PRECISE DETERMINATION OF THE CHOLESTERIC PITCH OF A CHIRAL LIQUID-CRYSTAL IN A CIRCULARLY ALIGNED CONFIGURATION

We propose a novel method of measuring the cholesteric pitch of a liqu id crystal (LC) in a circularly aligned configuration. The LC cell is made with one homogeneously rubbed surface and one circularly rubbed s urface so that it produces a disclination line passing through the sin gularity created by the circular rubbing. This disclination line is as sociated with two domains with different twist orientations. In such a geometry, the relationship between the angular deviation of the discl ination fine and the cholesteric pitch is analytically derived. The co ncept of a homogeneous-circular configuration is adopted to accurately measure the cholesteric pitch of LC in a broad range from 0.5 to 500 mu m. (C) 1997 American Institute of Physics.