The paper presents the original method of calculating the speckle noise that appear in the light wave reflected from the electro optical medium that periodically modulates the wave. It has been shown that the problem is mathematically described by the Rice statistical model. The calculation of the noise component at processing the periodic electro optical modulation of the reflected light is implemented by means of the so called two parameter method of moments, namely-by processing the data for the second and the fourth moments of the signal to be measured. As a result both the useful signal and the noise dispersion are being jointly estimated. The estimation of the speckle noise value in the reflected periodically modulated light allows increasing the accuracy of the medium's electro optical coefficients' determination if compared with the traditional techniques. The dependence of the estimations' precision on the sample length has been studied.

Phase shift δϕ of the transmitted light flux is determined as the product of thickness l and birefringence δn(E) induced by the field E: δϕ = l·δn (E). To measure the EO effect, it is necessary to convert the phase EO shift of the optical flow into amplitude modulation. Such a transformation can be carried out by means of various interferometric schemes in which at least one of the interfering beams passes through the EO medium [1]. The most popular scheme of converting the phase EO shift into amplitude modulation is now the polarization optical scheme (POS) in which the polarized light passes through the EO medium [2]. In this scheme, with mutually perpendicular orientation of the axes of the analyzer and polarizer, the optimum orientation of the optical axis of the EO medium leads to amplitude modulation described by the following nonlinear equation:where I 0 is the intensity of the incident light and I is the transmitted light intensity and Δϕ-the difference of phase shifts, (Δϕ = 2πlδn/λ, λ-wavelength).In strongly absorbing media and in the films with low induced phase shift, the measured intensity change of the light which has passed through the POS may not be sufficient for reliable studies.Phase shift in EO media happens because of the fieldinduced refractive index change, i.e., because of so-called field-induced birefringence. This change causes a phase phenomenon for passing waves. Light waves of different orientations of their linear polarization with respect to the optical axis of the crystal (the ordinary and extraordinary wave polarization) experience different refractive indexes and get thereby different phase delays after passing EO media. This phase delay difference is converted into amplitude modulation by the output analyzer of POS.(2) I = I 0 sin 2 �ϕ 2Abstract This paper considers a method of estimating some parameters of electro-optic media by means of measuring electro-modulation reflection factor for ordinaryand extraordinary-polarized light. The results of measuring electro-optic coefficients of induced birefringence by applying alternating electric field to quartz crystals SiO 2 as well as to LiNbO 3 and PLZT ceramics are described.

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The design and operating of a portable holographic interferometer for residual stress analysis by creating a small scratch along with a new mathematical algorithm of calculations are discussed. Preliminary data of the stress investigations on aluminum and steel alloys have been obtained by the automatic processing of the interference pattern using a notebook computer. A phase-shift compensation technique in real-time reflection interferometry is used to measure the out-of-plane stress release surface displacement surrounding a small scratch (25 µm depth and 0.5 mm width) in a plate with residual stress of around 50 MPa. Comparison between theoretical models for a rectangular and triangular shaped scratch with the experimental data are presented.

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