Liquid crystal cells – elements and systems – Liquid crystal system – Projector including liquid crystal cell
Reexamination Certificate
2001-05-15
2003-09-30
Parker, Kenneth (Department: 2871)
Liquid crystal cells, elements and systems
Liquid crystal system
Projector including liquid crystal cell
C353S034000
Reexamination Certificate
active
06628346
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a reflection liquid crystal projector designed so that a colored image, which are synthesized from the images of a first, a second and a third colors (e.g., R, B and G lights) formed on a first, a second and a third panels (e.g., reflection panels for R, B and G) respectively, can be projected on a screen through a projection lens.
BACKGROUND ART
Conventionally, it has been a common practice that a reflection liquid crystal projector has a composition as is shown in FIG.
1
. That is, the white light outputted from a light source
10
is converted into an S-polarized light by a polarized light conversion element
12
; of the S-polarized light, the R light (Red light) is separated from the B light (Blue light) and G light (Green light) by a cross dichroic mirror
14
; the B and G lights are led to the dichroic mirror
18
by means of a cross dichroic mirror
14
; the B and G lights are led to the dichroic mirror
18
by means of a total reflection mirror
16
to be separated into the B light and G light.
The separated R light is led to a first polarization beam splitter
22
(hereinafter referred to the first PBS) by a total reflection mirror
20
; the R light is reflected by the polarizing film of the first PBS to fall on a reflection liquid crystal panel
24
(hereinafter referred to as the LCD for R), and the reflected light (converted into a P-polarized light from an S-polarized light) is outputted through the splitter
22
.
The separated B light is reflected by the polarizing film of a second polarization beam splitter
26
(hereinafter referred to as the second PBS) to fall on a reflection liquid crystal panel
28
(hereinafter referred to as the LCD for B), the panel being provided for the display of B image, and the reflected light (converted to P-polarized light from the S-polarized light) is outputted through the beam splitter
26
.
The separated G light is reflected by the polarizing film of a third polarization beam splitter
30
(hereinafter referred to the third PBS) to fall on a reflection liquid crystal panel
32
(hereinafter referred to as the LCD for G), the panel being provided for the display of a G image, and the reflected light (converted to P-polarized light from S-polarized light) is outputted passing through the beam splitter
30
.
A cross prism
34
not only reflects the R and B lights, outputted from the first and the second PBS's
22
and
26
, but also passes the G light outputted from the third PBS
30
to synthesize the R, B and G lights to display a colored image by projecting the synthesized light on a screen (not shown) through a projection lens
36
.
However, such a conventional method shown in
FIG. 1
has problems as are given below.
(1) Using an expensive cross prism
34
as a color synthesizing element results in the high price of a projector. More specifically, using the cross prism, which is to be assembled with four parts, results in low yield, high price and increase in weight of the projector.
(2) Needing 3 PBS's, i.e., the first PBS
22
, the second PBS
26
and the third PBS
30
, contributes not only to a high cost but also an increase in weight.
The present invention is made in consideration of the above-mentioned problems and is intended to provide a low-price and lightweight reflection liquid crystal projector by eliminating the costly cross prism and decreasing the required number of polarization beam splitters.
DISCLOSURE OF THE INVENTION
The present invention relates to a reflection liquid crystal projector designed for displaying a colored image, through a projector, on a screen by synthesizing a first, a second and a third color light (e.g., R, B and G lights) produced on a first, a second and a third reflection liquid crystal panel (e.g., LCD's for R, B and G), the projector comprising a light source for outputting a white light, a polarized light conversion element for converting the white light outputted from the light source into either a P-polarized light or a S-polarized light for output, a color separation element for not only separating the polarized light outputted from the polarized light conversion element into the first, the second and the third colored lights but also for outputting the two color lights (e.g., B and G lights), differing in the direction of polarization but traveling in the same direction, out of the first, the second and the third color lights, while outputting the remaining one color light (e.g., R light) in a direction perpendicular to the direction of the two color lights (e.g., B and G lights), a first polarized beam splitter for not only permitting one (e.g., G light) of the two color lights to pass through but also reflecting the other (e.g., B light) to fall on corresponding reflection liquid crystal panels (e.g., LCD's for G and B) for being outputted as reflected lights, a second polarization beam splitter for letting one colored light, the remainder of the color lights outputted from the color separation element falling on a corresponding one (e.g., LCD for R) of the first, the second and the third reflection liquid crystal panels so that the light can be outputted as a reflected light, and a dichroic prism for synthesizing the first, the second and the third color lights, outputted from the first and the second polarized beam splitters, for output to the projection lens.
In such a composition, the white light outputted from the light source by means of the polarized light conversion element is converted into either one (e.g., S-polarized light) of the S-polarized light or the P-polarized light; the polarized light is separated into the first, the second and the third color lights by the color separation element; the two color lights (e.g., B and G lights), differing in the direction of the polarization, out of the first, the second and the third color lights, are outputted in the same direction, while the remaining one color light,(e.g., R light) is outputted in a direction perpendicular to the output direction of the two color lights (e.g., B and G lights). The two color lights (e.g., G and B lights) outputted in the same direction from the color separation element are made to fall on corresponding reflection liquid crystal panels (e.g., LCD for G and B) by means of the first polarized beam splitter so that the reflected lights are outputted to the dichroic prism. The remaining one color light (e.g., R light), separated by the color separation element is made, by the second polarized beam splitter, to fall on a corresponding reflection liquid crystal panel (e.g., LCD for R) so that the reflected light is outputted to the dichroic prism. The dichroic prism synthesizes the first, the second and the third color lights outputted from the first and the second polarization beam splitters, and the synthesized light is projected, through the projection lens, to display the colored image on a screen.
Therefore, in the case of the present invention, not only the 3 sets of the polarized beam splitters necessary for the conventional projector can be reduced to 2 sets but also the costly cross prism as a color synthesizing element can be omitted, contributing to the realization of a low-price and lightweight projector.
In order to simplify the composition of the color separation element, the color separation element is made to comprise a first and a second dichroic mirror and a first and a second total reflection mirror. Of the polarized lights outputted from the polarized light conversion element, the first and the second color lights are allowed to pass through the first dichroic mirror while the third color light is reflected thereby. The first and the second color lights, which have passed through the first dichroic mirror, are reflected by the first total reflection mirror in a direction bent by 90°, while the third color light, reflected by the first dichroic mirror, is reflected by the second total reflection mirror in a direction bent by 90°; the second dichroic mirror not only permits one of the firs
Flynn ,Thiel, Boutell & Tanis, P.C.
Fujitsu General Limited
Parker Kenneth
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