Optics: image projectors – Color filter
Reexamination Certificate
1999-12-29
2001-03-20
Dowling, William (Department: 2851)
Optics: image projectors
Color filter
C353S020000, C353S031000, C348S743000
Reexamination Certificate
active
06203160
ABSTRACT:
BACKGROUND OF THE INVENTION
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.
SUMMARY OF THE INVENTION
Accordingly, one object of this invention is to provide a high efficiency liquid crystal display projection system that can effectively use the energy of s-polarized light and p-polarized light emitted from the light source.
Another object of this invention is to provide a high efficiency liquid crystal display projection system that can simplify the structure of light splitting/combining prism basing on the feature that the effective aperture ratio of a reflective liquid crystal light valve is larger than 85%.
The other object of this invention is to provide a high efficiency liquid crystal display projection system that can simplify the liquid crystal display projection system by using a ferro-electric liquid crystal panel having a fast time response.
To achieve the above objects, this invention uses a visible light broadband polarizing beam splitter, in which the s-polarized light and p-polarized light must meet the following requirement:
R
S
/R
P
≧200
T
P
/T
S
≧200
At the same time, instead of six liquid crystal panels used in a conventional liquid crystal display projection system, this invention uses two ferro-electric liquid crystal light valves having a fast time response, and uses a color disk to replace the dichroic filters used in the conventional liquid crystal display projection system. Furthermore, this invention uses a broadband polarizing beam-splitting prism to combine/split light. Therefore, the volume of the liquid crystal display projection system is significantly reduced. The cost is lowered and the structure is simplified.
REFERENCES:
patent: 5042925 (1991-08-01), Broer et al.
patent: 5805243 (1998-09-01), Hatano et al.
patent: 5833338 (1998-11-01), Barak
patent: 5863125 (1999-01-01), Doany
patent: 5921650 (1999-07-01), Doany et al.
patent: 5982541 (1999-11-01), Li et al.
patent: 5984478 (1999-11-01), Doany et al.
patent: 5993007 (1999-11-01), Jung
patent: 6005722 (1999-12-01), Butterworth et al.
Beyer Weaver & Thomas LLP
Dowling William
Industrial Technology Research Institute
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