Commercial twisted nematic liquid-crystal television provides coupled
phase and amplitude modulation. We propose a simple wedged shear plate
interferometer for in situ measurement of its phase modulation and op
erating curve. For a given operating curve, the coupled-mode modulatio
n holograms are designed with an iterative method. We adjust the opera
ting curve by rotating the polarizer and analyzer to obtain the optima
l operating curve. The phase-mostly holograms yield good-quality recon
structed images with the zero-order spot reduced to a minimum. Experim
ental results are shown.