As stated in the previous section, commercial spectrophotome-ters are not suitable for the characterization of complex transparentsystems, because of geometrical and constructive limitations. For these reasons accurate measurements are not possible for samples characterized by complex geometry, high thickness or bulk scat-tering properties. A large diameter integrating sphere apparatus isneeded to perform accurate measurements on such materials [14]. The schemes in Fig. 2 show the system configuration of the optical facility used for the characterization of the PC samples described