535.423+617.7The basic principles and possibilities of optical coherence tomography (OCT) as a method for the investigation of pathologies in medical diagnostics are outlined. We discuss the OCT method limitations and issues related to the need for improving the resolution of optical tomographs. The prospects are considered for developing the OCT methods based on probing with diffraction-free light beams.

The detailed theoretical and experimental investigations of the self-reconstruction of the structure of Bessel beams in various scattering media, including biological tissue, have been carried out. Also the self-reconstruction of Bessel beam after shadowing with single obstacle is studied. Using conical beams, the peculiarities of speckle contrast imaging of subsurface targets embedded into highly scattering media have been investigated.

UDC 535.423The problem of reflection and refraction of a conical beam at the boundary of an object of cylindrical shape is solved analytically. The amplitude and energy coefficients of reflection for a field of variable polarization are calculated. The light energy absorption in a cylindrical object and its distribution over the cross section are investigated. The advantage of using conical beams of light for probing cylindrically shaped objects, including biological ones, is shown.

We have carried out the calculation and experimental measurement of the field formed by optical schemes composed of an axicon and lens with strong spherical aberrations. The calculation is performed by the methods of geometrical optics and diffraction integral. A mechanism is revealed, which is responsible for increasing the intensity in the near-axial focus of the doublet. It is shown that the formed bottle beam has a small length and the field at the periphery is of two types: oscillating and smooth ones. The changeover of the field from the bottle beam to a z-dependent Bessel beam is traced. The last beam is characterized, in particular, by the Bessel-type structure of its Fourier spectrum.

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