METHOD FOR MEASURING CELL THICKNESS OF LIQUID CRYSTAL CELL AND MEASURING APPARATUS USING THE SAME

摘要

PROBLEM TO BE SOLVED: To highly accurately measure a cell thickness of a liquid crystal cell including a twisted orientation liquid crystal by making it possible to apply the Senarmont principle to the measurement. SOLUTION: A light projected from a laser oscillator 11 is taken out as a linearly polarized light L0 with the use of a polarizing plate 4. The linearly polarized light is shed onto a liquid crystal cell 3 to be measured which includes a TN(twisted nematic) liquid crystal of a twist angle of 90 deg.. The light projected from the liquid crystal cell is input to a 1/4 wave length plate 6, and an azimuth angleθof a polarization axis L1 of the light out of the 1/4 wave length plate is detected. An apparent retardation R' is calculated from the azimuth angleθ. A true retardation R is converted from the apparent retardation R'. A thickness (d) of the cell is calculated from the true retardation (R=Δn.d:Δn is a difference of indices of refraction in a horizontal direction and a vertical direction of the liquid crystal).