Optics: image projectors – Color filter
Reexamination Certificate
2003-08-04
2004-09-28
Dowling, William C. (Department: 2851)
Optics: image projectors
Color filter
C348S743000
Reexamination Certificate
active
06796661
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a projection type display device that displays an image on the basis of projection of a light modulated by a light valve.
2. Related Background Art
Projection type display devices of various structures have hitherto been proposed which display an image on the basis of projection of a light modulated by a light valve such as a liquid crystal panel.
One of such projection type display devices rotatively drives a color wheel to spectrally separate a white light and utilizes the separated light to achieve color display.
FIG. 3
is a schematic view showing an example of a structure of a conventional projection type display device. In this figure, reference numerals
1
,
1
a
and
1
b
denote a projection lamp, a lamp bulb, and an ellipsoidal reflector, respectively. Reference numerals
2
,
3
,
3
a
and
3
b
denote a color wheel, a rod integrator lens, an entrance end face, and an exit end face, respectively. Reference numerals
4
,
5
,
10
,
11
and
12
denote a relay lens, a field lens, a light valve, a projection lens, and a housing, respectively. Reference characters m, M and A
1
denote an axis of rotation, a motor, and an optical axis, respectively. Reference characters L
11
, L
12
and D
3
denote an exiting light, an exiting light and a projection type display device, respectively.
The projection type display device D
3
comprises the projection lamp
1
that emits a white light. The projection type display device D
3
has the following components sequentially arranged on its light emission side:
the color wheel
2
that sequentially separates the white light into respective colors on the basis of rotative driving effected by the motor M;
the rod integrator lens (hereinafter referred to as “rod lens”)
3
used to optimally irradiate a display area of the light valve
10
with the light;
the relay lens
4
;
the field lens
5
;
the light valve
10
that modulates the irradiation light; and
the projection lens
11
that enlarges and projects the light modulated by the light valve
10
, on a screen (not shown).
FIG. 4
is a sectional view showing the structure of the projection lamp
1
in detail. As shown in this figure, the projection lamp
1
is composed of the lamp bulb
1
a
and the ellipsoidal reflector
1
b
placed behind the lamp bulb
1
a
. The ellipsoidal reflector
1
b
has a reflecting surface shaped like an ellipsoidal surface (see reference character R
1
) that is rotationally symmetric with respect to the optical axis A
1
. The ellipsoidal reflector
1
b
has two focuses (hereinafter referred to as “first focus F
1
” and “second focus F
2
”). The lamp bulb
1
a
(to be exact, its portion that emits light) is placed at the first focus F
1
.
Further, as shown in
FIG. 5
, the color wheel
2
is divided into a plurality of color filter sections
2
R,
2
G and
2
B (for example, three color filter sections for red, blue, and green or four color filter sections for red, blue, green, and transparency). The color wheel
2
is rotatively driven by the motor M to sequentially separate the white light spectrally.
Furthermore, the rod lens
3
is an optical element shaped like a square pole and is formed of transparent glass or a resin material. The side surfaces (i.e., surfaces other than the entrance end face
3
a
and exit end face
3
b
) of the rod lens are each a total reflection surface. Further, reference numeral
12
denotes the housing.
When the projection lamp
1
is energized, the emitted light L
11
is condensed by the ellipsoidal reflector
1
b
and then spectrally separated by the color wheel
2
. The region of the light L
11
that has got out of the projection lamp
1
is represented by a triangle including two sides shown by dotted lines in FIG.
4
. That is, the region is a triangle region including two dotted lines that cross at the second focus F
2
of the four dotted lines shown in FIG.
4
. Subsequently, the light enters the rod lens
3
through the entrance end face
3
a
and is then totally reflected by the side surface of the rod lens
3
(or exits through the exit end face
3
b
without being totally reflected) to form a uniform light. The exiting light L
12
passes through the relay lens
4
and the field lens
5
to produce a flux of parallel light, which then passes through the light valve
10
to be thereby converted into an optical image, which then passes through the projection lens
11
to be finally projected on the screen (not shown).
FIG. 6
shows a projection type display device D
4
of another configuration. As shown by reference numeral
6
in
FIG. 6
, a total reflection mirror is placed above the projection lamp
1
. This device is adapted to reflect a light from the projection lamp
1
, from a direction along an optical axis A
1
to a direction along an optical axis A
2
.
However, with the projection type display device D
4
of the structure shown in
FIG. 6
, the color wheel
2
or the motor M may interfere with the ellipsoidal reflector
1
b
or may block the light L
11
irradiated to the ellipsoidal reflector
1
b
by the lamp bulb
1
a
. This is because, as shown in the figure, the color wheel
2
is partly located in the triangular region of the light L
11
getting out of the projection lamp
1
.
To obviate this problem, a projection type display device D
5
of another configuration has been proposed. This is shown in FIG.
7
. As shown in the figure, when the color wheel
2
and the motor M are placed above the optical axis A
2
, a sufficient space must be provided above the optical axis A
2
, which poses another problem that the size of the device will increase.
SUMMARY OF THE INVENTION
It is, therefore, an object of the present invention to provide a projection type display device that is free from the above problems.
The present invention has been accomplished in view of the above circumstances and provides a projection type display device comprising a light source for emitting a white light, a reflecting means for reflecting the emitted light, a color wheel comprising a plurality of color filter sections of different colors for sequentially separating the light from the light source into different colors on the basis of rotative driving, and a light valve for modulating the separated light, the light from the light source being separated by the color wheel, modulated by the light valve and then projected, wherein the color wheel is disposed in an area interposed between a light entering (or incident on) the reflecting means and a light exiting the reflecting means such that the light from the light source passes through the color wheel in such a converged shape as to pass through only a single color filter section.
REFERENCES:
patent: 5463433 (1995-10-01), Koo
patent: 5467146 (1995-11-01), Huang et al.
patent: 5612753 (1997-03-01), Poradish et al.
patent: 5863125 (1999-01-01), Doany
patent: 6467910 (2002-10-01), Sato
patent: 6575579 (2003-06-01), Ho
Canon Kabushiki Kaisha
Dowling William C.
Morgan & Finnegan L.L.P.
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