Liquid crystal cells – elements and systems – Particular structure – Particular illumination
Reexamination Certificate
2002-03-18
2004-03-16
Palmer, Phan T. H. (Department: 2874)
Liquid crystal cells, elements and systems
Particular structure
Particular illumination
C349S064000, C349S008000, C385S016000, C385S024000, C359S634000
Reexamination Certificate
active
06707514
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATION
This application claims the priority benefit of Japanese application serial no. 2001-081267, filed on Mar. 21, 2001 and 2001-187577, filed on Jun. 21, 2001.
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates in general to an optical path element, an optical switching element, a spatial light modulator and an image display apparatus. More specifically, the invention relates to an optical path element, an optical switching element and a spatial light modulator, and an image display apparatus using the above, by which simpler structure, superior durability, low device cost, and high utilization rate for light can be achieved.
2. Description of Related Art
An optical switching device is used for switching the light by changing the reflection direction of an incident light. For example, Japanese Laid Open H05-196880 discloses an optical switching device and a spatial light modulator using the optical switching device, in which a plurality of tiny rotational mirrors are arranged in a two dimensional array.
FIG. 19
shows a plane view of a conventional spatial light modulator disclosed in Japanese Laid Open H05-196880. As shown, only a torsion beam reflection surface
11
and a beam supporting post
12
are observed.
FIGS. 20A and 20B
show a cross-sectional view of one of rotational mirrors of the spatial light modulator in FIG.
19
.
FIG. 20A
is a cross-sectional view along a hinge and
FIG. 20B
is a cross-sectional view perpendicular to FIG.
20
A. The beam
11
can be rotated around a ground electrode
14
by the beam supporting post
12
due to the twist of the hinge
13
connected to the post
15
. The driving force is given by applying a voltage to an address electrode
17
supported by the post
16
. The voltage applied to the address electrode
17
is by transmitting a signal through a metal layer
18
, in which the signal is from a CMOS circuit (not shown) formed on a substrate
19
. The rotational status of the beam
11
varies for each rotational mirror so that the incident light can be spatially modulated in a two-dimensional manner.
According to the above structure, in order to obtain a large rotational angle, the structure of the rotational mirror becomes very complicated and the manufacturing cost increases.
Japanese Laid Open H11-202222 discloses another exemplary optical switching device, the operation of which is explained in FIG.
21
. The optical switching device comprises a light transmission part
21
provided with a full reflecting plane
22
for fully reflecting light and transmitting it, a prism
31
capable of capturing, reflecting and emitting evanescent light while an extracting plane
32
is near the full reflecting plane
22
, and a driving part
40
for driving the prism
31
, which are all laminated in this order in the light emitting direction. The cell at the right side shown in
FIG. 21
activates the driving part
40
such that the prism
31
moves to a position above the extraction distance where the evanescent light would leak. At this time, as shown in
FIG. 21
, the light
1
transporting in the light transmitting element
21
is totally reflected at the total reflection surface
22
and then the reflected light
2
emits rightwards. When the driving part is deactivated, as in the cell at the left side shown in
FIG. 21
, because the prism
31
is near to a position under the extraction distance where the evanescent light would leak, the light I transporting in the light transmitting element
21
is not reflected at the total reflection surface
22
but enters the prism
31
. The light that enters the prism
31
is then reflected at the reflection surface
31
a
of the prism
31
and then passes through the light transmitting element
21
to emit as the light
3
shown in FIG.
21
.
According to the above method, the extracted and the unextracted states of the evanescent light can be switched. This structure is suitable for a tiny displacement about the wavelength of the light, and a simple driving mechanism can be used. However, because the mechanism of the prism
31
in
FIG. 21
is a very complicated structure, it is very difficult to form a plurality of tiny-size prisms on the substrate uniformly, causing problems such as low yield rate and high cost etc. Additionally, as the prism
31
approaches the total reflection surface
22
of the light transmitting element
21
, the Van der Walls force or the liquid bridging force occurs between them, and therefore it is very hard to separate the prism
31
from the total reflection surface
22
.
Japanese Laid Open 2000-171813 discloses another exemplary optical switching device, which is shown in
FIG. 22. A
light transmitting element for transmitting light by the total reflection is provided such that the alignment of a liquid crystal can be controlled by applying a voltage to the liquid crystal
60
that is in contact with the light transmitting element
50
. Therefore, the effective index of refraction can be varied with respect to an ordinary light and an extraordinary light. The switching mechanism can be made between the first state, where the incident light (linear polarized)
1
is emitted as a total reflection light
2
, and the second state, where the penetrated light of the incident light is reflected by a reflection film
61
to change its direction and then is emitted as a reflection light
3
. In
FIG. 22
, the light switching device further comprises a transparent electrode
51
, a driving IC for the liquid crystal
70
and electrode terminals
71
.
As described above, because there are no mechanical driving parts, the foregoing problems do not happen. However, because of the total reflection at the interface of the light transmitting element and the liquid crystal, it needs a material with a high index of refraction to make the light transmitting element, or a large incident angle is required, thereby the material cost becomes very high and the optical system is very complicated. Accordingly, it is not suitable for application in practice, because, for example, the light utilization rate is lowered.
SUMMARY OF THE INVENTION
To solve the aforementioned problems, the invention provides an optical path element, an optical switching element and a spatial light modulator, and an image display apparatus using the above, by which simpler structure, superior durability, low device cost, and high utilization rate for light can be achieved.
Therefore, it is an object of the invention to provide an optical switching element, which can be easily made at low cost.
It is another object of the invention to provide an optical switching element, which has a high S/N ratio and a small driving energy.
It is still another object of the invention to provide an optical switching element, which has a fast response time and a low light loss.
It is still another object of the invention to provide a spatial light modulator, of which the structure can be simplified, the durability is high, the cost can be reduced, and the light utilization rate can be increased.
It is still another object of the invention to provide a low-cost image display apparatus.
According to the foregoing description, an object of this invention is to provide an optical switching element, comprising: a first light transmitting element, having a first light incident surface, a second light incident surface that is not parallel to the first light incident surface, and a light outgoing surface; a reflection substrate, arranged opposite to the second light incident surface of the first light transmitting element and having a first reflection surface with a predetermined angle that is not parallel to the second light incident surface, wherein a reflected light passes through the first light transmitting element and the reflection substrate and then is reflected by the first reflection surface of the reflection substrate; and an index variable material, sandwiching between the first light transmitting element and the reflection substrate, which has an index of refraction
Kawashima Ikue
Kondoh Hitoshi
Tomono Hidenori
Dickstein , Shapiro, Morin & Oshinsky, LLP
Palmer Phan T. H.
Ricoh & Company, Ltd.
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