Patent ID: 6757062
Filing Date: 2004-06-29
Classification: G01B

Abstract:
A method of measuring a thickness d of a liquid crystal layer having alignment-treated upper and lower surfaces and a birefringent index &Dgr;n which is uniform in the thickness direction, in a reflection-type liquid crystal display element including said liquid crystal layer between a pair of substrates and having a reflection region at least in a part of one of said substrates, comprising:a light-receiving step of entering light from a light source into said liquid crystal layer via a first polarizing means having a transmission axis and receiving, via a second polarizing means, reflected light exited from said liquid crystal layer by reflecting at said reflection region; a dispersing step of spectrally resolving the reflected light received by said light-receiving step to detect a relation between a wavelength &lgr; and a reflected light intensity; a wavelength deriving step of finding a wavelength satisfying a polarizing plane-maintaining condition in that said reflected light returns from said reflection region maintaining a same polarizing plane as a polarizing plane at the time of said light entering, in that a difference in optical path lengths between an ordinary ray and an extraordinary ray of said reflected light is a sum of an integer multiple of a wavelength and a half-wavelength, or an integer multiple of a wavelength; &Dgr;nÂ·d deriving step of finding a reasonable &Dgr;nÂ·d from the wavelength found by said wavelength deriving step and a known twist angle of said liquid crystal layer to find a relation between the wavelength and &Dgr;nÂ·d from a plurality of combinations of the wavelength and &Dgr;nÂ·d; and a thickness deriving step of finding the thickness d of the liquid crystal layer by assigning a known combination of wavelength &lgr; and &Dgr;n to the relation.