SU1663453A1 - Temperature measuring device - Google Patents

Abstract

The invention relates to thermometry, namely, devices for remote temperature measurement under conditions of strong electromagnetic fields. The purpose of the invention is to improve the accuracy of temperature measurement. A device for measuring temperature contains a source of monochromatic radiation, which is optically coupled through a fiber to the input of a thermal converter. The thermal converter is made in the form of a series of alternating birefringent plates and polarizers, with the optical axis of each birefringent plate oriented at a 45 ° angle with respect to the orthogonal oriented main directions of the polarizers between which it is located. The output of the thermal converter through the optical fiber is optically coupled to the selective receiver. The thickness of the birefringent plates is chosen according to the condition of matching the angular aperture of the fiber with the angular distance between the isochromates. 1 il.

Description

The invention relates to thermometry and is intended for remote temperature measurement in conditions of strong electromagnetic fields.

The purpose of the invention is to improve the accuracy of temperature measurement.

The drawing shows a block diagram of a device for measuring temperature,

The device contains a source of monochromatic radiation, a first light guide 2, a thermal converter 3, polarizers 4, birefringent plates 5, a second light guide 6, a selective receiver 7. The optical axis of each birefringent plate 5 is oriented at an angle of 45 ° relative to the orthogonally oriented main direction m polarizers 4, between which it is located,

The device works as follows.

Thermal converter 3 is installed on an object whose temperature is measured. When measuring the temperature of an object, the linear dimensions of the birefringent plates 5 change, and consequently, the optical path lengths change for ordinary and extraordinary rays in an anisotropic medium. A change in the optical path lengths for ordinary and extraordinary rays leads to a change in the phase shift between orthogonally polarized waves at the output of each birefringent plate 5, t, e to change the polarization plane of the radiation emitted from the plates

The light intensity at the output of the thermocouple 3, having m birefringent plates 5, recorded by the selective receiver 7, is equal to

(T) i0K sin2,

ON Oh

00

-N

but

OS

where lo is the light intensity at the input of the thermocouple 3;

K - coefficient taking into account the transmission of polarizers 4;

p d (t) is the phase shift between orthogonally polarized at the output of the birefringent plate 5;

d (T) is the thickness of the birefringent plate 5.

The thickness of the birefringent plate 5 is selected from the condition of matching the angular aperture of the light source (in this case, the optical fiber) with the angular distance between the isochromates, which has the form

1 (t)

I

Pmaks

(2sh)

where I is the source radiation wavelength;

Pmax is the maximum value of the refractive index of the material of the birefringent plate;

(l is the difference between the refractive indices of the material of the birefringent plate;

2 (a - radiation source aperture

The range of measured temperatures is determined by the temperature dependence of the refractive indices of the anisotropic material and its linear expansion coefficient.

Claims (1)

A device for measuring temperature comprising optically coupled monochromatic source a thermal converter and a selective receiver, the thermal converter being made in the form of a birefringent plate placed between two polarizers, the optical axis of which is at an angle of 45 ° with respect to the main direction of polarizers that are oriented orthogonally, characterized by measurement accuracy, the thermocouple is equipped with additional birefringent plates and polarizers by the number of these plates alternating with them, with the optical axis of each g additionally birefringent guide plate is oriented at an angle of 45 ° with respect to the main orthogonally oriented directions of the polarizers between which it is located, and the thickness of birefringent guides plates equals d - And Pmaks 0 / (202 where i is the wavelength of the source radiation; Pmax - the maximum value of the refractive index of the material of the plates; / and - the difference of the refractive indices of the material of the plates; 2 aperture of radiation source.