Optics: image projectors – Plural
Reexamination Certificate
2001-05-25
2003-04-08
Dowling, William (Department: 2851)
Optics: image projectors
Plural
C353S098000
Reexamination Certificate
active
06543900
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a light valve projection apparatus for magnified projection of an image of a liquid crystal panel or a micromirror rocking pixel panel, and more particularly to a projection apparatus equipped, as the light source, with a light source of instantly light emitting type and that of high efficiency and high color presenting ability. The present invention is applicable to a projector of front projection type for direct projection onto a reflective screen, a projection of rear projection type for projection on a transmissive screen, or an apparatus in which either of the foregoing is combined with another equipment, utilizing a transmissive or reflective liquid crystal device or a micro mirror rocking pixel device.
2. Related Background Art
There are already commercialized apparatus for magnified projection of the image of a light valve panel such as a liquid crystal device, utilizing a light source such as a metal halide lamp.
In such apparatus the light emitted from the light source is concentrated on a light valve panel for example through a mirror, and is projected through a projection lens onto a screen.
The apparatus is known in various types such as a single panel type utilizing a liquid crystal panel, and a three-panel type in which three liquid crystal panels are illuminated by color separation through dichroic mirrors and the transmitted lights are color synthesized, and the liquid crystal panel of transmissive type is adopted for this purpose but that of reflective type is also utilized recently.
Also instead of the liquid crystal panel, there has been developed a panel in which micromirrors are arrayed on a semiconductor chip as pixels and the micromirror of each pixel is driven in a rocking motion to control the gradation, and such panel is also utilized in a single panel type utilizing color-sequential light sources and a three-panel type in which three panels are illuminated by color separation through dichroic mirrors and the reflected lights are color synthesized.
The illumination for such projector is required to be of a high illumination intensity in order that the projected image can be viewed on a large screen even in a well lighted room, and, for this reason, the light source is principally composed of a metal halide lamp or a high pressure mercury lamp of high efficiency and high color presenting ability.
FIG. 11
shows an example of the configuration of a conventional liquid crystal projector of three panel type.
In
FIG. 11
, there are shown a metal halide lamp la which is a discharge tube, a reflector
1
b
formed in an elliptic or parabolic surface, an electrode
1
c
of the metal halide lamp
1
a
, a first fly's eye lens
7
, dichroic mirrors
8
,
9
, mirrors
10
,
11
,
12
, a cross dichroic prism
13
, a projection lens
14
, a red-color transmissive liquid crystal panel
15
, a green-color transmissive liquid crystal panel
16
, a blue-color transmissive liquid crystal panel
17
, an optical system shielding case
18
, and an external casing
100
containing the entire projection system.
When a power switch of the apparatus shown in
FIG. 11
is turned on, the metal halide lamp
1
a
is energized and starts lighting.
Then the light emitted from the metal halide lamp
1
a
is converted into a relatively parallel illuminating light by the reflector
1
b
and enters the fly's eye lens
5
.
The fly's eye lens
5
has a composite structure of plural lenses and has an effect, in combination with a fly's eye lens
7
, of flattening the luminance on an irradiated surface at the rear.
A mirror
6
bends the optical path of the illuminating light from the fly's eye lens
5
by 90° for entry into the fly's eye lens
7
.
The mirror
6
is provided with a dichroic film for transmitting infrared and ultraviolet light, thereby reducing the infrared and ultraviolet components in the visible light entering the fly' eye lens
7
and thus reducing heat generation and improving reliability.
The visible light emerging from the fly's eye lens
7
enters a dichroic mirror
8
through which blue light is transmitted, then bent in the optical path by a mirror
10
and enters a transmissive liquid crystal panel
17
for blue color.
On the other hand, in the dichroic mirror
8
, the light of green and red colors, having a wavelength longer than that of blue color, is reflected and enters a dichroic mirror
9
.
The dichroic mirror
9
has a property of reflecting green light and illuminates a transmissive liquid crystal panel
16
for green color.
In the dichroic mirror
9
, the light red color, having a wavelength longer than that of the green color, is reflected, then bent in the optical path by mirrors
11
,
12
and illuminates a transmissive liquid crystal panel
15
for red color.
The aforementioned liquid crystal panels
15
,
16
,
17
respectively for red, green and blue colors receive unrepresented drive signals for the respective colors to display an image in the display area of each panel, thereby optically modulating the illuminating light mentioned above.
The image displayed on the green liquid crystal panel
16
is being vertically inverted (
FIG. 11
being a plan view) electrically or by reversing the front and back surfaces of the panel with respect to the images displayed on the liquid crystal panels
15
,
17
for other colors, in consideration of the process of image synthesis in a dichroic mirror
13
.
The image lights from the transmissive liquid crystal panels
15
,
16
,
17
for the red, green and blue colors enter a cross dichroic prism
13
respectively from predetermined directions as illustrated, thus being synthesized and emerging as a color image from an illustrated fourth face and enters a projection lens
14
for magnified projection onto a screen.
Also a configuration employing two light sources is disclosed in the Japanese Utility Model Application Laid-open No. 4-33034 and the Japanese Patent Application Laid-open No. 9-127467.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a preferred configuration employing plural light sources in a projection apparatus.
If the light source of a projection apparatus of liquid crystal panel type or micromirror rocking pixel panel type is composed of a discharge lamp of high efficiency and high color presenting ability such as a metal halide lamp or a high pressure mercury lamp, there is required a time of at least 2 to 3 minutes until such illuminating lamp reaches a predetermined light amount after the power supply is turned on.
Also in case of recovery from an instantaneous interruption of the power supply for certain reason, there is required an even longer time (3 to 5 minutes) before the lamp can be turned on again. Thus, there is encountered a serious drawback that the image cannot be projected during such period, particularly in applications requiring urgency, such as important presentations or conferences.
In such situation, the presence of plural light sources may be advantageous for illuminating the light valve. The present invention is to provide, in case of employing plural light sources, a configuration capable of efficiently illuminating the light valve or a configuration enabling simplification even in case of using plural light sources.
According to one of the inventions of the present application, there is provided a projection apparatus provided with a light valve which modulates light by two-dimensionally arranged plural pixels and projects thus modulated light, the apparatus comprising:
a first light source;
a second light source;
a mirror for guiding the light from the first light source or the light from the second light source; and
a movable mechanism for varying the relative position between the mirror and the first and second light sources.
In such configuration, owing to the presence of the movable mechanism for changing the relative position between the mirror and the light sources, there can be switched a state in which the firs
Hirobe Toshinori
Kadota Shigehiro
Noji Minoru
Shigeta Kazuyuki
Yasumura Hiroto
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