I.N. Danilov - postgraduate student of Department of Physics and Optical System Technique, Nizhny Novgorod State Technical University n.a. R.E. Alekseev. E-mail: danilovnn@yandex.ru V.K. Maystrenko - Ph.D. (Eng.), Associate Professor of Department of Physics and Optical System Technique, Nizhny Novgorod State Technical University n.a. R.E. Alekseev. E-mail: vkmay63@gmail.com