Three-dimensional transient finite difference numerical model of the biological tissue irradiated by powerful laser beam is developed. It is used to simulate the thermal behavior of tissue assuming that radiation wavelength is chosen to give rise for volumetric heat sources. A three-dimensional seven-flow model is used to calculate radiation propagation. Evaporation and burn-out of tissue resulting in a through hole along the axis of the beam are taken into account. Besides the water boiling and corresponding changes of thermal and optical tissue properties the model takes into account one of the heat steam transfer mechanisms. Estimates are carried out for the effects of diffusion transfer and vaporization of water from the tissue surface. Kinetics of protein denaturation process are calculated by Arrenius equation. The problem is solved numerically using discrete grid technique and adaptive time-step control algorithm.

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Optical images of 'laser radiation. passed through a tissue of the rabbit (abdominal front wall and ear) in vivo. and passed through a model medium -various thickness fluoroplastic disks have been received. New projection method of medical image processing based on signal expansion into series of eigenfunctions of the Fourier transform has been applied. The comparative analysis of results allowed detecting structural feathres of patterns of laser emission scattering by tissue.

The degree of depolarization of laser light scattered from an isotropic rough silicon surface and a unidirectional rough steel surface was measured with apolarometer inthe specular direction for angles of incidence from 300 to 800.Rms roughness of the surfaces was greater than laser light wavelength and less than correlation length of the roughness. For the laser light linearly polarized at a 45 angle to the plane of incidence, dependence of the measured degree of depolarization on angle of incidence has one maximum and angle of incidence corresponding to the maxima is closett-thepseudo-&ewster angle for a smooth surfaceior both the silicon and the steel. It is found experimentally that the reason for the measured depolarization is spatial variations of the azimuth and the ellipticity of the fully polarized scattered light withiira: polarometer aperture Computer simulation of the scattenng from a one-dimensional rough steel surface satisfactorily describing the dependence of the measured degree of depolarization on angle of incidence for the unidirectional rough steel surface for angles oflncidence up ta 70° inclusive shows the single scattering niake the main contribution to thei1endence ofthe measured degree ofdepolarizatian on angle of incidence.