1. Field of the Invention
This invention relates to project systems, particularly to high efficiency liquid crystal display (LCD) projection systems.
2. Description of Prior Art
With the advent of commercially viable LCD projection systems, substantial research and development resources have been directed to LCD projection systems having higher brightness, higher pixel resolution, lighter weights, and lower cost. Recent developments have led to the development of reflective liquid crystal light valves, which can significantly increase aperture ratios. In IBM J. Res. Develop. Vol. 42, No. 3/4, 1998 by R. L. Melcher et al., LCD devices having pixel resolutions in accord with SXGA and QXGA format are disclosed.
Two subjects associated with the current design of optical devices are the design of light splitting/combining components and the effective use of light energy. Such light splitting and combining effects have been discussed by R. L. Melcher et al., in Micro LC Panel of S-V, Inc. and in the U.S. Pat. No. 5,786,937 to C. W. Chu et al. However, these technologies still have problems overcoming the requirements of low cost and high resolution. To that end, the U.S. Pat. No. 5,339,158 to Akiyama et al. discloses a single element called an "X-prism", which combines the light combining and light splitting effects such that the volume of the optical devices is significantly reduced. However, it is difficult to manufacture an X-prism.
Regarding other related art concerning the effective use of light source energy, the P/S converter disclosed in SID 97 Digest, pp. 993-996, 1997, by Itoh et al. is most widely used. Other polarization converters used in light sources are disclosed in U.S. Pat. Nos. 5,530,489 and 5,513,752.
The applicant has disclosed a liquid crystal display projection system which effectively uses light source energy. Referring to FIG. 1, a conventional liquid crystal display project system comprises: a light source 10; a visible light polarizing beam splitter 12; dichroic mirrors 14, 18 that reflect red light and transmit blue and green light; dichroic mirrors 16, 20 that reflect blue light and transmit green light; reflective liquid crystal panels 22, 24, 26, 28, 30, and 32; and projection lens 34. However, the structure of this conventional system has proven to be too complex.