Liquid crystal cells – elements and systems – Liquid crystal system – Projector including liquid crystal cell
Reexamination Certificate
1998-09-24
2001-04-17
Dudek, James A (Department: 2871)
Liquid crystal cells, elements and systems
Liquid crystal system
Projector including liquid crystal cell
C349S007000, C349S008000, C349S066000, C349S095000
Reexamination Certificate
active
06219111
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a projection-type liquid crystal display apparatus for displaying an image onto a screen by enlarging and projecting an image on a liquid crystal panel by means of an optical projection system and particularly to a projection-type liquid crystal display apparatus comprising a single liquid crystal panel without any color filter.
2. Description of the Related Art
Projection-type liquid crystal apparatuses such as liquid crystal projectors and liquid crystal projection television sets have been developed for enlarging and projecting an image on a liquid crystal panel as an optical switching device by means of an optical projection system. Such liquid crystal display apparatuses include a single-panel apparatus comprising a liquid crystal panel having three color filters (CF) of blue (B), red (R) and green (G) and a triple-panel apparatus comprising monochrome liquid crystal panels each provided in optical paths of B, R and G, respectively. The single-panel apparatus has a simple configuration and reductions in size, weight and cost are easily achieved. However, it is difficult to achieve high luminance since the color filters absorb much light. Cooling of the apparatus is thereby affected as well.
In order to overcome these problems, single-panel color liquid crystal display apparatuses are disclosed in, for example, Japanese Patent Application Laid-open No. 4-60538 (1992) that corresponds to U.S. Pat. No. 5,161,042 and ‘Asia Display '95 (p. 887)’ wherein one condenser microlens is opposed to every three pixels. Three color rays of B, R and G are entered to each microlens from mutually different directions and condensed. The light sent out from the microlens is entered to each of the three pixels corresponding to three colors of B, R and G, respectively. In the color liquid crystal display apparatus, it is possible to effectively utilize light incident on regions between pixels (black matrix regions where thin film transistors [TFf], that is, switching devices for driving pixels are formed) as well. The substantial aperture ratio (the ratio of effective pixel area to the whole pixel area) is thereby increased and high illuminance is achieved, accordingly. Since such a projection-type liquid crystal display apparatus comprises a single liquid crystal panel with a microlens array instead of a color filter, the apparatus of this type will be called projection-type liquid crystal display apparatus of the color-filterless single-panel microlens system.
FIG. 1
is a schematic view of a proposed optical system used in the projection-type liquid crystal display apparatus of the color-filterless single-panel microlens system. The apparatus comprises: a light source
501
for emitting white light; a UV-IR cut filter
502
for removing ultraviolet and infrared rays from the white light emitted from the light source
501
; a glass rod integrator
503
for unifying the intensity distribution in a cross section of a bundle of rays passing through the UV-IR cut filter
502
; a relay lens
504
for condensing the ray bundle sent out from the glass rod integrator
503
; and a collimator lens
505
for transforming the ray bundle sent out from the relay lens
504
into a nearly parallel ray bundle. The display apparatus further comprises: dichroic mirrors
506
B,
506
R and
506
G placed in the optical path behind the collimator lens
505
for splitting the white ray bundle sent out from collimator lens
505
into color rays of B, R and G and reflecting the color rays at angles different from one another; an incident polarizing plate
507
for transforming the color rays split by the dichroic mirrors
506
B,
506
R and
506
G into light linearly polarized in a specific direction; a liquid crystal panel
508
for performing intensity modulation on the color rays passing through the polarizing plate
507
based on color image signals; and a projection lens
509
for condensing the light sent out from the liquid crystal panel
508
and projecting the light onto a screen
509
and composing the light.
The light source
501
is typically made up of an emitter
501
a
of metal-halide and a concave mirror
501
b
of rotation symmetry. The glass rod integrator
503
is made of glass in the shape of prism and unifies the intensity distribution in a cross section of the ray bundle incident from one end face of the integrator by reflecting the ray bundle inside a number of times and emits the ray bundle from the other end face. The liquid crystal panel
508
is a panel of the color-filterless microlens system, including pixel electrodes (not shown) regularly arranged in two dimensions in correspondence with the colors of R, G and B, condenser microlenses (not shown) each of which is opposed to every three pixel electrodes of R, G and B with a liquid crystal layer not shown in between, and an outgoing polarizing plate not shown. The condenser microlens mentioned above condenses rays of three colors B, R and G split by the dichroic mirrors
506
B,
506
R and
506
G and entering at mutually different angles. The condenser microlens then has the rays each enter the respective pixels corresponding to the three colors of B, R and G.
In the projection-type liquid crystal display apparatus with such a configuration, spatial modulation is selectively performed on each of the rays of three colors B, R and G incident into the liquid crystal layer provided for each pixel, based on a color image signal for each color applied to each pixel electrode of the liquid crystal panel
508
. The rays of color light modulated at the liquid crystal panel
508
form an image on the screen
510
by the projection lens
509
and the colors are thus synthesized. A color image is thereby projected onto the screen
510
.
As described above, the projection-type liquid crystal display apparatus utilizes the glass rod integrator
503
as a means for smoothing the luminous distribution on the liquid crystal panel
508
. In this case, the outgoing face of the glass rod integrator
503
is conjugated with the surface of the liquid crystal panel
508
. As a result, a foreign substance such as dust deposited on the outgoing face of the integrator
503
may be enlarged and projected onto the screen
510
. The quality of the image is thereby significantly reduced.
In the display apparatus, although the intensity distribution in a cross section of the outgoing ray bundle is smoothed to some degree by internal reflection of the glass rod integrator
503
, some light directly reaches the outgoing face without internal reflection if the length of the integrator
503
is reduced in order to decrease the size of the apparatus as a whole. Therefore, there is limitation on smoothing the illuminance distribution on the liquid crystal panel
508
. Consequently, if arc fluctuations occur in the emitter of the light source
501
, the fluctuations result in flicker of the image. The image quality is thereby reduced.
In Japanese Patent Application Laid-open No. 5-346557 (1993), for example, a projection-type triple-panel liquid crystal display apparatus utilizing a multiple lens array integrator is disclosed. Instead of the rod integrator, the apparatus comprises the multiple lens array integrator made up of a first lens array wherein a plurality of lenses are arranged in two dimensions and a second lens array wherein a plurality of lenses paring up with the respective lenses of the first lens array are arranged in two dimensions.
However, the multiple lens array integrator disclosed in the publication mentioned above is particularly developed for a related-art projection-type liquid crystal display apparatus using a liquid crystal panel with color filters and a triple-panel display apparatus. The configuration of the multiple lens array integrator is therefore not applicable to the apparatus of the colorfilterless single-panel microlens system. No suggestion is made in the above-mentioned publication for such applications of the integrator, either. There are
Fukuda Toshihiro
Nakamura Akira
Dudek James A
Kananen Ronald P.
Rader Fishman & Grauer
Sony Corporation
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