Small reflective type liquid crystal projection device

Details Small reflective type liquid crystal projection device Small reflective type liquid crystal projection device

2002-05-09

2003-10-28

Fuller, Rodney (Department: 2851)

Optics: image projectors

Composite projected image

Multicolor picture

C353S020000, C353S033000, C353S081000, C349S009000

Reexamination Certificate

active

06637890

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a liquid crystal projection system and, more particularly, to a liquid crystal projection optical system adopting reflective type of liquid crystal display.
BACKGROUND OF THE INVENTION
General reflective type liquid crystal projection optical engines have different architectures. For example, companies such as JVC, Philips, Color Link, RDI, and Aurora System produce reflective type liquid crystal projection devices of different structures. Almost all the structures adopt an X-prism. Color Link and RDI adopt their own color selectors to achieve the object of light-splitting projection.
Generally, reflective type liquid crystal projection devices mainly adopt the X-prism architecture to let the three primary colors of red (R), green (G), and blue (B) enter three different sets of polarization beam splitter (PBS) and then combine together. Three light beams are the common design idea. They differ only in variation of light projection system. Different light projection systems have different usage efficiencies of light energy and sizes of occupied volume. However, the above projection devices have more complicated structures, and thus have the disadvantages of large volume and higher cost. Moreover, the highest usage efficiency of the three primary colors of R, G, and B cannot be accomplished.
Accordingly, the present invention aims to propose a reflective type liquid crystal projection device, which can shrink the volume of optical system to shorten the distance of incident polarized light to the reflective type LCD, thereby effectively enhancing the imaging quality of projection device and reducing the cost.
SUMMARY AND OBJECTS OF THE PRESENT INVENTION
The primary object of the present invention is to propose a small reflective type liquid crystal projection device, which uses an X-prism matched with a newly invented 3D light projection system to combine polarized light beams of the three primary colors of R, G, and B into a single light beam so as to achieve the highest use efficiency.
Another object of the present invention is to propose a reflective type liquid crystal projection device having both the advantages of small volume and reduced cost.
To achieve the above objects, the present invention comprises an incident light source for providing a parallel incident light, which passes through a diffusive mirror set and a collective mirror set and is then converted into an S-polarization light. A first PBS is then used to split the S-polarization light into three light beams of the three primary colors, which are respectively reflected and transmitted. After at least three totally reflective mirrors arranged in 3D space reflect the third primary color to the first PBS and reflect the first and second primary colors to a second dichromatic mirror, the two primary colors are projected toward a second PBS and a third PBS, respectively. Next, after three reflective type liquid crystal plates convert the three primary colors reflected by the PBSs into P-polarization lights, which are transmitted through the PBSs and then combined at an X-prism to obtain an output light beam. Finally, the output light beam is projected to a screen by a projection object lens.
The various objects and advantages of the present invention will be more readily understood from the following detailed description when read in conjunction with the appended drawings, in which:


REFERENCES:
patent: 5772299 (1998-06-01), Koo et al.
patent: 6345895 (2002-02-01), Maki et al.
patent: 6429906 (2002-08-01), Sekine et al.
patent: 6439725 (2002-08-01), Na

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