Optics: image projectors – Composite projected image – Multicolor picture
Reexamination Certificate
2000-04-19
2001-07-10
Adams, Russell (Department: 2851)
Optics: image projectors
Composite projected image
Multicolor picture
C353S038000, C353S084000, C349S108000, C348S743000
Reexamination Certificate
active
06257728
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a color projection system comprising at least a light source, at least an integrator plate arranged in front of the light source and comprising a plurality of juxtaposed lens elements, an electro-optical light modulation panel arranged in front of the integrator plate, at least a projection lens preceding the light modulation panel, and a movable color filter which is provided with a plurality of parallel extending, differently colored strips.
In such a color projection system known from JP-A-4.54093 (Toshiba Corporation), the color filter precedes the light modulation panel. The color filter has at least three differently colored strips. The colors of the strips are red, blue and green. The color filter is moved in front of the light modulation panel while simultaneously a part of the image to be projected corresponding to the color of the color strip facing the relevant part is generated on each portion of the light modulation panel. By moving the color filter relatively quickly and simultaneously adapting the parts of the image to be projected, which parts are generated on the light modulation panel, the red, blue and green part of the image is generated on each part of the light modulation panel and projected through the oppositely located colored strip and the projection lens. By projecting the three different colors of an image rapidly one behind the other, a fully colored image is observed by the human eye.
It is an advantage of such a color projection system that only one light modulation panel needs to be used.
However, it is a drawback of such a color projection system that the color filter is located in the imaging portion so that the color filter must have a sufficient optical quality, while it must be moved relatively very accurately and must be mechanically stable so as to ensure a qualitatively satisfactory projected image. Moreover, each colored strip should be moved through a relatively large distance of the complete light modulation panel.
SUMMARY OF THE INVENTION
It is an object of the invention to provide a relatively compact color projection system in which the color filter is positioned in a simple manner between the light source and the light modulation panel, while, moreover, the color projection system is relatively insensitive to inaccuracies of the color filter.
In the color projection system according to the invention, this object is achieved in that the color filter is located opposite the integrator plate, the color filter and integrator plate being movable relative to each other in a direction extending parallel to the integrator plate, while at least two differently colored strips are located opposite each lens element, strips of the same color having the same orientation with respect to each lens element.
As it were, the same color filter having a plurality of colored strips is thus located opposite each lens element. The light beams exiting from the lens elements of the integrator plate are integrated to a light spot imaged on the light modulation panel, which light spot, dependent on the colored strips located opposite the lens elements, has a structure corresponding thereto. The parts of the image to be projected, associated with the colored portions, are generated on the light modulation panel.
An inaccuracy of a single colored strip opposite a single lens element will have a relatively small influence on the eventual light spot imaged on the light modulation panel. Since a lens element is relatively small with respect to the light modulation panel, the distance through which the color filter must be moved per image to be fully projected is relatively small. This relatively small movement can be performed in a relatively simple and accurate manner.
These and other aspects of the invention are apparent from and will be elucidated with reference to the embodiments described hereinafter.
REFERENCES:
patent: 5467206 (1995-11-01), Loiseaux et al.
patent: 5650832 (1997-07-01), Poradish et al.
patent: 454093 (1992-02-01), None
Bergman Anthonie H.
Bierhuizen Serge J. A.
Shimizu Jeffrey A.
Adams Russell
Cruz Magda
U.S. Philips Corporation
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