Optics: image projectors – Color filter
Reexamination Certificate
2000-12-22
2002-09-17
Adams, Russell (Department: 2851)
Optics: image projectors
Color filter
C348S743000, C353S031000
Reexamination Certificate
active
06450649
ABSTRACT:
FIELD OF TECHNOLOGY
The invention relates to a color projection system comprising a light source, a rotatable drum having a plurality of differently colored bands, and a light modulation panel on which light beams reflected by the colored bands can be directed by way of scrolling.
BACKGROUND AND SUMMARY OF THE INVENTION
In such a color projection system as described in non-prepublished European patent application EP 99202414.1, the light beam coming from the light source is directed onto the drum and split by the differently colored bands into light beams having complementary colors, while a light beam colored in conformity with a color of the band is directed onto the light modulation panel. The complementary color is absorbed by the band. This means that when using split colors of red, green and blue, one color of a light beam projected on a band is directed onto the light modulation panel, whereas the other two colors are absorbed. This results in a two-thirds loss of light.
It is an object of the invention to provide a color projection system in which there is less loss of light.
In the color projection system according to the invention, this object is achieved in that the color projection system further comprises means for directing the light beam from the light source onto a first plurality of juxtaposed bands, means for splitting and reflecting the light beam on each band into light beams having complementary colors and different directions of polarization, means for directing light beams having a first direction of polarization onto the light modulation panel, and means for reflecting light beams having a second direction of polarization onto a second plurality of bands of the drum which is shifted by at least one band with respect to the first plurality of bands.
Instead of absorbing the color(s) complementary to the colored band, these colors are reflected and subsequently reflected again into the direction of the drum, while the colors reach another band. This band has the same color as one of the colors reflected again so that this band as yet directs the relevant color onto the light modulation panel. In this way, a larger part of the light beam coming from the light source is directed onto the light modulation panel.
These and other aspects of the invention are apparent from and will be elucidated with reference to the embodiments described hereinafter.
REFERENCES:
patent: 6217174 (2001-04-01), Knox
patent: 6266105 (2001-07-01), Gleckman
patent: 6334685 (2002-01-01), Slobodin
Adams Russell
Koninklijke Philips Electronics , N.V.
Sever Andrew
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