Optics: image projectors – Composite projected image – Multicolor picture
Reexamination Certificate
2002-03-04
2004-04-06
Adams, Russell (Department: 2851)
Optics: image projectors
Composite projected image
Multicolor picture
C353S020000, C353S033000, C353S081000, C353S122000, C349S005000, C349S007000, C349S009000, C348S744000
Reexamination Certificate
active
06715882
ABSTRACT:
This application claims the benefit of Japanese Patent application No. 2001-062115 which is hereby incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a projection type display device constructed in a way that modulates and reflects color beams entering reflection type light valves disposed for a R (Red)-beam, a G (Green)-beam and a B (Blue)-beam and lets these beams exit, synthesizes and analyzes these color beams, and projects the color beam through a projection lens.
2. Related Background Art
An example of a construction of a prior art projection type display device will be explained. To begin with, a substantially parallel beam from a light source is polarization-split by a polarization beam splitter. Next, the thus polarization-split beam is color-separated into the R (Red)-beam, the G (Green)-beam and the B (Blue)-beam by a color separating optical system. The color-separated color beams such as the R-beam, G-beam and B-beam enter the light valves for the R-, G- and B-beams. The respective color light valves modulate the incidence beams in accordance with image signals and let the modulated beams exit. The reflected beams modulated by the light valves are color-synthesized by a color synthesizing optical system. Then, the color-synthesized beam reenter the polarization beam splitter and is analyzed. Finally, the analyzed beam exiting the polarization beam splitter is projected as a full-color image of the modulated image on a screen through a projection lens.
FIG. 11
is a view schematically showing a configuration of the projection type display device in the prior art and light paths therein. A light source
1
constructed of a lamp and a concave surface mirror such as a parabolic mirror, emits substantially parallel light source beam. The light source beam from the light source
1
enters a fly's eye integrator FE. The fly's eye integrator FE is constructed of a first lens plate
2
having a plurality of first lens elements
2
a
,
2
b
,
2
c
, and a second lens plate
3
having a plurality of second lens elements
3
a
,
3
b
,
3
c
corresponding to the first lens elements
2
a
,
2
b
,
2
c
. Herein, the second element elements
3
a
,
3
b
,
3
c
are provided in focal positions of the first lens elements
2
a
,
2
b
,
2
c
. With this construction, the beam from the light source
1
is, after being split, overlapped on the light receiving surfaces of light valves defined as the radiation receiving surfaces. A uniformity of illuminance of the illumination radiation can be thereby enhanced.
The beams exiting the fly's eye integrator FE enter the polarization beam splitter
6
via a condenser lens
4
and a field lens
5
. A polarized light splitting element
6
P of the polarization beam splitter
6
reflects an S-polarized beam and transmits a P-polarized beam, thus polarization-splitting the beams. The S-polarized beam reflected by the polarized light splitting element
6
P is discarded as an unnecessary beam.
The P-polarized beam exiting the polarization beam splitter
6
enters a color separating/synthesizing composite prism constructed of prisms
7
,
8
and
9
. The color separating/synthesizing composite prism color-separates the light source beam into the B-, R and G-beams. The structure for the color separation is the same as what is disclosed in, e.g., Patent Publication No. 2505758, and therefore its repetitive explanation is herein omitted.
The color-separated beams assuming the respective colors are incident on light valves
10
B,
10
R,
10
G for the respective colors. The color light valves
10
B,
10
R,
10
G modulate the incidence beams in accordance with image data and then let the modulated beams exit. The beams exiting the color light valves
10
B,
10
R,
10
G enter the color separating/synthesizing composite prism and are color-synthesized. The thus color-synthesized beam enters the polarization beam splitter
6
. The polarized-light splitting element
6
P of the polarization beam splitter
6
reflects and analyzes the modulated beam (S-polarized beam) in the color-synthesized beam. The modulated beam reflected by the polarized-light splitting element
6
P exits the polarization beam splitter
6
. The modulated beam exiting the polarization beam splitter
6
enters a projection lens
11
. The projection lens
11
projects images generated on the color light valves
10
B,
10
R,
10
G as a full-color image on a screen
12
.
In the projection type display device according to the prior art, light is absorbed by glass materials constituting the polarization beam splitter
6
, and the prisms
7
,
8
,
9
of the color separating/synthesizing composite prism, a bonding agent for bonding the prisms to each other and an optical thin film for color-separating the incidence beams. With this light absorption, the polarization beam splitter
6
, the prisms
7
,
8
,
9
get exothermic. With this heat emission, volumes of the optical elements expand. Herein, the optical elements such as the polarization beam splitter
6
and the prisms
7
,
8
,
9
are mechanically fixed to a frame or the like. Accordingly, stresses derived from the heat emission occur in interiors of the optical elements. Then, a polarized-light splitting characteristic declines due to these stresses. This results in such a problem that a contrast of the projected image decreases.
A relationship between the stresses derived from the heat emission and configurations of the light paths or the optical elements, will be explained in greater detail.
Referring to
FIG. 11
, the beams converged on the lens elements
3
a
,
3
c
of the second lens plate
3
that correspond to the outermost lens elements
2
a
,
2
c
of the first lens plate
2
receiving the incidence of the light source beams, form luminous points. Outermost marginal rays i
1
, i
2
of the beams emerging from these luminous points travel through the condenser lens
4
and the field lens
5
. Then, the two rays i
1
, i
2
become the outermost marginal rays of the beam entering the polarization beam splitter
6
.
Further, the light source beam traveling via the lens element
2
b
of the first lens plate
2
on an optical axis I is converged as a luminous point on the corresponding lens element
3
b
of the second lens plate
3
. The beam from this luminous point on the second lens plate
3
becomes chief rays i
0
. The field lens
5
collimates the chief rays i
0
into substantially parallel light rays. Then, the chief rays collimated into substantially the parallel light rays travel through the prisms
7
,
8
,
9
of the color separating/synthesizing composite prism and the color light valves
10
B,
10
R,
10
G and are converged at an aperture stop (unillustrated) of the projection lens
11
.
A size of each of incidence surfaces of the light valves
10
B,
10
R,
10
G is 0.907 in., and a surface dimension of the incidence surface is given by 18.43 mm (width)×13.82 mm (length). In
FIG. 11
showing the schematic geometry, a long side of the incidence surface of each of the light valves
10
B,
10
R,
10
G is parallel with the sheet surface, while the short side is vertical to the sheet surface. This geometry will hereinafter be called a “lateral layout”.
FIG. 12A
is a view showing a configuration in section perpendicular to the light source beam incidence surface
7
a
of the prism
7
. The outermost marginal ray i
1
enters, from the side of the surface
7
a
, the vicinity of an acute-angled &agr; portion formed of the incidence surfaces
7
a
,
7
b
of the prism
7
taking substantially a shape of a triangular prism.
FIG. 12B
is a view viewed from the side of the surface
7
a
of the prism
7
.
FIG. 12C
is a view viewed from the side of the surface
7
c
of the prism
7
. The B-beam in the beam entering the surface
7
a
is reflected by the surface
7
b
coated with the dichroic film reflecting the B-beam. Next, the B-beam is totally reflected by the surface
7
a
and thereafter exits the surface
7
c
. Therefore, as shown in
FIG. 12B
, an eff
Adams Russell
Koval Melissa
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