This paper describes the theory of determination of small deformation tensor by means of the method, availing of statistical properties of the speckle field in an optically free space geometry or in a near image field. The small deformation tensor and a correlation function are briefly mentioned, and the main emphasis is aimed on theoretical derivation of the relationship between the correlation function of two speckle intensities, being recorded before and after deformation. This results in the relationship theoretically enabling a determination of all components of the small deformation tensor by means of a relatively simple optical arrangement in connection with computer and linear CCD detectors. Further, a compilation of all completed experimental results are briefly mentioned. An accuracy and sensitivity of this measurement methods are analyzed by theory of errors. As it flows from theory, the exact results at stress deformation, body displacement and rotation depend in crucially upon the geometrical arrangement of the optical system. The emphasis on the analysis of accuracy and sensitivity of individual geometrical parameters of assembly are given, with the aim to find an optimized geometry of experimental arrangement. The feasibility of an easy realization in practice and most importantly achieving satisfactory results of measurements are the important criteria. The conclusion presents some results obtained at concrete measurement with proposed experimental assembly.