A simple method for determining the pretilt angle of a vertically aligned reflective LCD

A field-induced birefringence method is demonstrated for determining the pretilt angle of a vertically aligned reflective liquid crystal display. We derive theoretically that the field-induced optical phase retardation is linearly proportional to the square of the applied voltage in the low-voltage regime. The pretilt angle can be deduced from the slope of this linear relation. The optical phase retardation is measured by a simple optical system and the pretilt angle can be determined easily. The experimental results agree well with that obtained theoretically. We also describe the applicable range of the applied voltage and the advantage of our method.