optically coupled to an object that has one corner reflector from each branch, a second 1Q system for dividing the light beam, an input which is associated with the outputs of the retroreflective systems of both branches, and photoelectric; a block whose inputs are connected to the outputs of the second g systems for separating light a beam, characterized in that, in order to improve the measurement accuracy, it is equipped with a plate of 1/8 wavelength, installed between the point of light and the first system for separation of the beam, by the second plate of 1/8 wavelength, installed in one of the branches along the radiation path in front of the mirror, by two analyzers, w installed in front of the corresponding inputs of the photoelectronic unit, two additional corner reflectors installed respectively in each light reflecting system so that the edge of one of the axis of the corner reflectors parallel to the edge of the additional corner reflector, the corner of the corner reflector mounted on the carriage is perpendicular to the edge an additional corner reflector, and four mirrors mounted in pairs on the right angles of the right angles of each pair of the main and additional reflectors, and the distance S between the bisectors of the right angles of these corner reflectors is chosen from the ratio 45   Sbzld n + 8. where b is the distance from the edge edge corner reflector to the bisector of its right angle; gQ d is the width of the light beam; n is the multiplication factor of the optical path difference of light rays, 2. The interferometer according to claim 1, d and 55 is characterized in that, in order to simplify the design, each pair of primary and secondary corner reflectors is installed on a common base, which represents the corner reflector is half-transparent and has a length equal to the length of one of the faces of which the edges are applied to the edges, and the width defined by the reflective layer, the thickness of which is 5 (25 + d), lies within from -G2 () -IzCSb-Ad) QJ, P / -, is opaque and has a length equal to the length of the edge, and the width determined by the formula (25 + d), where o is the distance between bisectors 0 sixteen t2.g. 23 (22 S (2 ) fig.z