Transmission characteristics of a twisted nematic liquid-crystal layer*

An approximate analytical expression is calculated for the transmission of thin twisted nematic layers situated between a polarizer/analyzer pair. The approximation assumes that the twist angle of the nematic liquid crystal is smaller than the maximum retardation of the cell. The direction of the incident light is assumed to be parallel to the normal of the electrode. This configuration is analyzed for a general arrangement of polarizer and analyzer; the general result is evaluated for the case of the polarizer parallel and analyzer perpendicular to the liquid-crystal optical axis on the input and output electrodes, respectively. The results show that in the case of a thin twisted nematic layer the transmission depends on the thickness of the layer, on the birefringence of the liquid crystal, and on the wavelength of the light. This is a departure from the well-known independence of the transmission on these parameters for a thick twisted nematic layer. The analysis also shows that the transmission through thin layers can be minimized by tuning the layer thickness to particular values that depend on wavelength and on liquid-crystal birefringence. In this way, high image contrast can be obtained even for thin liquid-crystal layers.

[1]  J. Grinberg,et al.  Photoactivated birefringent liquid-crystal light valve for color symbology display , 1975, IEEE Transactions on Electron Devices.

[2]  S. Kobayashi,et al.  Electro-optical properties of twisted nematic liquid crystals : An application to voltage controllable color formation , 1975 .

[3]  M. Wada,et al.  Liquid-crystal color display by DAP-TN double-layered structure , 1974 .

[4]  I. A. Shanks,et al.  Electro-optical colour effects by twisted nematic liquid crystal , 1974 .

[5]  H. Kodera,et al.  GaAs 50 GHz Schottky-barrier IMPATT diodes , 1974 .

[6]  Dwight W. Berreman,et al.  Optics in smoothly varying anisotropic planar structures: Application to liquid-crystal twist cells* , 1973 .

[7]  Terry J. Scheffer,et al.  New multicolor liquid crystal displays that use a twisted nematic electro‐optical cell , 1973 .

[8]  G. Meier,et al.  Optical Properties of Cholesteric Liquid Crystals , 1973 .

[9]  G. Meier,et al.  Light propagation in helicoidal structures , 1973 .

[10]  Rasheed M. A. Azzam,et al.  Simplified Approach to the Propagation of Polarized Light in Anisotropic Media—Application to Liquid Crystals* , 1972 .

[11]  M. Schadt,et al.  Voltage-Dependent Optical Activity of a Twisted Nematic Liquid Crystal , 1971 .

[12]  G. H. Conners.  Electromagnetic Wave Propagation in Cholesteric Materials , 1968 .

[13]  S. Chandrasekhar,et al.  Optical rotatory power of liquid crystals , 1968 .

[14]  J. Billard.  Des Ondes Électromagnétiques qui ne Satisfont Pas aux Conditions d'Airy Peuvent se Propager dans les Lames Nématiques Hélicoïdales , 1967 .

[15]  S. Ramaseshan.  Faraday effect and birefringence—I , 1951 .

[16]  H. Vries,et al.  Rotatory Power and Other Optical Properties of Certain Liquid Crystals , 1951 .