Abstract

The optical properties of scattering media determine the attenuation (A) and the transit time (〈t〉) of light reflected from the medium as well as the phase (Φ) and modulation depth (M) of an intensity-modulated lightwave. Our primary finding is that the ratio of changes in A, Φ, and M is approximately independent of the scattering properties and gives a good estimate of the absorption coefficient. These changes can be induced either by small changes in the absorption coefficient of the medium, by the tuning of the wavelength, or by changes in the light source–detector distance. The application for the in vivo monitoring of hemoglobin and oxyhemoglobin concentrations in human tissue is discussed.

© 1997 Optical Society of America

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