Optical: systems and elements – Polarization without modulation – Polarizarion by dichroism
Patent
1998-12-21
2000-11-07
Schuberg, Darren
Optical: systems and elements
Polarization without modulation
Polarizarion by dichroism
359485, 349 95, 353 20, 362 19, G02B 530
Patent
active
061444928
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to an optical block, which may be of a small size, for applying light efficiently to a display device such as a liquid crystal panel, and a display apparatus.
BACKGROUND ART
Recently, display apparatus such as projectors, television receivers, and computer display units which employ optical devices such as liquid crystal panels or the like are in widespread use. In a display apparatuses which employs a liquid crystal panel or the like, light emitted from a light source such as a metal halide lamp, a halogen lamp, or the like is applied to a liquid crystal panel having color filters (R, G, B), and the liquid crystal panel displays a colored video image as its output light. The output light from the liquid crystal panel is projected onto a screen by a projection lens.
Light radiated from an ordinary light source has two planes of polarization that are generally referred to as a P-polarized component (hereinafter referred to as a P wave) and an S-polarized component (hereinafter referred to as an S wave). The display apparatus has polarizing means positioned such that light emitted from the light source is applied to the polarizing means before being applied to the liquid crystal panel. The polarizing means applies light having a plane of polarization which is either the P wave or the S wave depending on a polarizer disposed in front of the liquid crystal panel.
If rays of randomly polarized light are applied to polarizing beam splitters (hereinafter referred to as a PBS) disposed in prisms, for example, at a given angle, then a P wave passes through the PBSs and an S wave is reflected by the PBSs. Both the P and S waves are refracted by end faces of the prisms into parallel rays of light, and only the S wave is converted into a P wave by being transmitted through a .lambda./2 plate. Alternatively, the S wave is converted into a P wave by being refracted by end faces of the prisms so as to be parallel to the direction of travel of the P wave that has passed through the PBSs, or reflected toward a .lambda./2 plate by a reflecting means such as a mirror or the like. According to the former process, one unit of optical block is employed. According to the latter process, one or two units of optical block are symmetrically arranged.
FIG. 12 shows the structure of a conventional polarizing means and optical paths. A light source 40 comprises a halogen lamp, a metal halide lamp, or the like. Light emitted from the light source is passed through an optical block 50, which applies only a P wave to a liquid crystal panel (not shown). The optical block 50 comprises a plurality of prisms 50a-50f of glass which are bonded together. PBSs 52 are disposed between the prisms 50b, 50e and between the prisms 50c, 50d, and wave plates 53 are disposed on front faces of the prisms 50a, 50f. P+S waves emitted from the light source 40 are represented by solid arrows. The path of a P wave separated by the optical block 50 is represented by white blank arrows, and the path of an S wave separated by the optical block 50 is represented by hatched arrows.
P+S waves emitted from the light source 40 are separated by the PBSs 52. The P wave passes through the PBSs 52 and is applied to the liquid crystal panel. The S wave is reflected by the PBSs 52, then reflected forward by the prisms 50a, 50f, and converted by the wave plates 53 into a P wave, which is applied to the liquid crystal panel. Therefore, only the P wave is emitted from front faces of the prisms 50d, 50e and the wave plates 53. In this manner, either one of the P+S waves emitted from the light source 40 is applied by the optical block 50 to the non-illustrated liquid crystal panel.
If the optical block 50 were not employed, then the aperture of the light source 40 would be similar in shape to the effective area of the liquid crystal panel. However, a liquid crystal panel for displaying horizontally long images having an aspect ratio of 16:9, for example, has its side areas that cannot uniformly be irradiated with light, and henc
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Iwaki Takaaki
Iwamura Atsushi
Katsuragawa Hideki
Kawai Toru
Maioli Jay H.
Schuberg Darren
Sony Corporation
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