Spectrophotometric determination of reflective liquid crystal cell parameters

Abstract

We introduce a method for the determination of the optical retardation, its wavelength dispersion, the cell twist angle, and the orientation of the input director in a reflective liquid crystal (LC) cell. These parameters are found from the extremes of a characteristic function defined as a sum of two spectral reflectivities of the LC cell placed between a pair of linear polarizers. The reflectivities are measured for two cell orientations, one of which is arbitrary and the other one is turned through 45°. Both theoretical analysis and experimental procedures are presented. Excellent agreement between the experiment and our theory has been found. The proposed method can be applied to the measurement of reflective LC cells with small and large cell gaps, as well as cells with small and large twist angles.

Accurate color predictability based on a spectral retardance model of a twisted-nematic liquid-crystal display

“…Since this information is not always available in commercial displays, a number of reverse engineering experiments have been proposed in the literature to measure such parameters, prior to selecting the appropriate polarization configuration [4]. In order to avoid ambiguities in the solution of the parameter's values, these techniques involve measuring the transmission of the LCD in the off-state for various polarization configurations and for various wavelengths [5], or even taking spectral measurements [6][7][8]. The birefringence of the liquid crystal is wavelength dependent [9], and therefore, the optical modulation response of LC displays has a strong chromatic dispersion [10][11][12].…”

P‐70: Characterization of Liquid Crystal Material and Cell by means of Generalized Spectroscopic Ellipsometry

“…It is understandable that the reliability of simulation or optimization procedures depends critically on reliability of the parameter values used. Many methods for characterization of LC cells have been introduced [1][2][3][4][5][6][7][8][9][10][11][12][13][14], but none of them deals simultaneously with determining all parameters mentioned above. Majority of the values must be known a priori.…”

UV‐induced in‐plane anisotropy in layers of mixture of the azo‐dyes SD‐1/SDA‐2 characterized by spectroscopic ellipsometry

“…Moreover, such knowledge enables insight about the structure and physical properties of the material used. The thickness of the layer (10 -20 nm) is too small to be studied with one of the methods proposed earlier by us for LC cells [7][8][9]. However, the problem can be solved by applying spectroscopic ellipsometry.…”