NOVELTY - The method involves measuring light intensities transmitted by a liquid crystal display; calculating liquid crystal display Stokes parameters based upon the intensities of the measured transmitted light and determining the thickness of a liquid crystal cell and a twist angle of liquid crystal molecules based upon the liquid crystal display Stokes parameters.    USE - For measuring the thickness of a liquid crystal layer and the twist angle of liquid crystal molecules within the liquid crystal layer of an LCD.    ADVANTAGE - Measurements of an entire display can be performed quickly and with high accuracy, by avoiding extinction measurement methods requiring some complicated rotation operations of the liquid crystal cell or polarizers for determining the angles of maximum and minimum transmissions, and by avoiding the problem where cell thickness and twist angle is measured at only one probing point, where thus in order to map a two-dimensional cell, the LCD must be mechanically moved from point to point.    DETAILED DESCRIPTION - The step of measuring the transmitted light intensities includes the steps of: interposing a polarizing plate between the liquid crystal display and a photodetector in a direction of an X axis and measuring a transmitted light output Ix using the photodetector; interposing a polarizing plate between the liquid crystal display and a photodetector in a direction of a Y axis and measuring a transmitted light output, Iy, using the photodetector; and interposing a polarizing plate between the liquid crystal display and a photodetector in a direction of 45 degrees between the X and Y axes and measuring a transmitted light output I45 using the photodetector. The step of calculating liquid crystal display Stokes parameters according to the measured transmitted light intensities from the liquid crystal display is determined by the Stokes parameters S0, S1, and S2 according to the following equations: S0=(Ix+Iy)/(Ix+Iy)=1, S1=(Ix-Iy)/(Ix+Iy), and S3=(2(I45)-(Ix+Iy)/(Ix+Iy). An INDEPENDENT CLAIM is included for a device for determining liquid crystal display parameters.    DESCRIPTION OF DRAWING(S) - The drawing shows a block diagram of the measurement method.    light source, e.g. HeNe laser (1)    polarizing plate acting as polarizer (2)    liquid crystal display (3)    polarizing plate acting as analyzer (4)    quarter wavelength plate (5)    photodetector (6)    processor (7)