Optical: systems and elements – Polarization without modulation – Polarizarion by dichroism
Patent
1998-04-16
2000-08-22
Spyrou, Cassandra
Optical: systems and elements
Polarization without modulation
Polarizarion by dichroism
359494, 359495, G02B 530
Patent
active
061081329
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a polarization illuminating device for uniformly illuminating a rectangular illumination region or the like by using polarized lights whose directions of polarization are aligned, and to a projection type display device using this polarization illuminating device. More specifically, the present invention relates to a structure for synthesizing lights emitted from two light source sections while aligning the directions of polarization thereof.
2. Description of Related Art
In a liquid crystal display device using a modulator of a type which modulates a particular polarized light like a liquid crystal element, only one of two polarization components emitted from the light source can be utilized. Thus, to obtain a bright projection image, it is necessary to enhance the efficiency in the utilization of light. However, there is a limitation in enhancing the efficiency in the utilization of light in a projection type display device using only one light source. Thus, using a plurality of light sources to augment the quantity of light is a means for obtaining a bright projection image.
However, simply arranging a plurality of light sources only results in the area of the light source images being correspondingly augmented, and the quantity of light per fixed area is the same as when only one light source is used. Thus, in this case, there is substantially no increase in quantity of light per fixed area even though a plurality of light sources are used.
Even when the quantity of light is augmented by using a plurality of light sources, if only one of the two polarization components of the light emitted from the light source can be utilized, the rest of the quantity of light is wasted, and half the effectiveness is lost.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a polarization illuminating device in which a plurality of light sources are used without enlarging the area of the light source image, which makes it possible to utilize both polarization components and which makes it possible to project a very bright projection image.
The optical element of the present invention is an optical element substantially formed as a hexahedron and comprises a first polarization separation layer for separating light impinging upon a first surface of the hexahedron into first and second polarized lights whose planes of polarization are orthogonal to each other and outputting the first polarized light toward a third surface of the hexahedron and the second polarized light toward a fourth surface of the hexahedron, and a second polarization separation layer for separating light impinging upon a second surface of the hexahedron into the first and second polarized lights and outputting the second polarized light toward the fourth surface of the hexahedron and the first polarized light toward a fifth surface of the hexahedron.
By adopting the optical element of the present invention as the polarization separation/synthesis optical element of a polarization illuminating device as described below, the above problem can be solved.
The polarization illuminating device of the present invention comprises: a polarization separation/synthesis optical element equipped with two polarization separation layers and formed substantially as a hexahedron; first and second light source sections respectively arranged on the first and second surface sides of the polarization separation/synthesis optical element; a first converging reflection optical element arranged on a third surface side of the polarization separation/synthesis optical element and equipped with a plurality of converging reflection elements each adapted to substantially reverse the traveling direction of the incident light and form a convergent image; a second converging reflection optical element arranged on a fourth surface side of the polarization separation/synthesis optical element and equipped with a plurality of converging reflection elements each adapted t
REFERENCES:
patent: 5295018 (1994-03-01), Konuma et al.
patent: 5485310 (1996-01-01), Inada
Patent Abstracts Of Japan, "Lighting Device and Projection Display Device Using It", JP-A-08-211 329, Aug. 20, 1996.
Patent Abstracts Of Japan, "Polarizing Illuminator and Projection Type Display Device Using The Same", JP-A-08-220 475, Aug. 30, 1996.
Cherry E.
Seiko Epson Corporation
Spyrou Cassandra
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