Simple technique for determining the extraordinary axis direction for twisted-nematic liquid crystal spatial light modulators

We report a simple technique for determining the orientation of the extraor dinary axis at the input side of a twisted-nematic liquid crystal spatial l ight modulator. In this approach, we illuminate the display with linearly p olarized light and examine the diffraction pattern as we change the externa l Voltage applied to the display. When the incident light is polarized alon g the extraordinary axis, we see changes in the diffraction pattern as a fu nction of applied voltage. Experimental measurements and theory are present ed. (C) 1999 Society of Photo-Optical Instrumentation Engineers. [S0091-328 6(99)02005-X].