Optics: image projectors – Cabinet encloses projector and one side of screen – Focus or variable magnification
Reexamination Certificate
2000-07-07
2003-01-28
Adams, Russell (Department: 2851)
Optics: image projectors
Cabinet encloses projector and one side of screen
Focus or variable magnification
C353S033000, C353S034000, C353S037000, C353S078000, C353S094000, C353S101000, C359S196100, C359S200700, C359S202100, C359S205100, C359S210100, C359S211200, C359S218100, C359S221200, C359S226200, C359S256000, C359S259000, C359S460000
Reexamination Certificate
active
06511186
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to rear projection systems, and more particularly to compact rear projection systems that use separate optics for various areas of a viewing screen.
BACKGROUND OF THE INVENTION
Rear projection imaging systems typically include an image generation source, optics to enlarge and direct the image and a transmission screen for displaying the enlarged image. The image source can be of many different types, including cathode-ray tubes and liquid crystal displays (LCDs). In simple systems, the optics generally include a lens, such as a combined convex glass lens element and a methacrylic resin lens element, and a turning mirror for directing the image toward the screen. The transmission screens of typical systems generally include diffusing material, lenticular lens sheets and Fresnel lens sheets, which are intended to project a wide image with uniform brightness.
In operation, the image source is positioned behind the transmission screen and provides a small, bright image to the projecting lens. The projecting lens enlarges the image and directs it to the reflective surface of the turning mirror. The turning mirror reflects the image to the transmission screen. The lens sheets in the transmission screen further enlarge the image and collimate the projected light. The audience views the projected image from the transmission screen.
The depth dimension of known rear projection systems is constrained by the angle of incidence on and within the transmission screen's Fresnel lens. To make a compact rear projection package, a short focal length lens is required. A decreasing focal length increases the field of view as measured at the screen. As the field of view increases, the angles of incidence in air and within the Fresnel lens eventually approach the critical angle, causing transmission to drop to zero. Even before the angle of incidence reaches the critical angle, the angle of incidence will exceed the Brewster angle. Exceeding the Brewster angle can cause the S (perpendicular) and P (parallel) polarization transmission coefficients to diverge, resulting in image distortions, such as non-uniformity in brightness across the screen.
SUMMARY OF THE INVENTION
A projection system according to the principles of the invention tailors optics to various regions of a viewing screen. In one aspect of the invention, an image projection system includes an image generator, a viewing screen and a focus and aim component (FAC). The FAC is disposed to receive light corresponding to portions of the image from the image generator. The FAC deflects and focuses the light as a function of a position on the screen. An exemplary FAC includes a light-focusing device, such as a lens, and a light-deflecting device, such as a prism. The devices are disposed to receive a light beam in tandem representative of an image portion, such as a pixel. The light-deflecting device aims, and the light-focusing device focuses, the beam as a function of spot position on a screen. Another example of a light valve is a digital micro mirror device (DMD) or a digital light processor (DLP).
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Burstyn Herschel Clement
Lurie Michael J.
Adams Russell
Burke W. J.
Cruz Magda
Sarnoff Corporation
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