Optics: image projectors – Composite projected image – Multicolor picture
Reexamination Certificate
1998-12-18
2001-02-13
Metjahic, Safet (Department: 2858)
Optics: image projectors
Composite projected image
Multicolor picture
C353S034000, C353S037000
Reexamination Certificate
active
06186629
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical device that can efficiently apply light to a light modulation device (display device) such as a liquid crystal display panel and can be miniaturized, as well as to a display apparatus having such an optical device.
2. Description of the Related Art
Recently, display apparatuses such as a projector apparatus, a television receiver, and a computer display that use an optical device such as a liquid crystal display panel that is a light modulation device called a light bulb have spread in a variety of fields.
In such display apparatuses using a liquid crystal display panel or the like, a light beam that is emitted from a light source having ametal halide lamp, a halogen lamp, or the like is separated into beams of the three primary colors, which are input to a liquid crystal display panel having color filters (R, G, and B) that are provided for the respective colors to improve the color purity. The three beams are modulated by the liquid crystal display panel in accordance with an input video signal and then combined with each other to generate color video signal light, which is projected onto a screen via a projection lens in an enlarged manner.
In the above type of optical system, it is required that a light beam that is emitted from the light source be applied to the liquid crystal display panel efficiently and uniformly. However, the light-emitting surface of the light source has some surface area and hence it is difficult to use the light source as an ideal point light source; a light beam emitted from a real light source has a large divergence angle. Therefore, it is difficult to apply efficiently a light beam emitted from the light source to the liquid crystal display panel.
One generally known method of efficiently applying a light beam that is emitted from a light source and has a large divergence angle to a liquid crystal display panel is such that a light beam to be input to the liquid crystal display panel is converged and uniformized in illuminance profile by using, for example, a lens array in which a number of small lenses are arranged in matrix form.
A general example using such a lens array will be described below with reference to FIG.
1
. In a light source
510
, a metal halide lamp
510
a
, for example, is disposed at the focal position of a paraboloid mirror, whereby a light beam that is approximately parallel with the optical axis of the paraboloid mirror is output from its opening. Unnecessary components in the infrared (IR) range and the ultraviolet (UV) range of the light beam output from the light source
510
are interrupted by a UV/IR-cutting filter
511
and only the effective light beam is introduced to a downstream first optical block
501
.
The first optical block
501
is constituted of optical elements including a first lens array
512
in which a plurality of convex cell lenses
512
a
each having an outer shape that is approximately similar (equal in aspect ratio) to the effective apertures of liquid crystal display panels
517
,
521
, and
527
as light modulation devices (light spatial modulation devices) are arranged in matrix form.
A second lens array
513
of a second optical block
502
that is disposed downstream of the first optical block
501
is formed with a plurality of convex cell lenses
513
a
on the incidence side and with a single convex surface
513
b
as a first converging component on the exit side.
Dichroic mirrors
514
and
519
for separating a light beam that has been emitted from the light source
510
into beams of red, green, and blue are disposed between the second lens array
513
and the effective apertures of the liquid crystal display panels
517
,
521
, and
527
.
In the example of
FIG. 1
, a red beam R is reflected and a green beam G and a blue beam B are transmitted by the dichroic mirror
514
. The red beam R reflected by the dichroic mirror
514
is bent in traveling direction by 90° by a mirror
515
, converged by a condenser lens
516
, and finally input to the red liquid crystal display panel
517
.
On the other hand, the green beam G and the blue beam B that have passed through the dichroic mirror
514
are separated from each other by a dichroic mirror
519
. That is, the green beam G is reflected and bent in traveling direction by 90° by the dichroic mirror
519
and then introduced to the green liquid crystal display panel
521
via a condenser lens
520
. The blue beamB passes through the dichroic mirror
519
(goes straight) and is then introduced to the blue liquid crystal display panel
527
via relay lenses
522
and
524
, a condenser lens
526
, and mirrors
523
and
525
.
A polarizing plate (not shown) for polarizing incident light in a predetermined direction is disposed on the incidence side of each of the liquid crystal display panels
517
,
521
, and
527
and a polarizing plate (not shown) that transmits only a component having a prescribed polarization plane of exit light is disposed downstream of each of the liquid crystal display panels
517
,
521
, and
527
so that the light intensity is modulated in accordance with the voltage of a liquid crystal driving circuit.
The beams of the respective colors that have been modulated by the liquid crystal display panels
517
,
521
, and
527
are combined with each other by a dichroic prism
518
as a light composing means. In the dichroic prism
518
, the red beam R and the blue beam B are reflected by respective reflection surfaces
518
a
and
518
b
so as to be directed to a projection lens
530
. The green beam G passes through the reflection surfaces
518
a
and
518
b
. As a result, the R, G, and B beams are combined together so as to travel along the same optical axis, and are then projected onto a screen (not shown) by the projection lens
530
in an enlarged manner.
Next, the optical system including the respective lens arrays
512
and
513
of the first optical block
501
and the second optical block
502
will be described in more detail with reference to
FIGS. 2
,
3
, and
4
A-
4
B.
FIG. 2
shows an example of how beams are formed mainly by the optical characteristic of the first optical block
501
. A god light beam L emitted from the light source is divided by the cell lenses
512
a
of the first lens array
512
and, after exiting from the first optical block
501
, forms images corresponding to the respective cell lenses
512
a
of the first lens array
512
in the vicinity of the second optical block
502
.
Then, the beams are introduced to the condenser lens
520
as a second converging component by the first converging component
513
b.
At this time, image points of cells in a peripheral portion of the first lens array
512
become large-angle-of-view object points of the condenser lens
520
as the second converging component. In this manner, images formed in the vicinity of the second optical block
502
by the respective cell lenses
512
a
of the first lens array
512
are re-imaged in the vicinity of an entrance pupil E of the projection lens
530
by the condenser lens
520
as the second converging component.
FIG. 3
shows an example of how a light beams are formed mainly by the second optical block
502
. A divergence angle &thgr; of a beam that can be captured from the above-described illumination system can be controlled by properly setting the external dimensions of each cell lens
513
a
of the second lens array
513
and the interval between the first lens array
512
and the second lens array
513
.
Beams thus captured within the divergence angle &thgr; are introduced to the condenser lens
520
as the second converging component by the convex surface
513
b
as the first converging component, and applied, efficiently and uniformly, to the liquid crystal display panel
521
by a composite converging component that is a combination of the first and second converging components.
However, the above action causes the following problems. A beam that passes through a central portion of the convex surface
Iwamura Atsushi
Kanamori Tatsuru
Kawai Toru
Frommer William S.
Frommer Lawrence & Haug LLP.
LeRoux Etienne
Metjahic Safet
Sony Corporation
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