Optoacoustic measurement of optical properties of turbid media

摘要

Time-resolved laser optoacoustic method was developed for the measurement of the spatial distribution of laser fluence rate in uniformly absorbing and scattering condensed turbid media and to determine the optical properties of such media - effective light attenuation and absorption coefficients. This method is based on detection of laser-induced acoustic transients in an investigated medium with high temporal resolution. The effective light attenuation coefficient is measured by exponential fitting of the front of optoacoustic transient. To determine the light absorption coefficient we investigated features of the spatial distribution of laser fluence rate beneath the surface of an irradiated medium. We proved both experimentally and with Monte-Carlo simulation, that the location of the maximum of laser fluence rate distribution in a turbid medium depends solely on the ratio of light absorption and effective light attenuation coefficients, if the anisotropy factor of light scattering is higher than 0.8. This dependence can be employed to calculate the light absorption coefficient of turbid media from the leading edge of laser-excited optoacoustic transients.