Liquid crystal cells – elements and systems – Particular structure – Having significant detail of cell structure only
Reexamination Certificate
2001-05-30
2004-08-31
Kim, Robert H. (Department: 2871)
Liquid crystal cells, elements and systems
Particular structure
Having significant detail of cell structure only
C349S119000
Reexamination Certificate
active
06784961
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a liquid crystal projector apparatus and more particularly to a liquid crystal projector apparatus adapted to prevent deterioration in contrast and uniformity due to properties of dependence on viewing angles.
2. Description of the Related Art
A projector apparatus for projecting an image on a screen under magnification and thus implementing a large screen is in widespread use as an image display apparatus for indoor and outdoor use. The projector apparatus is broadly divided into a projector apparatus (a CRT projector apparatus) for projecting exiting light from a fluorescent screen of a CRT onto a screen and a projector apparatus for projecting modulated light onto a screen after modulating light emitted from a light source by means of a spatial light modulator, and, in the case of the latter, a projector apparatus (a liquid crystal projector apparatus) using a liquid crystal panel as the spatial light modulator is in the mainstream.
FIG. 1
shows an example of a configuration of an optical system of a liquid crystal projector apparatus of the related art (an optical system of a three-panel transmission type liquid crystal projector apparatus using three transmission type liquid crystal panels for RGB).
A light source
11
includes a lamp
12
(e.g., a xenon lamp), and a reflector
13
for reflecting light (white unpolarized light) emitted from the lamp
12
so as to form the light into a bundle of rays having a predetermined angle of divergence. Light emitted from the light source
11
passes through microlens arrays
14
and
15
and a polarizer
16
in sequence.
The microlens arrays
14
and
15
comprise an array of a plurality of microlenses
14
a
and an array of a plurality of microlenses
15
a
, respectively (for example, each lens has a diameter of about 1 mm to 5 mm). Each lens
14
a
is rectangular and similar in shape to a panel surface of each of transmission type liquid crystal modules
28
,
29
and
30
in order that light exiting from the lens
14
a
may be focused on a panel surface of each of liquid crystal panels
42
to be described later.
The microlens array
15
is located substantially on a focal point of the lenses
14
a
. One each of the lenses
15
a
corresponds to one each of the lenses
14
a
and each lens
15
a
has such a shape that the most possible light exiting from the corresponding lens
14
a
can enter into the lens
15
a.
The microlens arrays
14
and
15
allow the emitted light from the light source
11
to uniformly enter into the panel surface of the liquid crystal panel, thereby serving to improve uniformity of an image to be displayed on a screen (the uniformity refers to the uniformity of brightness or color for displaying an image of the same brightness or color over the overall screen).
The polarizer
16
is a device for converting most of incoming unpolarized light into linearly polarized light (e.g., p-polarized light) and then allowing the linearly polarized light to exit. The polarizer
16
serves to improve the efficiency of utilization of the emitted light from the light source
11
and also serves to improve contrast of an image to be displayed on a screen by increasing the quantity of exiting light from the liquid crystal panel at the time of white display.
The p-polarized light exiting from the polarizer
16
is focused and impinges on a dichroic mirror
18
by a lens
17
. For example, the dichroic mirror
18
transmits red light of RGB light and reflects green light and blue light. Red p-polarized light passing through the dichroic mirror
18
is reflected by a mirror
19
, and the reflected light is focused on and enters into a liquid crystal module
28
by a lens
20
.
Green p-polarized light and blue p-polarized light reflected by the dichroic mirror
18
impinge on a dichroic mirror
21
. For example, the dichroic mirror
21
transmits blue light and reflects green light. The green p-polarized light reflected by the dichroic mirror
21
is focused on and enters into a liquid crystal module
29
by a lens
22
.
The blue p-polarized light passing through the dichroic mirror
21
is repeatedly focused and reflected by a lens
23
, a mirror
24
, a lens
25
, a mirror
26
and a lens
27
, and then the light enters into a liquid crystal module
30
.
The liquid crystal modules
28
,
29
and
30
have the same configuration.
FIG. 2
shows an example of a configuration of an optical system of each of the liquid crystal modules
28
,
29
and
30
. A sheet polarizer
41
is located close to the entry side of the transmission type liquid crystal panel
42
, and a polarizer
47
is located close to the exit side of the liquid crystal panel
42
. The polarizer
41
has the orientation of the axis of polarization (the axis of light transmission) which is determined so as to allow the p-polarized light to pass through the polarizer
41
. Therefore, the red p-polarized light, green p-polarized light and blue p-polarized light entering into the liquid crystal modules
28
,
29
and
30
, respectively, pass through the polarizers
41
as they are, and enter into the liquid crystal panels
42
.
The liquid crystal panel
42
is a TN (twisted nematic) liquid crystal panel, and changes the locus of a resultant electric field vector of light passing through liquid crystal molecules according to the level of a voltage applied to the liquid crystal molecules. A voltage is applied to the liquid crystal molecules of pixels of the liquid crystal panels
42
of the liquid crystal modules
28
,
29
and
30
in normally white mode according to the levels of video signals for red, green and blue. For example, an active matrix drive system is adopted as a system for driving the liquid crystal panel
42
.
Microlenses
44
, one each of which corresponds to one each of the pixels, are provided in a substrate
43
on the entry side of the liquid crystal panel
42
. The microlenses
44
are lenses for focusing light incident on the corresponding pixels on effective display area portions of the pixels (i.e., portions having no electrode, switching device and so on and thus capable of allowing light to pass through the portions). The microlenses
44
serve to substantially increase an ratio aperture of the liquid crystal panel
42
and also serve to improve the contrast of an image by increasing the quantity of exiting light from the liquid crystal panel
42
at the time of white display.
Light, which passes through a liquid crystal layer
45
of the liquid crystal panel
42
and then exits through a substrate
46
on the exit side, enters into the polarizer
47
. The orientation of the axis of polarization of the sheet polarizer
47
is perpendicular to that of the polarizer
41
, and therefore the polarizer
47
allows s-polarized light to pass through the polarizer
47
.
Red s-polarized light, green s-polarized light and blue s-polarized light passing through the polarizers
47
of the liquid crystal modules
28
,
29
and
30
enter into a dichroic prism
31
from three directions, as shown in FIG.
1
. The dichroic prism
31
has a filter film
31
a
for transmitting green light from the liquid crystal module
29
and reflecting red light from the liquid crystal module
28
in the same direction as the green light, and a filter film
31
b
for transmitting green light from the liquid crystal module
29
and reflecting blue light from the liquid crystal module
30
in the same direction as the green light. The red s-polarized light, green s-polarized light and blue s-polarized light are combined into one bundle of rays by the dichroic prism
31
.
The s-polarized light exiting from the dichroic prism
31
is projected onto a screen (not shown) via a projection optical system
32
.
As shown in
FIGS. 1 and 2
, the liquid crystal projector apparatus of the related art is devised to improve the uniformity by the microlens arrays
14
and
15
provided in a lighting optical system for guiding light emitted from the light source
11
to the liquid crystal modules
28
,
Miyasaka Sou
Shirochi Yoshiki
Suzuki Yoshio
Tanimoto Takeshi
Chung David Y.
Kim Robert H.
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