ACCURATE MEASUREMENT OF THE PRETILT ANGLE IN A LIQUID-CRYSTAL CELL BYAN IMPROVED CRYSTAL ROTATION METHOD

To measure the pretilt angle in a liquid crystal cell, the crystal rot ation method is commonly used because it is very precise and the measu rement time is short. However, if the cell gap is not uniform, a signi ficant error occurs due to a shift of the measurement point. This shif t is caused by refraction at the glass plate when rotating the cell. I n this paper, we estimate the magnitude of this error theoretically an d experimentally and propose an improvement of the crystal rotation me thod by which an accurate value of the pretilt can be obtained even wh en the cell gap is not uniform.