It is known that the most widely used method to control internal strains is the optical polarization method. However, the sources of polarized radiation are the most problem issue of this method. There are some difficulties in using this method when testing large-scale optical parts, diameters of which exceed 500 mm. To choose an optical source suitable for solving these tasks, we have analyzed the design of liquid-crystal screens and ascertained the possibility to use their polarized radiation in tests of internal strains in optical parts of large dimensions. Adduced below are the results of investigations of internal strains in parts of sapphire and organic glass.

Fig.1 Internal strains in the bottom part of the sapphire single crystal.

Fig. 2. Internal strains in the bottom part of the sapphire single crystal.