Anatoly A. Chaussky

Refractive index matching of tissue components as a new technology for correlation and diffusing-photon spectroscopy and imaging

The refractive index matching of components of highly scattering tissue has a strong influence on its transmittance and reflectance what can be considered as a new tool for imaging within relatively thick tissues. We present experimental data on various solutions, gels and oils influence on optical properties of in vivo human eye and in vivo human skin. The dynamics of tissue optical properties depending on matter diffusion rate within tissue is studied. The possible application of refractive index matching effect for diffusing-photon imaging is discussed.

Dynamical and structural diagnostics of living tissues using speckle techniques

Basing on such fundamental optical phenomena as elastic and quasi-elastic light scattering, diffraction, and interference of optical fields we have designed coherent optical methods offering much promise for biomedical applications. The scope of research includes the development of photon-correlation spectroscopy, speckle-interferometry, coherent micro-topography of living tissues, and study of optical images contrasting due to reduction of scattering properties of surrounding medium using immersion liquids.

Tissue structure and blood microcirculation monitoring by speckle interferometry and full-field correlometry

In this paper a few speckle techniques is discussed from the point of view of their application for medical diagnosis in dermatology and ophthalmology using monitoring of tissue structure and blood microcirculation. The basic principles of proposed techniques and corresponding hard and software descriptions are presented. Results of model (tissue phantoms), in vitro and in vivo measurements for the human eye tissues and skin are discussed.

Interferometric testing of the random phase objects (biological tissue models) by spatially modulated laser beam

The diffraction of a laser beam with a spatial amplitude-phase modulation in the form of regular interference pattern behind random phase object as biological tissue model is studied. The interference effects of speckle-fields formed in diffraction zone are considered. The concept of interference of mutually shifted partially developed identical speckle fields has been employed. The evolution of visibility of average intensity fringes formed in scattered field has been studied for the objects with different statistical parameters modeling various cell structures including objects with an oscillating correlation coefficient of phase inhomogeneities. The behavior of the speckle field interference induced by the focused spatially-modulated laser beam diffraction on the random phase objects has been studied. A new measuring technique of statistical parameters of transparent or reflecting random phase objects is discussed. The technique is based on the usage of the probing beam with regular interference pattern, focused on a moving object, and on measurement of contrast of average intensity fringes, formed in scattering dynamic speckle-modulated field. Biomedical applications of the developed modeling and measuring technique are discussed.

Contrast of sine-wave fringes in imaging system with random phase screen in spatial-frequency plane

In optical system with double Fourier-transformation and with an illuminating spatially modulated laser beam, scatterer in an entrance plane and a random phase object in spatial-frequency plane the process of formation of average intensity interference fringes in the plane of the image is considered. It was shown that the optical system can work in shift interferometer mode. The analytical expressions for the contrast of the image of fringes as functions of objects statistical parameters and parameters of an illuminating beam (fringe spatial frequency and beam aperture) are obtained. It is established that in coherent and incoherent optical systems with scatterer in an entrance plane the contrast of the image of sine-wave fringes depends similarly on parameters of object in spatial-frequency plane and parameters of optical system.

Optical testing of the random phase objects using spatially modulated laser beam

A new measuring technique of statistical parameters of transparent or reflecting random phase objects including biological tissue is discussed. The technique is based on the usage of the probing spatially modulated laser beam (beam with regular interference pattern), focused on a moving object, and on measurement of contrast of average intensity fringes, formed in scattered dynamic speckle- modulated field. The behavior of the speckle field interference induced by the focused spatially modulated laser beam diffraction on the random phase objects has been studied. The dependence of dynamic field average intensity fringes contrast on the statistical properties of moving object has been established both experimentally and theoretically.

Laser interferometry of random phase objects

In the present paper physical bases of a new direction in interferometry - laser interferometry of random inhomogeneous objects, within the framework of which in difference from classical interference methods as a measuring signal not the form of interference fringes or dynamics of their change, and contrast of fringes carrying the information o statistical parameters of object are considered. The interference of identical and non-identical partially developed speckle-fields is studied. The dependencies of contrast of mean-intensity holographic interferometers. The possibility of using spatially modulated laser beam to determine statistical parameters of scattering objects, namely, the phase variance, the correlation length, and the form of the coefficient of correlation of optical inhomogeneities, is considered.

Light interference in the diffraction field of a spatially modulated laser beam behind a random phase object

The diffraction of a laser beam with spatial amplitude-phase modulation in the form of a regular interference pattern behind a random phase object is studied. The interference effects of correlation of speckle-fields formed in the zone of diffraction are considered. To physically interpret the observed effects, there has been employed the concept of interference of mutually shifted partially developed identical speckle fields. The evolution of visibility of average intensity fringes formed in the scattered field has been studied for the objects with different statistical parameters including objects with an oscillating correlation coefficient of phase inhomogeneities. The correlation properties of formed partially developed speckle fields are considered for an illuminating Gaussian beam with an account of the observed interference effects. It has been shown that under certain conditions the form of variation of the fringe visibility coincides with the form of the correlation coefficient of the complex amplitude of the boundary field (the field in the plane, located in the immediate vicinity to the object plane) and, hence, is uniquely defined by inhomogeneities parameters of the object: by standard deviation, correlation radius and correlation coefficient form. The application possibilities of the considered processes for diagnostics of phase scattering objects complying with the model of a random phase screen are discussed.