Optics: image projectors – Polarizer or interference filter
Reexamination Certificate
2003-08-28
2004-12-28
Nguyen, Judy (Department: 2851)
Optics: image projectors
Polarizer or interference filter
C353S038000, C353S084000, C353S102000, C359S483010, C359S577000, C359S892000
Reexamination Certificate
active
06834962
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a projection system that can be applied to a projection TV or a projection monitor, and more particularly, to a projection system that can improve a contrast while maintaining a proper brightness of a set to which the projection system is applied.
2. Description of the Related Art
An optical system that is employed to a projection TV or a projection monitor is generally comprised of a polarization converting part for converting light that is irradiated from a light source lamp and has an irregular polarization direction (the light source will be referred as “irregular polarization light flux” hereinafter) into a plurality of polarization light fluxes having an identical single polarization direction, and a color separating part for separating the polarization light fluxes, which are irradiated from the polarization converting part with the single polarization direction, by colors.
FIG. 1
shows a detailed view of a polarization converting part of a conventional optical system.
As shown in
FIG. 1
, a polarization converting part includes a light source part
10
comprised of a light source lamp
11
and a parabolic reflector
12
and a polarization generating part
20
comprised of a first optical element
30
and a second optical element
40
.
In addition, the first optical element
30
includes a plurality of light flux dividing lenses
31
shaped in a rectangular are arranged in a matrix configuration, and the second optical element
40
is formed in a complex member comprised of a condenser lens array
41
, a light shielding plate
44
, a polarization separating unit array
43
, a selective phase difference plate
45
, and a coupling lens
46
.
The coupling lens
46
can be separated for convenience.
In the polarization converting part constructed as above, the irregular polarization light flux that is incident from the light source part
10
to the first optical element
30
is divided into a plurality of intermediate light fluxes by the light flux dividing lenses
31
.
The divided intermediate light fluxes are spatially separated in a P-polarization light flux space and an S-polarization space by the polarization separating unit array
43
. And then, the spatially separated polarization directions are coincided in an identical single polarization direction by the selective phase difference plate
45
. The coincided polarization light fluxes are induced toward a panel
50
through the coupling lens
46
.
The coincided polarization light fluxes generated from the polarization converting part is separated by colors while passing through a reflection or transmission filter of the color separation part.
FIGS. 2 and 3
show a detailed view of a conventional color separation part.
FIG. 2
illustrates a transmissive LCD. As light flux emitted from the polarization generating part
20
is incident into a red light reflection mirror
71
of the color and light separation means, blue and green lights are transmitted but red light is reflected on the red light reflection mirror
71
. The reflected red light is reflected by a downstream reflection mirror
72
to reach a red light liquid crystal part
51
.
Meanwhile, as the blue and green lights transmitted through the red light reflection mirror
71
are again incident into a green light reflection mirror
73
, the green light is reflected and the blue light is transmitted.
The reflected green light reaches the green light liquid crystal part
52
, and the blue light transmitted through the green light reflection mirror
73
is reflected by a downstream blue light reflection mirror
74
.
The reflected blue light is reflected by the downstream reflection mirror
75
to reach the blue light liquid crystal part
53
.
The three liquid crystal parts
51
,
52
and
53
modulate each of the color lights. The modulated color lights containing image information corresponding to the color lights is incident to color lights synthesizing means such as a cross dichroic prism
60
. The cross-dichroic prism
60
forms a color image by synthesizing the modulated fluxes to form a color image. The color image is projected to a screen
80
by a projection lens
70
defining a projection optical system, thereby forming a projected color image.
FIG. 3
illustrates a reflective LCD. As light flux emitted from the polarization generating part
20
is incident into a blue light reflection mirror
76
of the color and light separation means, red and green lights are transmitted but blue light is reflected by the blue light reflection mirror
76
.
The reflected blue light is reflected by a downstream reflection mirror
78
and then reflected by a downstream blue light filter
94
to reach a blue light liquid crystal part
56
, and is then shifted in its phase by 90°. After that, the phase-shifted light is incident into a cross dichroic prism
60
through the blue light filter
94
.
Meanwhile, as the red and green lights transmitted through the green light reflection mirror
77
are incident into the green light reflection mirror
77
of the color and light separating means, the green light is reflected by the green light reflection mirror
77
and the red light is transmitted.
The reflected green light is reflected by the green light filter
92
to reach a green light liquid crystal part
55
, and is then phase-shifted by 90°. After that, the phase-shifted light is incident to the cross dichroic prism
60
through the green light filter
92
.
The red light transmitted through the green light reflection mirror
77
is reflected by a red light filter
90
to reach a red light liquid crystal part
54
, and is then phase-shifted by 90° through the red light liquid crystal part. After that, the phase-shifted light is incident to the diachronic prism
60
via the red light filter
90
.
The cross-dichroic prism
60
synthesizes the modulated light fluxes to form a color image. The color image formed by the cross-dichroic prism
60
is projected onto a screen
80
by a projection lens
70
, which is a kind of a projection optical system, thereby forming a projected color image.
The above-described optical system can be classified into a single plate type, a dual plate type, and a triple plate type depending on the number of the liquid crystal parts that are a display device. The optical systems depicted in
FIGS. 2 and 3
are exampled as the triple optical system.
However, the above-described optical system has a problem in that the brightness and the contrast are oppositely related with each other. That is, when the contrast is increased, the brightness is reduced, whereas when the brightness is increased, the contrast is reduced.
SUMMARY OF THE INVENTION
Accordingly, the present invention is directed to a projection system that substantially obviates one or more problems due to limitations and disadvantages of the related art.
An object of the present invention is to provide a projection system that can improve a contrast while maintaining a proper brightness of a set to which the projection system is applied.
Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objectives and other advantages of the invention may be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
To achieve these objects and other advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, there is provided a projection system comprising a polarization converting part for converting an incident polarization light flux into a polarization light flux having one direction, and a color separating part for color-separating the polarization light flux irradiated from the polarization converting part, the polarization converting part comprising: an FEL
Koval Melissa J
Nguyen Judy
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