Liquid crystal cells – elements and systems – Liquid crystal system – Projector including liquid crystal cell
Reexamination Certificate
1996-11-18
2001-12-18
Ton, Toan (Department: 2871)
Liquid crystal cells, elements and systems
Liquid crystal system
Projector including liquid crystal cell
C349S095000, C353S031000, C359S630000
Reexamination Certificate
active
06331879
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a liquid crystal projector provided with an illumination, optical system including a polarization changing optical system and an optical integrator.
In the conventional field of liquid crystal projectors, there has been known a liquid crystal projector provided with an illumination optical system including a polarization changing optical system and an optical integrator to obtain a bright projected image having a uniform distribution of illuminance as disclosed in Japanese Unexamined Patent Publications Nos. (HEI)6-265887 and (HEI)7-120753.
However, the above liquid crystal projector has a problem that the polarization changing optical system is likely to be degraded by heat because of its position in proximity to a light source.
Further, in the above liquid crystal projector, a polarization change is completed in a position more toward the light source than where the beam is incident on the optical integrator, the dimension of the illumination optical system in a direction normal to its main optical axis disadvantageously increases. Furthermore, since spaces are required to install the polarization changing optical system and the optical integrator, respectively, the dimension of the illumination optical system in a direction along its main optical axis disadvantageously increases. There are also problems that the polarization changing optical system making effective use of the light from the light source has a large size and a complicated construction.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a liquid crystal projector provided with an illumination optical system which has overcome the problems residing in the prior art.
It is another object of the present invention to provide a liquid crystal projector provided with an illumination optical system which is compact despite the use of a polarization changing optical system and an optical integrator.
It is still another object of the present invention to provide a liquid crystal projector provided with an illumination optical system which has little likelihood of being degraded by heat from a light source despite the use of a polarization converting optical system and an optical integrator.
It is yet still another object of the present invention to provide a liquid crystal projector provided with an illumination optical system which has a simple construction and utilizes light at high efficiency.
According to one aspect of the present invention, a liquid crystal projector comprising: a liquid crystal panel; an illumination optical system for illuminating the liquid crystal panel, the illumination optical system including: a light source which emits a beam of light; a first lens array and a second lens array arranged in this order from the light source, the first and second lens arrays each having a plurality of lenses; and a polarization changing optical system arranged between the first and second lens arrays.
With this construction, since the polarization changing optical system is arranged between the first and second lens arrays constructing an optical integrator, it can be installed in a space for the optical integrator. Accordingly, there can be obtained the liquid crystal projector provided with the illumination optical system in which the polarization changing optical system and the optical integrator are installed in a smaller space.
According to another aspect of the present invention, a liquid crystal projector comprising: a liquid crystal panel; an illumination optical system for illuminating the liquid crystal panel, the illumination optical system including: a light source which emits a beam of light; a first lens array and a second lens array arranged in this order from the light source, the first and second lens arrays each having a plurality of lenses; and a polarization changing optical system arranged more toward the liquid crystal panel than the first lens array.
With this construction, since the polarization changing optical system is distanced from the light source by being arranged more toward the liquid crystal panel of the optical integrator, thus eliminating the likelihood that the polarization changing optical system is degraded by heat from the light source.
According to still another aspect of the present invention, a liquid crystal projector comprising: a liquid crystal panel; an illumination optical system for illuminating the liquid crystal panel, the illumination optical system including: a light source which emits a beam of light; a first lens array and a second lens array arranged in this order from the light source, the first and second lens arrays each having a plurality of lenses; a half-wave plate arranged in the vicinity of the second lens array; and a polarization changing optical system arranged more toward the light source than the second lens array.
With this construction, the polarization changing optical system is arranged more toward the light source than the second lens array. Accordingly, polarization change can be performed in a smaller space in the direction normal to the optical axis of the illumination optical system. The size of the illumination optical system can be reduced.
Further, the polarization changing optical system may be arranged more toward the liquid crystal panel than the first lens array. The second lens array may be preferably provided with twice as many lenses as the first lens array. The polarization changing optical system may be preferably provided with a polarized beam splitting surface and a full reflection surface. Further, the polarization changing optical system may be preferably made of a material having a property of birefringence.
These and other objects, features and advantages of the present invention will become more apparent upon a reading of the following detailed description and accompanying drawings.
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patent: 5550656 (1996-08-01), Sprague et al.
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patent: 5726719 (1998-03-01), Tanaka et al.
patent: 5729306 (1998-03-01), Miayake et al.
patent: 5808800 (1998-09-01), Handschy et al.
patent: 5856479 (1998-12-01), Ueda et al.
patent: 5898521 (1999-04-01), Okada
patent: 6-110079 (1994-04-01), None
patent: 6-265887 (1994-09-01), None
patent: 7-120753 (1995-05-01), None
Mushiake Nobuo
Nagata Hideki
Ohta Takashi
Ohzawa Soh
Sawai Yasumasa
Burns Doane , Swecker, Mathis LLP
Minolta Co. , Ltd.
Ton Toan
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