13th International Conference on Fracture June 16–21, 2013, Beijing, China -3- where is the wavelength of a laser, α – the relation of diameter of the lighted area of a research surface to distance from a research surface to a point of registration of the speckle for objective speckle pattern; α – the relation of diameter of an entrance aperture to focal length of optical system for subjective speckle pattern. The dynamic processes arising on a surface of research object, lead to change of parameters speckle pattern (size and intensity) in space and in time that is connected with change of a phase of the reflected secondary spherical waves. Therefore, according to the analysis of existential behavior of the speckle pattern it is possible to investigate the dynamic and static processes of a research surface. 2.1. Proposed solution As it was noted, parameters of the speckle pattern, changing in space and in time, are: longitudinal and transversal sizes; distribution of the intensity. Let's estimate possibility of research of dynamic processes at the expense of measurement of parameters of the speckle pattern. From Eq. (1) and (2) follows that the sizes of the subjective speckle pattern don't depend on dynamics of a research surface as α is a constant, and are therefore connected only with characteristics of optical system. Thus, the subjective speckle pattern doesn’t allow to register displacements of a research surface, at the expense of measurement of the sizes speckle. On the other hand, registration subjective speckle pattern allows to tie rigidly its spatial arrangement in the image plane to a concrete point of a research surface. For registration of displacements in it cases are used methods of two expositions or averaging in time with the subsequent processing of interferograms. Let's carry out a similar assessment for the objective speckle pattern. At dynamic displacements of a research surface of change of the sizes of a speckle for objective speckle pattern according to Eq. (1) and (2) will be defined by the following ratios: D r r L 2 2 4 , (3) D r r H 1,22 , (4) where r – distance from a research surface to a point of registration of the speckle; ±Δr – the value of displacement of a research surface; D – diameter of the lighted area of a research surface. From the analysis of Eq. (1) and (2) follows that the transversal and longitudinal sizes of a speckle will change at very small value, as under real conditions of measurements Δr/r≈0. Therefore, as well as in a case with the subjective speckle pattern to define dynamics of a research surface at the expense of measurement of the sizes objective speckle pattern also it is almost impossible. Let's consider possibility of definition of dynamics of a research surface, at the expense of registration of change of intensity of the speckle. Change of intensity of a speckle occurs at the expense of change of its phase which depends on change of an optical way at displacement of a research surface. Change of value of a phase of the speckle on ±π (2n+1), (where n=0,1,2. …) leads to change of intensity of the speckle from the minimum value to maximum or on a turn. For registration of change of a phase of the speckle is necessary to use the reference beam of a laser radiation which is imposed on the speckle pattern, and therefore the secondary interference pattern in the form of fringe pattern is formed. Width of secondary interference fringes d is defined by well-known equation [8]:
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