To test different models of HTSC and to study mechanism of this phenomenon comparison of themeasured complex dielectric function e(w, T) and of the computed one is very useful. In the case ofanisotropic substance, such as Y Ba2Cu307, e(w, T) is tenzor with different ca, cb, ec components. However,the structure of oriented YBaCuO films permits to determine ec and only averaged cab value. To carryout ellipsometric measurements on small samples in far IR the light beam should be focused onto thesample surface. Earlier we find an original decision of the direct problem of convergent beam ellipsometryl(CBE). This report is devoted to the inverse problem of CBE for the following reflecting system: 1-axisanisotropic film on isotropic substrate. By this technique we have obtained temperature dependencies (4Ã¢â‚¬â€ 300 K) of Cab and c, at fixed laser frequencies 84, 120, 357 cm-1.