Optical: systems and elements – Holographic system or element – Using a hologram as an optical element
Patent
1994-11-03
1996-10-01
Fahmy, Wael M.
Optical: systems and elements
Holographic system or element
Using a hologram as an optical element
359 75, 359 76, 359102, G02F 11335, G02F 11337, G02F 113
Patent
active
055615406
ABSTRACT:
According to the state of the art, LC displays are known whose torsion angle is between about 180.degree. and 300.degree.. Such displays exhibit good independence of angle of view of white impression and contrast, but they are not gray scale capable and are not free of hysteresis. For that reason, the invention presents a display (10) whose product of plate separation (d) and anisotropy of the angle of refraction is equal to or greater than 0.45 and smaller than 0.65 .mu.m, whose torsion angle .phi. is between 260.degree. and 360.degree., whose liquid crystal molecules (18) have an approach angle .theta. between 7.degree. and 25.degree., and encompass a liquid crystal material between the substrate plates (11) in which the relationship of the elastic constant K.sub.3 to the elastic constant K.sub.1 is between 1.4 and 0.6. The angular relationships (.beta., .gamma.) of the polarization directions P.u, P.o with the respective orientation direction .eta..u, .eta..o is a function of torsion angle .phi.. An improvement of the contrast relationships is provided, if the relationship between the upper polarization direction P.o and the lower polarization direction P.u is smaller than 90.degree..
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Brosig Stefan
Waldmann Jurgen
Abraham Fetsum
Fahmy Wael M.
Nokia Technology GmbH
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