Optics: measuring and testing – Optical pyrometers
Patent
1977-05-05
1979-02-20
Corbin, John K.
Optics: measuring and testing
Optical pyrometers
73355R, 250474, 356 44, G01J 552, G01J 558
Patent
active
041403932
ABSTRACT:
This invention relates to the use of a birefringent crystal as the sensing element in a probe thermometer constructed of certain basic optical components utilized in three separate modes. Thus, all of the modes of the invention are directed to a probe thermometer which uses the temperature dependence of the birefringence of certain single crystals as the temperature sensitive parameter. One such crystal is a Y-cut single crystal of LiTaO.sub.3. Alternative crystals having adequate sensitivity in the desired temperature range may be constructed from LiNbO.sub.3 or BaTiO.sub.3. Polarized light propagates through the crystal in two modes, the ordinary ray and the extraordinary ray, which have indices of refraction n.sup.o and n.sup.e. For LiTaO.sub.3 at room temperature, n = 2.2, B = n.sup.e - n.sup.o = 0.004, and dB/dT = 4.4 .times. 10.sup.-5 /.degree. C. The intensity of light passed through a sandwich of aligned sheet polarizer, crystal, and optical analyzer is a function of B and hence also is temperature dependent. A thermometer probe is constructed by bonding this sandwich to a bundle of optical fibers along with a dielectric mirror so that the sensor will be at the probe tip. The probe has been constructed for use in the presence of intense electromagnetic fields and also designed to eliminate the possible hazard of an electrical leakage back to the subject.
REFERENCES:
patent: 3453434 (1969-07-01), Takami et al.
patent: 3675125 (1972-07-01), Jaecklin
Miller, et al., "Temperature Dependence of the Optical Properties of Ferrectric LiNbO.sub.3 & LiTaO.sub.3," Applied Physics Letters, Aug. 1966, pp. 169-171.
Bloem et al., "Immersible Fiber Optic Probe," IBM Tech. Disc. Bull., vol. 18, Jul. 1975, pp. 365-366.
Corbin John K.
Novack Martin
Punter Wm. H.
The United States of American as represented by the U.S. Governm
University of Arizona
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