Richard L Haskell

US Patent:

54248434, Jun 13, 1995

Filed:

Dec 23, 1992

Appl. No.:

7/996321

Inventors:

Bruce J. Tromberg - Irvine CA
Tsong T. Tsay - Orange CA
Michael W. Berns - Trabuco Canyon CA
Lara O. Svaasand - Rudolf Raedersu, NO
Richard C. Haskell - Claremont CA

Assignee:

The Regents of the University of California - Oakland CA

International Classification:

G01N 2149
G01N 2159

US Classification:

356442

Abstract:

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 substances in the sample even though the sample is highly turbid.