Optics: image projectors – Composite projected image – Multicolor picture
Reexamination Certificate
1997-08-07
2001-06-19
Dowling, William (Department: 2851)
Optics: image projectors
Composite projected image
Multicolor picture
C353S069000, C353S020000
Reexamination Certificate
active
06247816
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is directed to optical systems for projection displays, and more particularly, to optical systems employing spatial light modulators for forming a plurality of color images having additional optics for improved color convergence.
2. Description of the Prior Art
Optical systems for projection displays employing a plurality of spatial light modulators are known in the art. Generally, three spatial light modulators are used to form three color components of an image, typically, red, green and blue components. Light is first separated into the three colors, which are in turn projected onto a respective SLM to form the three color components of an image. The three color components are recombined and projected onto a screen. The three color images must be converged properly to produce a high quality projected image. In the known prior art systems, color convergence is not good at the corners of the screen and therefore the image quality is less than perfect. In addition, the prior art systems have the problem of polarization due to birefringence in the imaging path.
SUMMARY OF THE INVENTION
An optical system for a projection display employing three reflective spatial light modulators (SLM's) is described. Two of the three SLM imaging paths employ typical image combining and projection optical techniques. However, the third SLM imaging path employs a relay lens to produce an intermediate image of the SLM which is subsequently combined with the other two images. This approach has many advantages for high performance projection displays including high contrast, high optical efficiency, and in particular, enabling better color convergence.
White light from an arc lamp is separated within the illumination system into the three color components red (R), green (G) and blue (B). Each color component is directed onto one of three SLM's, each through its own polarizing beamsplitter (PBS) cube. In two of the three SLM's, image forming light is reflected from each SLM and passes through its respective PBS, and the two colors are then recombined using a dichroic coating. A lens then images the two-color image, and projects it onto a screen.
The third SLM, however, traverses a completely separate path. In this case, the image forming light reflected by that SLM and passing through the PBS is first imaged by a relay lens of approximately unity magnification to produce an intermediate image plane. This intermediate image (of the third color SLM) is then recombined with the first two color images using PBS or dichroic coating. The recombination is accomplished in a manner that ensures that the three color images are formed at the back focal distance of the projection lens. The full three-color image projected by the lens is thus comprised of two real SLM's and an intermediate image of the third SLM produced by the relay lens.
REFERENCES:
patent: 2747460 (1956-05-01), Calvi
patent: 4728185 (1988-03-01), Thomas
patent: 4836649 (1989-06-01), Ledebuhr et al.
patent: 4850685 (1989-07-01), Kamakura et al.
patent: 5032022 (1991-07-01), Sato et al.
patent: 5365287 (1994-11-01), Vollmer et al.
patent: 5374968 (1994-12-01), Haven et al.
patent: 5442413 (1995-08-01), Tejima et al.
patent: 5512967 (1996-04-01), Bohannon
patent: 5575548 (1996-11-01), Lee
patent: 5577826 (1996-11-01), Kasama et al.
patent: 5597222 (1997-01-01), Doany et al.
patent: 5621486 (1997-04-01), Doany et al.
patent: 5626409 (1997-05-01), Nakayama et al.
patent: 5695266 (1997-12-01), Kida et al.
patent: 6010221 (2000-01-01), Maki et al.
patent: 6034818 (2000-03-01), Sedmayr
patent: 6-82723 (1994-03-01), None
patent: 8-201756 (1996-08-01), None
Cipolla Thomas Mario
Doany Fuad Elias
Melcher Robert Lee
Singh Rama Nand
Dowling William
International Business Machines - Corporation
Morris Daniel P.
Scully Scott Murphy & Presser
LandOfFree
Optical system for projection displays using spatial light... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Optical system for projection displays using spatial light..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Optical system for projection displays using spatial light... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2472551