Optics: image projectors – Polarizer or interference filter
Reexamination Certificate
2001-12-17
2004-11-02
Dowling, William C. (Department: 2851)
Optics: image projectors
Polarizer or interference filter
C346S009000, C353S034000
Reexamination Certificate
active
06811261
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of Invention
The present invention relates to a projection display apparatus using a liquid crystal panel, and in particular relates to a liquid crystal projector having a polarization separator formed at the emitting side of the liquid crystal panel.
2. Description of Related Art
An exemplary related art liquid crystal projector is shown in FIG.
15
. The liquid crystal projector includes a light source
302
for emitting white light, a reflector
301
for making the white light emitted from the light source
302
substantially parallel, an incident side polarizing plate
303
for allowing an S wave in the reflected light from the reflector
301
, for example, to pass therethrough, a transmissive liquid crystal panel
304
for modulating the S wave which has passed through the incident side polarizing plate
303
corresponding to an image signal, an emitting side polarizing plate
305
disposed on the emitting side of the liquid crystal panel
304
for allowing only an arbitrary polarized element (S wave, for example) in the light transmitted from the liquid crystal panel
304
to pass therethrough, a projection lens
306
for magnifying and projecting the light transmitted from the emitting side polarizing plate
305
on a screen, and a cooling fan
307
for cooling the incident side polarizing plate
303
, the liquid crystal panel
304
, and the emitting side polarizing plate
305
.
In a liquid crystal projector
300
having the structure described above, when the S wave is transmitted from the incident side polarizing plate
303
, in a black region for example, the S wave is converted into a P wave in the liquid crystal panel
304
, while in a white region, the S wave is modulated so as to be transmitted. The converted P wave on one side is blocked off by the emitting side polarizing plate
305
to output a black color, and the S wave on the other side is transmitted to output a white color.
In the related art liquid crystal projector
300
mentioned above, because the emitting side polarizing plate
305
is an absorbing polarizing plate, when a polarized element (P wave, for example) perpendicularly intersecting a polarized element (S wave, for example), which passes through when outputting a black color, is absorbed, heat is generated. In particular, because the amount of light increases with increasing brightness of the liquid crystal projector, the absorbing polarizing plate may burn when outputting a black color over the entire region.
Furthermore, since heating the polarizing plate causes a material included in the polarizing plate, such as iodine, to randomly evaporate, the polarization becomes ununiform, resulting in a reduction of contrast, a generation of color phase irregularity, and a reduction in the polarizing plate life.
SUMMARY OF THE INVENTION
The present invention addresses this situation, and it is an object thereof to provide a projection display apparatus capable of reducing heat absorption of a polarizing plate.
In order to achieve the object mentioned above, according to the present invention, a projection display apparatus includes a light source that projects light onto an object to be projected; a polarizing unit that polarizes the light emitted from the light source at least in a first direction and a second direction that is different from the first direction; a color-separation unit that divides the light polarized by the polarizing unit into a plurality of colors; a plurality of liquid crystal panels that respectively modulate the plurality of colors divided by the color-separation unit; a color-combining unit that combine the plurality of colors respectively modulated by the plurality of liquid crystal panels so as to generate composite light including the plurality of colors; a polarization separator that separates first light rays, which are included in the composite light generated by the color-combining unit and polarized in the first direction by the polarizing unit, from second light rays, which are polarized in the second direction by the polarizing unit, by allowing the first light rays to pass therethrough while reflecting the second light rays therefrom; and a projecting unit that projects the first light rays separated by the polarization separator onto the object to be projected.
Furthermore, preferably, the polarization separator is arranged so that an angle of inclination of the polarization separator, which is the angle between the surface perpendicular to the direction of travel of the composite light generated by the color-combining unit and the polarization-separator surface on which the composite light enters, is an angle that results in a contrast that is larger than a contrast at which the angle of inclination is 0°, which is specified by characteristics defining the relationship between the angle of inclination of the polarization separator and the contrast which is the degree of separation to separate the first light rays from the second light rays.
REFERENCES:
patent: 5863125 (1999-01-01), Doany
patent: 6327093 (2001-12-01), Nakanishi et al.
patent: 6331060 (2001-12-01), Yamamoto et al.
patent: 6340230 (2002-01-01), Bryars et al.
patent: 6394606 (2002-05-01), Miyawaki et al.
patent: 6450645 (2002-09-01), Jeon
patent: 1253456 (2000-05-01), None
patent: 11-295660 (1999-10-01), None
Dowling William C.
Oliff & Berridg,e PLC
Seiko Epson Corporation
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