Radiant energy – Photocells; circuits and apparatus – Optical or pre-photocell system
Patent
1989-08-01
1990-08-14
Nelms, David C.
Radiant energy
Photocells; circuits and apparatus
Optical or pre-photocell system
2502311, 374121, 374127, 374137, 356349, 356 43, G01N 1506, G01J 500, G01B 902
Patent
active
049489585
ABSTRACT:
To remotely measure the unknown subsurface temperature T.sub.s of a bulk transparent medium such as ocean water, a high intensity pulsed laser beam is split into two sub-beams, a probe beam and a reference beam. The probe beam is directed into a sample of ocean water of unknown temperature, and the reference beam into a reference sample of water having a known temperature T.sub.r. The irradiance of the two pulse beams exceeds a predetermined threshold sufficient to cause stimulated Brillouin scattering (SBS) within the two samples and produce therefrom two return phase-conjugate (PC) beams. A photodetector mixes the two PC beams and produces a heterodyne frequency that is proportional to the difference in temperatures T.sub.s and T.sub.r. A frequency measuring instrument converts the heterodyne frequency into a temperature value equal to T.sub.s.
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Hirschberg et al., "Speed of Sound and Temperature in the Ocean by Brillouin Scattering", Applied Optics vol. 23, No. 15, 8/84, pp. 2624-2628.
Gilbert Douglas M.
GTE Government Systems Corporation
Lawler John F.
Messinger Michael
Nelms David C.
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