U.S. Philips Corporation

Franciscus J Wortel

Hendrik Adrianus Van Sprang

Ingrid E Heynderickx

Peter E Wierenga

Henricus G Koopman

An optical device for combining three sub-beams of different colors to one color beam is disclosed having a first and a second color-selective reflector arranged on transparent plate-shaped substrates, the first reflector reflecting a first of said sub-beams, the second reflector reflecting the first sub-beam and a second of said sub-beams and a third of said sub-beams passing through the second reflector and its substrate. A transparent plate is arranged in the path of the first sub-beam and in front of the first reflector, the transparent plate having a product of refractive index and thickness equal to that of the substrates of the first and second reflectors. An astigmatism correcting element is positioned in the path of the color beam.

Beam-combining device and color image projection apparatus provided with

An optical device for combining at least two sub-beams (b.sub.G, b.sub.R, b.sub.B) of different colours to one colour beam (b.sub.C) is described, which device comprises at least one colour-selective reflector which is arranged on a transparent plate-shaped substrate. By using a correction element composed of a first sub-element chosen from the group of cylindrical lens and obliquely arranged spherical lens, and a second sub-element chosen from the group of plane-parallel plate, wedge and prism, aberrations caused by the substrate in a sub-beam can be corrected.

In a projection display device based on one or more (twisted nematic) LCDs (4), simple temperature compensation is possible by optimizing the d..DELTA.n value (n) at the maximal operating temperature. The associated transmission/voltage characteristics at different temperatures then extend substantially parallel so that it is possible to compensate for temperature changes by means of a simple voltage compensation.

Temperature compensated color LCD projector

A display cell which contains a liquid crystalline compound having a tilted orientation and a tilt angle of 8.degree.-50.degree., in which an orientation layer is used of a cyclo-aliphatic polyether.

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Eindhoven, Netherlands

Franciscus J Wortel