Home – Home – Jornals – Avtometriya 2008 number 6

Estimation of the regression model parameters is considered. A new approach to estimating the parameters for random error distributions that differ from the normal one and may be represented as the A-type Gramm-Charlier series is proposed. The developed approach is compared with the traditional least squares method and the sign method by means of computing experiments.

A new contrast image reconstruction algorithm is proposed. The algorithm is a combination of an iterative quadratic functional minimization algorithm and a local smoothing algorithm. A point-spread function of the iterative algorithm is introduced and a method for its calculation is proposed. The stopping time of the iterative algorithm is found from the required iterative algorithm resolution that is found using the point-spread function. The local filter makes it possible to reduce substantially the random error of image reconstruction without increasing the systematic error.

IR image defects (faults, overshoots, and a strong additive periodic noise) are analyzed for an autonomous observation system with an unstable radio channel communication.

Data on computer modeling a meniscus image of a crystal grown by the Czochralski method from a high-temperature melt are presented. A fine structure of the crystallization zone image formed by an optical projection system is investigated as well as the image components conditioned by intrinsic emission of the heater, melt, and crystal, and by emission reflections from melt and crystal surfaces. Causes of meniscus image parallax are analyzed; its influence on metrological characteristics of the optical crystal geometry control system is assessed.

Methods of laser interferometry based on the optical feedback and frequency-modulated laser diode effects are described. An interference signal is analyzed for problems concerned with range finding, displacement estimation, and measurement of velocities and vibration parameters. Relationships between the object movement characteristics and the interference signal parameters are found. Advantages of the new trend in interferometry are an extremely high sensitivity to scattered light, the possibility of estimating the displacement direction and obtaining information from small object surface areas, simple design, and low cost of the interferometers.

Results of investigating dynamics of a precision frequency divider by 3 based on a selfphase-locked doubly resonant optical parametric oscillator and triply resonant oscillator are described. It is shown that in the two cases, manifestations of self-phase locking are a dip of intensity and resonator eigenmode broadening.

A laser Doppler tomography method is proposed for investigating scattering noises, shrinkage, modulation amplitudes of refractive index and absorption coefficient, and other characteristics of volume or thick recording media. The method is based on acoustooptical scanning of a test volume grating recorded earlier in the medium and on layer-by-layer collinear heterodyne detection of the scattered field. The optoelectronic scheme of the system intended for experimental validation of the method is considered. Formulas for estimating the spatial resolution of the method, the optimal test grating period, the maximal number of detected layers are obtained. Their dependence on the optical system grating parameters is shown. An example is reconstructed values of the amplitude and phase of scattered light in deep layers of a volume grating written in a photopolymer 130 m thick.

Distortions of reconstructed data page images in a holographic memory under the Bragg deviation effect are experimentally investigated and modeled. It is found that not only the diffraction efficiency of the reconstructed image is reduced, but also the intensity distribution of information elements over the image field is nonuniform. For inhomogeneous volume holograms, distortions of the reconstructed data page image are more complex. As a result of blurring contour of the angular selectivity characteristic, the level of mutual interferences of neighboring holograms grows, but the intensity nonuniformity of information elements over the data page image field decreases.

A modified integer interferometry method is proposed for eliminating the interference fringe profile distortions caused by errors in interferogram recording and processing.

The profile is calculated for photogenerated nonequilibrium electron concentration in thickness of a three-layer film -MCT structure in crossed electric and magnetic fields, in which the band gap of the central region is constant, but increases in adjacent variband regions. It is shown that a three-layer structure with variband regions can be replaced by a homogeneous film via introducing effective surface generation and surface recombination velocities at boundaries of central and variband regions.

A gradient autonomous object movement control algorithm is proposed. The algorithm ensures search and tracing of a scalar field isoline for a vehicle with one sensor. A substantial limitation is the possibility of obtaining only local gradient estimates at discrete times. The algorithm is based on input of an additional test signal to the control system. This enables the vehicle with one sensor to calculate the total gradient value.

Principles of conversion of single time intervals into a digital code with the use of interpolation of the reference period for reducing the sampling error are reviewed. Interpolating converters are based on integrated digital delay lines and phase interpolation elements, which allow the resolution lower than the propagation delay of a single logical gate to be reached.