Optics: image projectors – Plural projection paths with single light source
Reexamination Certificate
1999-03-22
2001-01-09
Dowling, William (Department: 2851)
Optics: image projectors
Plural projection paths with single light source
C353S031000, C359S205100, C348S840000
Reexamination Certificate
active
06170953
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a laser video projector for projecting an image to a plurality of screens, and more particularly, to a laser video projector using laser as a light source for modulating light from the light source by an acousto-optic modulator (AOM) according to a video signal and projecting video information to a plurality of screens using a scanner.
2. Description of the Related Art
A flat panel display device such as a liquid crystal display or a cathode ray tube of a television set is a conventional representative video display means. However, the cathode ray tube or the liquid crystal display is more difficult to manufacture and the resolution becomes worse as the screen size increases. Accordingly, there are limits to the practical use of the cathode ray tube or the liquid crystal display the screen size of which becomes larger. Therefore, a method of enlarging an image displayed on the cathode ray tube or the liquid crystal display by a lens and projecting the enlarged image to a screen is used in order to realize a large screen.
A method of projecting red, green, and blue images to the screen one above the other using three cathode ray tubes and three lenses independently is disclosed in U.S. Pat. No. 4,942,525 and a method of composing images having the respective colors from the three cathode ray tubes and projecting the composed image to the screen by a lens is disclosed in U.S. Pat. No. 4,842,394.
The conventional video displaying method in the cathode ray tube or the liquid crystal display, used for displaying an image on a large screen has problems in that the picture projected to the screen is not clear since the displayed image is projected after being enlarged by the lens only and that the brightness is low since the output of the light source is limited since the video displaying means, in particular, an optical system can be damaged due to a temperature characteristic.
Also, in the conventional video projector such as the cathode ray tube or the liquid crystal display, an image is projected to a screen by a projector. Considering that the demand for outdoor advertisements using a large screens is remarkably increasing, the fact that it is not possible to display an image on a plurality of screens from a video projector may deteriorate the effect of advertisement. Furthermore, when the image is projected after being enlarged by the lens only, the picture quality worsens when the image is projected to a plurality of screens.
SUMMARY OF THE INVENTION
To solve the above problem, it is an object of the present invention to provide a laser video projector for projecting an image having high contrast and high brightness to a large screen, in particular, to a plurality of large screens.
Accordingly, to achieve the above object, there is provided a laser video projector for projecting an image to a plurality of screens, comprising a light source for outputting a beam of white light, light separating means for separating the beam of the white light into beams of monochromatic lights having first, second, and third wavelengths, light modulating means for modulating the beams of the monochromatic lights according to a chrominance signal, light combining means for combining the monochromatic lights modulated by the light modulating means into a beam, light scanning means for scanning the combined beam of the modulated monochromatic lights, thus forming an image; a multi-screen projecting optical system for changing the light path so that the image formed by the light scanning means is displayed on multiple screens, and a plurality of screens corresponding to the plurality of images.
In the present invention, the light separating means preferably comprises a first dichroic mirror for reflecting at least 99% of monochromatic light of a first wavelength from the beam of the white light and transmitting at least 95% of monochromatic light of second and third wavelengths, a second dichroic mirror for reflecting at least 99% of monochromatic light of the second wavelength and transmitting at least 95% of monochromatic light of the third wavelength, and a high reflection mirror for reflecting at least 99% of the monochromatic light of the third wavelength.
In the present invention, the light modulating means preferably comprises three acousto-optic modulators for modulating the beams of the monochromatic lights of the first, second, and third wavelengths. The light combining means preferably comprises a third dichroic mirror for transmitting the beam of the monochromatic light of the first wavelength and reflecting the beam of the monochromatic light of the second and third wavelengths, a fourth dichroic mirror for reflecting the monochromatic light of the second wavelength and transmitting the monochromatic light of the third wavelength, a high reflection mirror for reflecting the monochromatic light of the third wavelength. The multi-screen projecting optical system preferably comprises a plurality of reflecting mirrors.
REFERENCES:
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patent: 5255082 (1993-10-01), Tamada
patent: 5317348 (1994-05-01), Knize
patent: 5365288 (1994-11-01), Dewald et al.
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patent: 6020937 (2000-02-01), Bardmesser
Hwang Young-mo
Lee Jin-Ho
Burns Doane Swecker & Mathis L.L.P.
Dowling William
Samsung Electronics Co,. Ltd.
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