Abstract

This interferometric method has been devised for the simultaneous determination of the optic axis and thickness of a birefringent sample. It is analogous to the conventional microscope conoscopy, however it has the advantage of providing observations over a very large angle of incidence by using simple equipment. On the other hand, similar studies by usual methods would require expensive microscope objectives and condensors and a rather cumbersome image analysis method for quantitative measurements. Furthermore, the short working distance for a high numerical aperture objective prevents the insertion of any additional piece of equipment such as a heating stage needed for specialized studies. In this method the fringes of birefringence are obtained by scanning the field of observation. This has been achieved by successively varying the angle of incidence of the illuminating narrow beam of light. The fact that the zeroth fringe associated with the crystal optic axis is the widest, enables us to label unambiguously the orders of the fringes and to determine the fractional order with a high precision. The method has been dubbed as scanning conoscopy and has been used for accurate determination of Freedericksz transition and anchoring energies in nematic liquid crystals.

© 1986 Optical Society of America