The development of a technique is connected to the working out of new more exact methods of calculation of construction strength. The basis of such calculation is the analysis of the stress-strain state of the investigated object. The role of experimental methods in this process is invariably high. This experiment is applied not only to check out numerical or analytical investigations but it is also independent, and a unique approach to the solution of most complex strength problems. Necessity of experimental valuation of results which basically depend on choice of the account scheme and division of the research object into elements has increased in connection with wide application of numerical methods of stress-strain account (MFE, MFD, MBE). The phenomenon of photoelasticity which is peculiar in greater or in a smaller degree to all transparent materials is used in polarized- optical investigations at modeling of a wide circle of the experimental mechanics problems. The appearance of gas lasers as the sources of monochromatic polarized light has become the reason of further development of a polarized- optical method based on measurements of scattered light intensities (SLI) -- scattered-light method. Scattered-light method is the most perspective but poorly developed among the polarized-optical approaches of the stress-strain analysis. The practical application of the given method is constrained because of several objective reasons: (1) complexity and insufficient accuracy of approaches of characteristic parameters determination of the photoelastic model; (2) complexity of stress-optic dependencies connecting optical characteristics with stress in common cases of investigated objects loading; (3) absence of reliable approaches of stress division in three-dimensional problems of photomechanics. Therefore, the development and practical application of a scattered-light method used in solving three-dimensional problems of strained body mechanics is an important problem.