SU1260674A1 - Interferometer for measuring linear and angular displacements of object - Google Patents

Abstract

The invention relates to a measurement technique, in particular, to interferometers for measuring linear and angular movements of an object. The purpose of the invention is to simplify the design of the interferometer by simplifying the beam splitter unit and its location. The interferometer contains successive monochromatic radiation sources, a light-transmitting unit made in the form of a tetrahedral prism, optically coupled with it two corner reflectors and a photoelectric receiver. A translucent coating is applied on one smaller face of the prism, a mirror coating is applied on the other smaller face and one of the larger faces. The smaller faces of the prism are non-parallel, the angle between THEM is 0 1/2 tf-arcsinx (sincf / n), where If is the acute angle between the smaller edge with a translucent coating and the larger edge of the prism, and n is the refractive index of the prism material. The prism faces the radiation source with a smaller edge with a translucent coating, and the angle between the optical axis of the radiation source and the normal to this smaller face is equal to the acute angle Cf. When changing the path difference in the interferometer, the amplitude modulation of the light flux incident on the photoelectric receiver occurs, and by changes in the photocurrent, one of the reflectors is displaced (in the case of measuring linear displacement) or the angular position of the object (when both corner angles are set to turning object), 1 Il. (L o od k ff

Description

The invention relates to a measurement technique, in particular, to interferometers for measuring linear and angular movements of an object.

The purpose of the invention is to simplify the design of the interferometer by simplifying the beam splitter and its location.

The drawing shows a schematic diagram of an interferometer for measuring linear and angular displacements of an object.

The interferometer contains a source of monochromatic radiation, a light-separation unit made in the form of a tetrahedral prism 2, two corner reflectors 3 and 4 optically connected with it, and a photoelectric receiver 5. On one smaller face 6 of the prism 2 a semitransparent coating is applied, on the other The smaller face 7 and one of the larger faces 8 are coated with a mirror coating. The smaller faces 6 and 7 are non-parallel, the angle between them is equal to

If, / zgpch L 6 2 arcsinl. {

where tf is the acute angle between the smaller

a face with a translucent coating and a larger prism edge;

And - the refractive index of the material of the prism.

The prism 2 faces the radiation source 1 with a smaller edge 6, and the angle IP between the optical axis of the radiation source 14 and the normal to the smaller edge 6 is equal to the acute angle (between the smaller edge 6 and the larger edge 8.

The interferometer works as follows.

The luminous flux from the source 1 of monochromatic radiation, for example, the Hg-Ng Laser, is divided into two beams by the beam-splitting face 6 of the prism 2. One of the resulting beams is directed to the reflector 3, and its direction of propagation is normally reflecting the larger face 8 of the prism 2 only in that case when the angle oi is equal to the angle o-; 3 (as angles with mutually perpendicular sides) and oi, 1 odj a ;, cf (1). .

The second beam is refracted by the beam-splitting face 6 and passes to the reflecting smaller face 7 of the prism, which directs it to the reflector 4. In order for the second light to

the beam met with a larger face 8 having a mirror coating, at a right angle, it is necessary that the equality SU, c (angles with mutually perpendicular sides) be fulfilled. Since the angle равен, is equal to the angle ω; then, & Since both light beams are perpendicular to the larger face 8 with a mirror coating, the equality ftig + oi, (3) (opposite angles) or 2 0 is true (taking into account formula (2). Since odj of - (X (4), and os.,,,

 arcsin (---) (5), where P is the refractive index of the prism material, then from (1) - (5) we get

. , 31PYCH-. “. ,,

c, + arcsin (- j) 2,6j- (6)

In this case, the angle between the smaller faces 6 and 7 of the prism 2 is equal to

 and, -

. , S inoC.x оС, - arcsin (--- V

1G. xSinCffl ,, jUf-arcsin (---) J. (7)

Thus, while ensuring the equality of the angle of incidence of the light beam on the beam-splitting face 6 of the prism with an acute angle cp between the larger edge 8 of the prism 2 and its smaller edge 6 and the equality of the angle between the smaller faces 6 and 7 of the prism with angle 0 from expression (7), it is not only the respective rays are strictly parallel, but also perpendicular to the latter, reflecting the larger face 8, which plays the role of an autocollimating mirror.

Thus, parallel light beams emerging from prism 2, reflectors 3 and 4 are directed to a larger reflecting face 8 of prism 2, reflected from it, reflectors 3 and 4 pass in the opposite direction and are aligned on the beam-splitting face 6. Next, the luminous flux enters the photoelectric receiver 5. When the path difference changes in the interferometer, the amplitude modulation of the light flux incident on the photoelectric receiver 5 occurs and, by changing the photocurrent, one of the reflectors 3 and 4 is displaced (in the case of measuring movement) or on the angular position of the object (when installing both corner reflectors 3 and 4 on the rotating object). The fragile value (f is selected from the conditions for ensuring passage in a prism with a given aspect ratio of 2 / L of a light beam of a given diameter, taking into account the deflection at refraction at the beam-splitting face- 6.

Formula

the invention

An interferometer for measuring the linear and angular displacements of an object, containing successively located sources of monochromatic radiation, a beam splitting unit, two corner reflectors optically connected to it, and a photoelectric receiver, the beam splitting unit is made in the form of a tetrahedral prism, one of which has a semi-transparent coating applied on one of its smaller edges.

ten

and on the other smaller face and one of the big faces facing the corner reflectors there is a mirror coating, characterized in that, in order to simplify the design, the prism is filled with non-parallel smaller faces, the angle between them is:

„If. xsinffvl 0 5 M -arcsLn () J,

where Cf is the acute angle between the smaller

a face with a translucent coating and a larger face 15 of the prism;

n is the index of the prism material, 1 is installed so that its smaller face with a translucent coating 20 faces the radiation source, and the angle between the normal to this face and the optical axis of the radiation source is equal to the angle (f.

Compiled by L.Lobzova Editor N.Gorvat Tekhred L.Oleinik Proofreader M.Samborska

Order 5214/36 Edition 670 Subscription

VNIIPI USSR State Committee

for inventions and discoveries 113035, Moscow, Zh-35, Raushsk nab., 4/5

Production and printing company, Uzhgorod, Projecto st., 4

Claims (1)

Claim An interferometer for measuring linear and angular displacements of an object, containing a sequentially located source of monochromatic radiation, a beam splitting unit, two corner reflectors optically coupled to it, and a photoelectric receiver, the beam splitting unit is made in the form of a tetrahedral prism, on one of its smaller faces a translucent coating is applied, equal to Θ = -arcsin (--—)], where. q is the acute angle between the smaller face with a translucent coating and the larger face of the prism; η is the refractive index of the prism material, I prism is installed so that its smaller face with a translucent coating faces the radiation source, and the angle between the normal to this face and the optical axis of the radiation source is equal to the angle (f.