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Title: Apparatus and method for qualitative and quantitative measurements of optical properties of turbid media using frequency-domain photon migration

Optical measurements of turbid media, that is media characterized by multiple light scattering, is provided through an apparatus and method for exposing a sample to a modulated laser beam. The light beam is modulated at a fundamental frequency and at a plurality of integer harmonics thereof. Modulated light is returned from the sample and preferentially detected at cross frequencies at frequencies slightly higher than the fundamental frequency and at integer harmonics of the same. The received radiance at the beat or cross frequencies is compared against a reference signal to provide a measure of the phase lag of the radiance and modulation ratio relative to a reference beam. The phase and modulation amplitude are then provided as a frequency spectrum by an array processor to which a computer applies a complete curve fit in the case of highly scattering samples or a linear curve fit below a predetermined frequency in the case of highly absorptive samples. The curve fit in any case is determined by the absorption and scattering coefficients together with a concentration of the active substance in the sample. Therefore, the curve fitting to the frequency spectrum can be used both for qualitative and quantitative analysis of substancesmore » in the sample even though the sample is highly turbid. 14 figs.« less
Inventors:
; ; ; ;
Issue Date:
OSTI Identifier:
63445
Assignee:
Univ. of California, Oakland, CA (United States) PTO; SCA: 440600; PA: EDB-95:092550; SN: 95001401173
Patent Number(s):
US 5,424,843/A/
Application Number:
PAN: 7-996,321; CNN: Contract N00014-91-C0134
Contract Number:
FG03-91ER61227
Resource Relation:
Other Information: PBD: 13 Jun 1995
Research Org:
University of California
Country of Publication:
United States
Language:
English
Subject:
44 INSTRUMENTATION, INCLUDING NUCLEAR AND PARTICLE DETECTORS; MEASURING INSTRUMENTS; DESIGN; SOLIDS; OPTICAL PROPERTIES; FLUIDS; LASER RADIATION; MEASURING METHODS; DATA PROCESSING; OPTICAL SYSTEMS; TURBIDITY

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