New method of designing LCD with optimal optical properties

Mueller calculus is employed to find the conditions that govern linear polarization preservation and the linear to circular polarization transformation in a general twisted nematic LC cell. The results are applied to the design of both transmittive and reflective twisted nematic LCDs. New optimized optical modes are reported. This method provides a clear physical interpretation of all LCD modes. Introduction We have previously introduced the 2Dparameter space for the optical design of general twisted nematic LCDs based on the 2x2 Jones matrix. Here we introduce another approach based on the 4x4 Mueller matrix for optimizing the optical properties of LCDs. This method has the advantage that polarization change of the light after passing through the twisted nematic layer can be seen very clearly. A parameter space can be generated which shows the relationship between all LCD modes, published and unpublished. We applied this new parameter space to the design of optical display modes including HTN, STN, RTN and RSTN etc. It is discovered that many of the announced display modes are indeed not optimized and can be further improved. Theory The Mueller matrix representation of a generally twisted nematic layer can be written as where the matrix elements have been given before. For any linearly polarized light input, the output Stokes vector is given by where α is the input polarizer angle. S is in general elliptically polarized. Under special conditions, S will be linearly or circularly polarized. These are the conditions for optimal transmittive or reflective displays. 1. Linear polarization output (LP) A linearly polarized output requires that S3 = Gcos2α + Hsin2α = 0. There are two solutions. Solution I (LP1):