A Study of Optical Uniformity of Lithium Niobate and Paratellurite Crystals by the Method of Conoscopy

An exact equation of the isochromatic fringes of uniaxial crystals derived without usually adopted simpli cations is presented. It enables to calculate the optical conoscopic gures for ideal crystals with di erent angular orientations of the optical axis with respect to the normal to the crystal surface. Conoscopic gures of large-size single crystals of lithium niobate and paratellurite were examined experimentally making use of a laser-based setup. The conoscopic gure evolution in operating acousto-optic devices was studied.