Providing the temperature stability of the compensator parameters in the ellipsometer

In modern ellipsometers, the compensator is often a plate of a uniaxial crystal with the optical axis lying in the plate plane. The temperature variations of the ellipsometry data are due to the large thickness of the compensator used. A double compensator is proposed,consisting of two uniaxial crystal plates, with optical axes lying in the plate plane and being mutually perpendicular. It is shown that using as a compensator the uniaxial crystal plate with the optical axis making a relatively small angle θ with the plate normal, one can radically change the situation in ellipsometry by reducing essentially experimental errors due to temperature variations.