Optics: image projectors – Unitary plural refracting surfaces
Reexamination Certificate
1999-03-19
2001-07-24
Dowling, William (Department: 2851)
Optics: image projectors
Unitary plural refracting surfaces
C353S102000
Reexamination Certificate
active
06264332
ABSTRACT:
BACKGROUND
1. Field of the Invention
The present invention relates to an illumination apparatus and a projection type image display apparatus using it.
2. Description of the Related Art
In recent years, liquid crystal projectors have become popular for many uses because they fulfill user's desires for a large area display in applications such as a personal computer or a television, and improvements in the technology relating to liquid crystals have made it easier to manufacture a large area display.
Although the liquid crystal projector and a CRT (Cathode-Ray Tube) projector have similar functions, the former provides better image quality and is smaller and lighter than the latter. However, conventional liquid crystal projectors do not provide a sufficiently bright screen, and an improvement in brightness is now desired in many applications. It is common to use a combination of a high-luminance lamp and a paraboloidal or a ellipsoidal reflector as a light source to improve brightness. However, the generated light beam is poor in illuminance uniformity. Therefore it is necessary to improve the uniformity of the screen luminance.
SUMMARY OF THE INVENTION
The present invention has been made in view of the above-mentioned circumstances and is intended to solve the above-mentioned problems. In particular, a purpose of the present invention is to provide an illumination apparatus which can maintain higher uniformity in illuminance distribution even in a case where part of an optical system has nonuniform characteristics, for instance, a light source has a nonuniform emission distribution. This invention also provides a projection type image display apparatus which has higher uniformity in luminance distribution by employing the illumination apparatus. Additional purposes and advantages of the invention may be apparent from the following description or may be learned by practice of the invention.
The present invention provides an illumination apparatus for illuminating a light beam onto a target surface, including a beam shape converter that converts a sectional shape of the light beam into a different shape, a beam divider that spatially divides the converted light beam into plural light beams, and a beam superimposer that superimposes the plural light beams onto the target surface.
In accordance with one aspect of the present invention, a projection type image display apparatus for projecting an image onto a screen, includes a light source that emits a light beam, a beam shape converter that converts a sectional shape of the light beam into a different shape, a beam divider that spatially divides the converted light beam into plural light beams, a beam superimposer that superimposes the plural light beams onto a target surface, a processing unit that supplies a signal so as to display an image on the target surface, and a projection lens that projects the image onto the screen by the superimposed beam.
According to a preferred embodiment of the present invention, the beam shape converter may convert a sectional shape of the light beam from an approximately circular shape to an approximately rectangular shape. The converted light beam may have the rectangular sectional shape at a position where the beam divider is located. The beam divider may include an optical element having a plurality of optical surfaces, and the converted light beam passes through the optical element so that the light beam is spatially divided into the plural light beams.
In the illumination apparatus, a light intensity distribution on the target surface may have higher uniformity than that on the beam shape converter. The beam shape converter may convert the sectional beam shape in such a manner that boundaries of the optical surfaces of the optical element are more illuminated than the center area of the optical surfaces of the optical element.
The present invention may also include an imaging element for allowing both positions of the beam superimposer and the target surface to have a conjugate relationship with each other. The superimposer may further include a beam deflector that deflects the plural light beams, and a beam collimator that converts the deflected plural light beams into parallel light beams, so as to superimpose the divided beams on the target surface.
Furthermore, the present invention also provides a method of illuminating a light beam onto a target surface, including steps of converting a sectional shape of the light beam into a different shape, spatially dividing the converted light beam into plural light beams, and superimposing the plural light beams onto the target surface.
REFERENCES:
patent: 4770525 (1988-09-01), Umeda et al.
patent: 5098184 (1992-03-01), Van Den Brandt et al.
patent: 5833341 (1998-11-01), Kimura et al.
patent: 5973841 (1999-10-01), Watanabe
patent: 10-186301 (1998-07-01), None
Honguh Yoshinori
Kitamura Masaru
Mihara Hisayuki
Takashima Yuzuru
Dowling William
Foley & Lardner
Kabushiki Kaisha Toshiba
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