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Temperature Measuring Probe

IP.com Disclosure Number: IPCOM000052200D
Original Publication Date: 1981-May-01
Included in the Prior Art Database: 2005-Feb-11
Document File: 2 page(s) / 31K

Publishing Venue

IBM

Related People

Hinkel, H: AUTHOR [+4]

Abstract

This probe uses the temperature-dependence of the birefringence index o a suitable substance to measure the temperature of a surrounding agent. This is done by measuring the phase difference between the ordinary and extraordinary light beams reflected from the substance.

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Temperature Measuring Probe

This probe uses the temperature-dependence of the birefringence index o a suitable substance to measure the temperature of a surrounding agent. This is done by measuring the phase difference between the ordinary and extraordinary light beams reflected from the substance.

In the figure, a birefringent crystal, such as calcite, is surrounded by a cover of good thermal conductivity, which is used to measure the temperature of a surrounding agent. The crystal is illuminated by laser beam B3. When entering the crystal through window W, the beam is split into a non-deflected ordinary beam B1 and an extraordinary beam B2 which is deflected through an angle defined by the birefringence index of the crystal. At mirror M1, each beam is reflected back onto itself. Both beams leave the crystal through window W, and part of the reflected beam is deflected by mirror M2. Their different optical path lengths lead to a phase difference between beams B2 and B2. This difference is measured by the phase measuring device PMD receiving light beam B4. As the length of the optical path of each light beam depends on the corresponding index of the crystal and this index is temperature-dependent, the measured phase difference indicates the temperature o the crystal and the surrounding agent. Three effects contribute to an excellent measuring sensitivity of better than 0.01 degree C: the temperature-dependence of the birefringence, of the split angle and of the l...