Nickolay N. Evtikhiev

Invariant correlation filter with linear phase coefficient holographic realization in 4-F correlator

Realization of distortion invariant correlation filters in optical image correlators open possibilities for object identification with remarkably high computational capabilities. Application of the linear phase coefficient composite filter (LPCCF) is attractive for recognition of binary edged images. We use methods of digital holographic synthesis to realize LPCCF in a coherent 4-F correlator as a computer-generated amplitude holographic filter. A high resolution spatial light modulator (SLM) has to be implemented for such a filter representation. Transparency limitations of high frame rate and high resolution SLMs and its effect on recognition performance of holographic filter in the 4-F correlator are discussed in the given paper.

Composite holographic screens for the stereoscopic or multiview color image display

The transmission type holographic screen is a special kind of scatterer, which is used to concentrate the light from the projected image into small size spot (viewing zone). As a result, different images can be delivered to each observers eyes and it is possible to display the stereoscopic images. The most serious problem related with the holographic screen is its high dispersion and aberrations which cause the viewing zone distortions and poor color reproduction in the displayed image, especially in the screen corners. Both of the above mentioned drawbacks become more prominent when the screen size becomes larger. To compensate the screen dispersion, a diffuser in the form of a long narrow stripe directed to the reference beam axis is used for an object. The length and position of the diffuser are calculated to make the reconstructed images of it for all wavelengths of the white light projector to be superposed in the viewing zone. To solve the aberrations problem, a big size screen was composed by mosaicking many sub-screens which were recorded individually in the specially optimized setup. For example, when the sub- screen is recorded for the edge part of the screen, the diffuser was tilted different direction to provide proper superposition of the reconstructed diffuser images. For each sub-screen, the diffuser is tilted such that it is in nearly the same plane with the reference beam axis. The sub-screens are recorded on the holographic photoplates PFG-01 (Russia) with an optical set-up optimized for each sub-screen by adjusting the diffuser position and its tilt angle. All necessary parameters are calculated by considering the light beam path for different wavelengths in the visible spectrum. The size of each sub-screen is 40 X 30 cm2. Eight sub- screens are mosaicked to obtain a composite holographic screen with size 80 X 120 cm2. The screens have been used to display the full color stereoscopic images from slide projectors. The distances between the projector and the composite screen, and the screen and a viewer are set to 4 m and 3.5 m, respectively.

New wavelet basis kernel filters (WBKF) based image recognition

One of the main problems of optical data processing is the problem of image recognition. There were given much attention to optoelectronic methods of recognition of distorted images nowadays. There are a number of different approaches for the solution of such problem. One of the most popular approaches is using of optical correlators for this field. The main problem of this approach is to select an object to provide a correlation of input image with it. One of the widespread methods is to use an effective object-an invariant correlation filter. The paper presents the results of investigations on image recognition with the help of Wavelet Basis Kernel Filters (WBKF). Both results of the theory and computer simulations are presented. Also computer simulations hold a comparison of image recognition results with the help of other different approaches (GMACE, SDF and so on). The obtained results seem to be better for WBKF recognition in some cases. There are presented authors suggestions about using of WBKF filters for different distortion invariant image recognition problems and results of image recognition in presence of white noise.

Invariant correlation filter design in problems of image recognition

Authors made a research in computer modeling of invariant correltaion filters design. The results of modeling shows good perspective of such approach for solution of image recognition problems. The aim of research is to find a type of filters that gives a stability of correlation peak for different geometrical distortions.

New filters for optical correlators

Authors made theoretical research in building of correlation filters, using direct decomposition of integral transforms on correspondent orthonormal basis. The obtained filters have different properties, which are quite good for different image recognition problems: 1). Such filters itself have all properties of elementary function; 2). From the family of such filters we can easily make MACE filters (authors made it for the case of wavelet transform); 3). Invariant properties of filters of this family are determined by the presence of such properties in integral transform, which is the base for construction of such filters (so we can select these properties by the selection of the type of transform). Also authors made experimental check-up of modeling of results on a computer. Results of modeling shows good perspective of such filters in solving of such problems.

Electroholographic display with minimum data redundancy

A method for synthesis of driving RF signal, corresponding to sampled hologram, which allows to minimize the capacity of the display memory, is suggested. With the application of new method required frame-buffer capacity for the current displays can be reduced by the factor 1.8 - 3. We have considered three variants of hologram sampling method for data reduction. It is found that minimum hologram data redundancy can be achieved with Fourier and Image types of holographic stereograms. For given 3-D image resolution a maximum image size, which can be displayed without redundancy is determined as 4...5 cm. Further scaling of the image requires application of the sampling method. With proper improvement of the hardware, application of hologram sampling method provides stable capacity of the display memory a little over 32 MB regardless of the image size. Since the method also permits direct synthesis of driving RF signal, acousto-optical modulators with up to several GHz bandwidth can be employed in electroholographic display.

Active laser system for sea ice control

The airborne systems are used for complex investigations of coastline very successfully, for example it can be used to measure the depth of the sea, to discover the reefs and so on. Such information may be used in navigation too. The specific conditions of navigation in the North and Pole seas defines the necessity of exact knowledge about the ice cracks in order to find the possible direction of the ship movement. The active optical system, working in the near IR region, has many advantages before the passive one, especially if it is necessary to work during the polar night and at bad weather conditions. In this article we discuss the demands to the laser active airborne systems, that given the accurate picture of the ice with high resolution in the daytime and nighttime conditions. Such system based on the laser, mechanical scanner and avalanche photodiode is very compact, reliable and informative. The picture of the ice surface can be shown on the TV monitor, can be written to the memory and can be delivered to the processing center by the radiochannel. The experimental results are shown together with results of this system probing in the conditions of the North Pole Ocean.

Two-cascade acousto-optic matrix processor for SAR systems

Recent years were marked by persistent attempts to create a hybrid optoelectronic matrix processor realizing matrix- vector multiplication and having greater throughput than its modern and perspective electronic analogues. An experimental breadboard model of such processor based on the multichannel acoustooptic modulator intended for processing of radar signals is described, results of mathematical simulation and experimental investigations are presented.

Hybrid hierarchical neural optoelectronic processor based on the vector-matrix multiplier and the preprocessing unit

Hierarchical hybrid neural optoelectronic system for pattern recognition based on moments invariant method is considered. The results of such system simulation are presented.

Optoelectronic processor for radar imaging based on the multichannel acousto-optical modulator

Recent years were marked by persistent attempts to create a hybrid optoelectronic matrix processor realizing matrix-vector multiplication and having greater throughput than its modern and perspective electronic analogues. An experimental breadboard model of such a processor based on the multichannel acousto-optical modulator intended for processing of radar signals is described, results of mathematical simulation and experimental investigations are presented.