Optical: systems and elements – Optical modulator – Light wave temporal modulation
Reexamination Certificate
1999-05-11
2002-04-16
Mai, Huy (Department: 2873)
Optical: systems and elements
Optical modulator
Light wave temporal modulation
C349S110000, C349S153000
Reexamination Certificate
active
06373616
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical modulation device having an electrooptical device, such as a liquid crystal panel, and to a projection display device using this optical modulation device.
2. Description of the Related Art
A liquid crystal panel that serves as an electrooptical device for use in a projection display device generally comprises an active matrix substrate having pixel electrodes and pixel switching elements, an opposite substrate having opposite electrodes, and liquid crystal interposed between the active matrix substrate and the opposite substrate. The liquid crystal is filled in a region partitioned by a sealing layer out of the space between the active matrix substrate and the opposite substrate, and the alignment state thereof is controlled pixel by pixel between the active matrix substrate and the opposite substrate.
Therefore, in a projection display device using the liquid crystal panel having such a structure as an optical modulation device, light emitted from a light source is collected and guided to the liquid crystal panel by a light-collecting optical system, and this light is optically modulated by the liquid crystal, whereby a predetermined image is enlarged and projected onto a projection plane, such as a screen, by a projection lens.
The liquid crystal panel structured as mentioned above is usually held by a light-shielding holding member having an open portion corresponding to an image area. In general, the image area is outlined by a light shielding portion of Cr (chrome) that is formed between the active matrix substrate and the opposite substrate to define the periphery.
On the light-incident side of the liquid crystal panel, however, since a cover portion that forms a peripheral edge of the open portion of the holding member faces the light-incident surface of the liquid crystal panel (opposite substrate) and overlaps with the light-shielding portion in a planar manner, light that is incident from the outside of the inner peripheral edge of the cover portion is blocked by the cover portion depending on the incident angle. Therefore, the peripheral portion of a projection image becomes dark, and this may deteriorate the quality of the projection image.
SUMMARY OF THE INVENTION
An object of the present invention is to provide an optical modulation device that is able to improve the quality of a projection image, and a projection display device using this optical modulation device.
An optical modulation device of the present invention includes an electrooptical device having a first light-transmissive substrate disposed on the light-incident side, a second light-transmissive substrate disposed on the light-emitting side, liquid crystal interposed between opposing surfaces of these first and second light-transmissive substrates, and a driving circuit disposed at the peripheral edge of a light-incident surface of the second light-transmissive substrate, and a holding member for holding the electrooptical device, wherein a first light-shielding portion for defining an image area is formed between the first and second light-transmissive substrates in the electrooptical device, a cover portion for covering the peripheral edge of a light-incident surface of the first light-transmissive substrate is formed in the holding member, and Wp and W
1
are set in a relationship that is expressed by the following equation (1):
Wp<W
1
(1)
where Wp is the distance from the end of the first light-transmissive substrate to the inner peripheral edge of the cover portion in the holding member, and W
1
is the distance from the end of the first light-transmissive substrate to the inner peripheral edge of the first light-shielding portion.
Herein, “the inner peripheral edge of the cover portion” means a part of the cover portion that projects toward the image area to the largest degree and that is most apart from the light-incident surface of the first light-transmissive substrate. Furthermore, “the distance from the end of the first light-transmissive substrate” means the distance along the in-plane direction of the first light-transmissive substrate.
In the present invention configured like this, since the distance Wp from the end of the first light-transmissive substrate to the inner peripheral edge of the cover portion is set to be smaller than the distance W
1
from the end of the first light-transmissive substrate to the inner peripheral edge of the first light-shielding portion, there is no fear that the inner peripheral edge of the cover portion may project into the image area beyond the first light-shielding portion. Since incident light that is incident from the outside of the inner peripheral edge of the cover portion reliably enters the entire image area without being blocked by the cover portion, the peripheral portion of a projection image does not become dark, and the quality of the projection image is thereby improved.
In the optical modulation device of the present invention, when the incident angle of incident light, which is incident from the inside of the inner peripheral edge of the cover portion, of light that is incident on the electrooptical device, is &thgr;i, the incident angle of incident light, which is incident from the outside of the inner peripheral edge of the cover portion, is &thgr;o, the distance from the inner peripheral edge of the cover portion to the light-incident surface of the first light-transmissive substrate is dp, the thickness of the first light-transmissive substrate is d
1
, the distance from the end of the first light-transmissive substrate to the outer peripheral edge of the first light-shielding portion is W
1
′, and the refractive index of the first light-transmissive substrate is n
1
, it is preferable to set Wp, W
1
, and W
1
′ in a relationship expressed by the following equation (2).
W1
′
+
dp
tan
θ
i
+
d1
sin
θ
i
n1
2
-
sin
2
θ
i
≤
Wp
≤
W1
-
dp
tan
θ
o
-
d1
sin
θ
o
n1
2
-
sin
2
θ
o
(
2
)
When the first light-transmissive substrate and the second light-transmissive substrate are bonded with a sealing material of an ultraviolet-curing type, there is a need to leave a light-transmissive portion of the first light-transmissive substrate outside the first light-shielding portion. Since the first light-transmissive substrate has the thickness d
1
, incident light that is incident from the inside of the inner peripheral edge of the cover portion is, in some cases, not entirely blocked by the cover portion of the holding member according to the incident angle, passes through the light-transmissive portion of the first light-transmissive substrate, and leaks from the outer peripheral edge of the first light-shielding portion. For this reason, the leaking incident light impinges on a driving circuit that is disposed on the periphery of the second light-transmissive substrate, thereby causing a malfunction of the driving circuit. When the distance Wp is set within the range given by the equation (2), however, there is no fear that the quality of a projection image may be deteriorated by incident light that is incident from the outside at the incident angle &thgr;o. Moreover, there is no fear that incident light incident from the inside at the incident angle &thgr;i may leak from the outer peripheral edge of the first light-shielding portion, and that the light may be applied onto the driving circuit disposed on the periphery of the second light-transmissive substrate. Therefore, even when a light-transmissive portion is formed outside the first light-shielding portion, the driving circuit is prevented from malfunctioning.
Furthermore, in the optical modulation device of the present invention, it is preferable to form a third light-transmi
Ogawa Yasunori
Saito Hiromi
Toda Shigeo
Watanabe Nobuo
Mai Huy
Seiko Epson Corporation
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