Optics: measuring and testing – By polarized light examination – With birefringent element
Patent
1982-06-08
1984-05-08
Sikes, William L.
Optics: measuring and testing
By polarized light examination
With birefringent element
G01B 902
Patent
active
044471530
ABSTRACT:
An apparatus and method for the measurement of small differences in optical absorptivity of weakly absorbing solutions using differential interferometry and the thermooptic effect has been developed. Two sample cells are placed in each arm of an interferometer and are traversed by colinear probe and heating laser beams. The interrogation probe beams are recombined forming a fringe pattern, the intensity of which can be related to changes in optical pathlength of these laser beams through the cells. This in turn can be related to small differences in optical absorptivity which results in different amounts of sample heating when the heating laser beams are turned on, by the fact that the index of refraction of a liquid is temperature dependent. A critical feature of this invention is the stabilization of the optical path of the probe beams against drift. Background (solvent) absorption can then be suppressed by a factor of approximately 400. Solute absorptivities of about 10.sup.-5 cm.sup.-1 can then be determined in the presence of background absorptions in excess of 10.sup.-3 cm.sup.-1. In addition, the smallest absorption measured with the instant apparatus and method is about 5.times. 10.sup.-6 cm.sup.-1.
REFERENCES:
patent: 4229105 (1980-10-01), Silverbage
Cremers et al., "Optical Nulling for Trace Analysis Based on the Thermooptic Effect and an Interferometer", Abstract THMII in the Technical Digest of the CLEO '81 Conference on Lasers and Electro-Optics, Washington, D.C., Jun. 10-12, 1981, Digest date unknown.
Cremers et al., "Thermooptic-Based Differential Measurements of Weak Solute Absorptions with an Interferometer", Applied Optics, vol. 21, No. 9, pp. 1654-1662, May 1982.
Cremers et al., "Quantitative Measurement of Solute Absorption at Levels Below Solvent Absorption by Optical Nulling Techniques", Abstract A305 in Advance Program of the Los Alamos Scientific Laboratory Conference on Optics '81, Los Alamos and Santa Fe, N.M., Apr. 7-10, 1981, date of advance program unknown.
Stone, "Measurements of the Absorption of Light in Low-Loss Liquids", J. Opt. Soc. Am., vol. 62, No. 3, pp. 327-333, Mar. 1972.
Cremers David A.
Keller Richard A.
Esposito Michael F.
Freund Samuel M.
Gaetjens Paul D.
Koren Matthew W.
Sikes William L.
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