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The origin and development of buoyant jets over a sudden linear heat source in a highly viscous fluid with a Prandtl number equal to 2700 are experimentally and numerically studied. The time evolutions of the spatial flow form and temperature and velocity fields are investigated as functions of power supply.

The results of recording gas flow in a shock tube by the schlieren and background oriented schlieren (BOS) methods after initiating a pulsed (surface or volume) discharge are presented. Simultaneous recording of the flow field by the two methods allows a complete qualitative and quantitative analysis of the shock-wave processes resulting from the interaction of a pulse discharge with high-velocity flow. The vector displacement field of the BOS method was determined by the cross-correlation method. The density field was obtained by solving the Poisson equation with special boundary conditions. It was shown that the BOS method yields a good quality map of the flow structure that corresponds to the classical schlieren method and provides reliable quantitative results except in areas of high gradients. A modification of the BOS method was proposed and tested to measure the density jump at the shock-wave front. Recording was performed at an angle to the plane of the wave front. Various Schemes of processing of digital flow images were tested. The proposed method provides a resolution of large density gradients at the shock-wave front. The obtained quantitative results are consistent with the calculated values.

Flows in horizontal fluid layers with a free upper boundary with uniform heating from below are studied. With the use of thermal imaging scanning, the temperature fields on the free fluid surface in laminar and turbulent regimes of the Rayleigh-Benard convection are measured. Computer processing of thermal imaging movies makes it possible to obtain spatial-temporal characteristics of cellular and multiscale convective flows.

The possibility of simultaneous measurements of the distance and velocity of diffusely scattering objects by active laser interferometry with frequency modulation is theoretically shown and experimentally substantiated.

A new version of the method of direct multibeam laser writing of diffractive optical elements (DOE) is proposed and investigated. A writing area in the form of an array of focused light spots is formed by splitting the writing laser beam into multiple beams by using a Dammann grating and focusing of these beams in the plane of a moving carrier with a photosensitive material. Adjustment of the radial pitch of writing and correction of the uniformity of the beam intensity is carried out by tilting the Dammann grating and displacing it in the dispersion direction. In writing DOEs, the radial pitch of discrete displacement of the writing area with respect to the plane of the DOE is set equal to or multiple of the average radial distance between the radial projections of the centers of the focused light spots. This version provides improved performance and accuracy due to high-quality paralleling of the writing beam and the averaging effect in superimposed writing.

The quality of the image formed by a MIOL-Akkord bifocal intraocular lens (diffractiverefractive lens) implanted into various known eye models is studied analytically. As the pupil radius increases, the Strehl ratio characterizing the resolution is demonstrated to decrease appreciably (down to 0.05-0.09) for models where the absolute value of asphericity of the frontal surface of the cornea is smaller than or equal to 0.26 (far vision) and 0.18 (near vision). The effect of the aspherical shape of the rear surface of the cornea on the image quality is considered. It is noted that the best results for both far and near vision are provided by the model with Lotmar's cornea for which the diffractive component of the MIOL-Akkord eye lens is calculated.

The configuration of a two-beam interferometer with fixed inclined mirrors for recording holographic gratings is described. The convergence angle of the partial beams is adjusted in the range from 0 to 180º by changing the angle of incidence of the primary beam on the entry edge of the beam-splitting cube without additional adjustment of the mirrors. The path lengths of the interfering beams are automatically aligned by the mirror symmetry of the system. The optimal kinematics of adjusting the convergence angle is found that allows working with beams of sufficiently large diameter in the whole range of adjustment. The interferometer is highly resistive to vibration due to lack of adjustment devices.

A 3D image in the form of a linear combination of two two-dimensional images located at different depths along the line of vision of the eye is considered. The loss of contrast and nonlinearity of accommodation over the depth with a high resolution acuity of 3D images are demonstrated in computer experiments with different eye models.

Numerical simulation was used to demonstrate the possibility of designing a two-mirror multibeam reflective diffraction interferometer using a single-mode fiber with a cladding. The method is based on the calculation of the multimode and multibeam interference of the cladding modes in the fiber describing the diffraction on a diffuser made in the form of an insert of a different fiber as part of one of the interferometer mirrors. It is shown based on bulk optics that using certain optimization, one can obtain a reflection-response function profile of this interferometer similar to that of the transmission-response function of a Fabry-Perot interferometer.

The dependence of the diffraction efficiency of polarization holographic gratings on the temperature of their formation is presented. The temperature range corresponding to the maximum diffraction efficiency of such gratings is determined. The possibility of thermo-optical switching of recorded gratings is demonstrated.