Liquid crystal cells – elements and systems – Liquid crystal system – Projector including liquid crystal cell
Reexamination Certificate
1999-10-05
2001-08-21
Dudek, James A. (Department: 2871)
Liquid crystal cells, elements and systems
Liquid crystal system
Projector including liquid crystal cell
C349S008000, C349S095000
Reexamination Certificate
active
06278500
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of Invention
This invention relates to a liquid crystal device and to a projection display device using the liquid crystal device.
2. Description of Related Art
A projection display device can be used to display a computer image and a television image. The projection display device modulates a light beam emitted from a light source with an electro-optical device called a light valve, and projects the modulated light beam onto a screen to display an image. A liquid crystal device is usually used as the light valve of such a projection display device.
The projection display device is usually provided with a cooling fan, and the liquid crystal device is cooled by a flow of air generated by the cooling fan. However, since dust is often included in air, the dust may adhere to the surface of the liquid crystal device. When the dust adheres to the surface of the liquid crystal device, a shadow of the adhered dust is projected, such that the quality of an image displayed by the projection display device is deteriorated.
SUMMARY OF THE INVENTION
This invention is directed to solving the above-described problems in the conventional art, and an object of the invention is to provide a technique preventing the deterioration of image quality, even if the dust adheres to the surface of the liquid crystal device.
In order to solve the above-described problems, a projection display device of the present invention includes:
a liquid crystal device, having a plurality of pixels, that modulates and emits a light beam according to a given image signal;
an illuminating optical system that provides a light beam to the liquid crystal device; and
a projection optical system that projects an image light beam emitted from the liquid crystal device to project an image onto a screen;
wherein the liquid crystal device includes an emergent-side substrate section, an incident-side substrate section disposed opposing the emergent-side substrate section; and a liquid crystal layer disposed between the emergent-side substrate section and the incident-side substrate section;
wherein the incident-side substrate section includes an incident-side substrate, an electrode that drives the liquid crystal layer formed on the incident-side substrate, and a micro-lens array disposed toward an incident side of the liquid crystal device relative to the incident-side substrate and having a plurality of micro-lenses that condense light beams into a plurality of pixels; and
wherein a thickness Ti of the incident-side substrate section along a direction of travel of a light beam is larger than a thickness To of the emergent-side substrate section along the direction of travel of the light beam.
In accordance with this structure, the light beam condensed by the micro-lens enters the liquid crystal layer, so that the light beam emitted from the liquid crystal layer is diffused by the action of the micro-lens. In this case, the divergence of the light beam emitted from the liquid crystal device is larger than that of a liquid crystal device having no micro-lens, so that the influence of the dust on the emergent plane of the liquid crystal device is reduced. Therefore, as compared with the influence of the dust on the emergent plane of the liquid crystal device, the influence of the dust on the incident plane of the liquid crystal device tends to be relatively great. If the above arrangement is employed, the influence of the dust adhering to the side of the incident plane of the liquid crystal device can be reduced in such a manner as to come close to the influence of the dust adhering to the side of the emergent plane of the liquid crystal device, because the plane on the incident side of the liquid crystal device is located at a position further away from the liquid crystal layer than the plane on the emergent side.
In the above arrangement, the incident-side substrate section may further include an incident side-glass plate provided toward the incident side of the liquid crystal device relative to the micro-lens array;
the emergent-side substrate section may preferably include an emergent-side substrate, an electrode that drives the liquid crystal layer formed on the emergent-side substrate, and an emergent-side glass plate provided toward an emergent side of the liquid crystal device relative to the emergent-side substrate; and
a thickness of the incident-side glass plate and the emergent-side glass plate may preferably be set in such a manner that the thickness Ti of the incident-side substrate section is larger than the thickness To of the emergent-side substrate section.
With the above arrangement, the thickness Ti and To of the incident-side substrate section and the emergent-side substrate section can be easily adjusted by adjusting the thickness of the incident-side glass plate and the emergent-side glass plate.
In each of the above cases, if F-numbers of the illuminating optical system and the projection optical system are taken as F
L
and F
P
, respectively, the thickness Ti and the thickness To may preferably satisfy the relationship Ti≈To×(F
L
/F
P
).
With the above arrangement, the influence of the dust adhering to the incident side of the liquid crystal device can be made substantially equal to the influence of the dust adhering to the emergent side of the liquid crystal device.
Incidentally, of the optical elements that are included in the illuminating optical system, the F-number of an optical element disposed on the lowermost side of an optical path may be used as the F-number F
L
.
In this case, the illuminating optical system may include:
a light source;
a dividing optical system that divides a light beam emitted from the light source into a plurality of partial light beam fluxes; and
a superimposing optical system having the function of substantially superimposing the plurality of partial light beam fluxes on the liquid crystal device, wherein the F-number of the superimposing optical system is used as the F-number F
L
.
In addition, the illuminating optical system may include:
a light source;
a first lens array having a plurality of first small lenses that divide a light beam emitted from the light source into a plurality of partial light beam fluxes; and
a second lens array having a plurality of second small lenses corresponding to the plurality of first small lenses, wherein the F-number of the second lens array may be used as the F-number F
L
.
Furthermore, the illuminating optical system may include:
a light source;
a first lens array having a plurality of first small lenses that divide a light beam emitted from the light source into a plurality of partial light beam fluxes;
a second lens array having a plurality of second small lenses corresponding to the plurality of first small lenses; and
a superimposing lens that substantially superimposes a plurality of partial light beam fluxes emitted from the second lens array on said liquid crystal device; wherein the F-number of the superimposing lens may be used as said F-number F
L
.
Even if each of the above-described illuminating optical systems is employed, the influence of the dust adhering to the incident side of the liquid crystal device can be made substantially equal to the influence of the dust adhering to the emergent side of the liquid crystal device.
In each of the above cases, the projection display device may include:
a color-light-beam-separating optical system that separates a light beam emitted from the illuminating optical system into a plurality of color light beams;
a plurality of the liquid crystal devices that modulates and emits color light beams separated by the color-light-beam-separating optical system;
a color-light-beam-synthesizing optical system that synthesizes the color light beams emitted from the plurality of liquid crystal devices; and
a projection optical system that emits and projects a light beam synthesized by the color-light-beam synthesizing optical system.
A liquid crystal device of the present invention includes:
an emergent-side substrate section; an incident-side subs
Ogawa Yasunori
Takizawa Takeshi
Yajima Akitaka
Dudek James A.
Oliff & Berridg,e PLC
Qi Mike
Seiko Epson Corporation
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