Optics: image projectors – Polarizer or interference filter
Patent
1994-12-15
1997-05-06
Dowling, William
Optics: image projectors
Polarizer or interference filter
359495, 359497, G03B 2114
Patent
active
056264089
ABSTRACT:
The invention relates to an illumination system (7) for a colour image projection device (1). The illumination system (7) comprises a radiation source (3) for generating an unpolarized radiation beam (5) and at least a cholesteric mirror (9, 10, 11, 12, 13, 14) for wavelength-selective splitting of the radiation beam (5) into at least two sub-beams of different wavelengths. A composite circular polarizer (35) for directly converting the unpolarized radiation beam (5) into circularly polarized sub-beams jointly forming one beam is arranged in the path of the unpolarized radiation beam (5) between the radiation source (3) and the cholesteric mirror (9). The composite circular polarizer (35) comprises a polarization-sensitive beam splitter (43) which splits the unpolarized radiation beam (5) into two mutually perpendicularly and linearly polarized sub-beams, and a polarization converter (51, 53; 59, 61). The circularly polarized monochrome sub-beams are subsequently modulated, either or not after passage through .lambda./4 plate (63, 65, 67), by a corresponding number of image display panels (27, 29, 31) and projected as an image via a projection lens system (33).
REFERENCES:
patent: 5042925 (1991-08-01), Broer et al.
patent: 5184248 (1993-02-01), de Vaau et al.
patent: 5387953 (1995-02-01), Minoura et al.
"New Liquid Crystal Polarized Color Projection Principle": by M. Schadt and J. Funfschilling in Japanese Journal of Applied Physics, vol. 29, No. 10, Oct. 1990, pp. 1974-1984.
"Retardation Film for STN-LCDs `Nrf`" of the film of Nitto Denko in SID '92 Exhibit Guide, Society for Information Display, May 17-22, 1992, Boston, Mass.
"Principles of Optics" by M. Born and E. Wolf, 6th edition, Pergamon Press, pp.47-51, 615-618.
Search Report.
Broer Dirk J.
Heynderickx Ingrid E. J. R.
Dowling William
Egbert Walter M.
U.S. Philips Corporation
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