Simultaneous measurement of twist angle and cell gap of a twisted nematic cell by an optical method

An optical method is presented which makes it possible to measure simultaneously the twist angle and the cell gap of a filled twisted nematic liquid crystal display that has an arbitrary unknown twist angle between 0 degrees and 360 degrees . It can also determine the sense of handedness of the twist and the two rubbing directions of an unknown panel. Using this method, the measurement uncertainty of the cell gap is within 1% and measurement uncertainties of the twist angle and rubbing directions are within 1 degrees .<>