SU365677A1 - - Google Patents

Description

The authors

S.A. Korotkoi and V.F. Martynov inventions

For the visitor

BIBL /

DEVICE FOR DETERMINATION OF POLARIZED LIGHT BEAM DISPLACEMENT

one

The invention relates to devices using the effect of rotating the plane of polarization of the beam, and can be used in engineering surveying.

A device for determining the movement of a polarized light beam is known, comprising a receiving cell of varying thickness, made of a substance that rotates the plane of polarization, rotating the polar-iroid, photo receivers and phase-measuring device.

In order to increase the resolution, automate the measurements and enable the received beam to be used both as an analyte and as a reference, the cuvette in the proposed instrument, receiving polarized light and having a variable thickness, is made in the form of two halves made of substances having the same refractive indices, and one of the halves of the cuvette is made of a substance that rotates the plane of polarization.

The block diagram of the described device is shown in the drawing. Flat-plane radiation from the emitter (the laser passes through the cuvette (wedge), the 1st section2-2, ysg isolated from substances rotating the polarization plane (section 2) and does not rotate the plane of polarization (section 2), but having

the same refractive index with the substance in section 2. Next, the radiation is focused by a cylindrical lens 3 and, by separating diaphragm 4 into two beams / and 1, passes through the polaroid 5, filter 6, is focused by lenses 7 and goes to photodetectors 8 from which electrical signals are applied to the amplifiers 9, 10, the phase detector 11 and the indicator 12. Based on the readings of the latter, the magnitude of the displacement of the beam is judged.

Poloid 5 is rotated by the electric motor 13.

The splitting of the beam / into two (/ and 1) is necessary to obtain the phase difference on the photodetectors, resulting from the rotation of the plane of polarization of the beam that has passed section 2.

The magnitude of the signals on the photodetectors 8 can be represented as:

t, -cos (cf),

(1) E, E,.,

the signals on the photodetectors 8; the magnitude of the signals to the polaroid 5; . -.

angular velocity of rotation of the floor roid 5; time;

Ф is the phase shift of signal E, relative to signal 2, caused by the rotation of the plane of polarization of the beam.

The phase shift φ, in turn, can be expressed in the form

F / S, th or

, -a-igo., (2)

where / Ci - coefficient taking into account the specific rotational ability of the substance;

b is the optical path length of the beam in the substance of the cuvette 2;

a is the angle at the cuvette's vertex;

a is the magnitude of the beam displacement along the cuvette.

From expression (2), it can be seen that at constant x / Ci and a, the phase shift of the signals on the photodetectors is directly proportional to the magnitude of the beam displacement along the cell. The speed of the system can be significantly increased if poloid 5 is left stationary and an electro-optic modulator is placed in front of it (Kerr cell, etc.).

The permissive ability of the device depends on the rotational ability of the substance (/ Ci) and the method of indicating the phase shift between the beams.

Subject invention

A device for determining the movement of a polarized light beam containing a receiving cell of variable thickness, made of a substance that rotates the plane of polarization. The breeder polaroid, photodetectors and phase-measuring device, characterized in that, in order to increase resolution, automate measurements and ensure that the received beam can be used both as an analyte and as a reference, the cuvette of variable thickness is made in two halves made of substances that have the same refractive indices, and one of the halves of the cuvette is made of a substance that rotates the polarization plane.