Development of methods of light utilization enhancement in LCD backlight systems is an urgent task. Besides of usual approaches the light polarization management by diffractive optical elements (DOE) allows formation of beams with different polarization status (e.g., both linear and circular or elliptical). A software OAGSM developed earlier provides calculation of diffraction efficiency for optically anisotropic gratings with periodical surface microrelief. In this paper the software has been checked for the cases of oblique incidence as well as of microrelief variable squeezness and period. The results can be used for designing new efficient backlights. An example of the calculations made is an evaluation of the influence of parameter L-1/Lambda on the diffraction efficiency of the transmitted TE-wave for the normal incidence that is shown in Fig.l. The biggest value of the 1st order intensity as well as the lowest value of the zero order intensity is at L-1/Lambda=0.5. The 2nd order intensity dependence has two maxima and a minimum between them at L-1/Lambda=0.5.