Projector and lamp unit

Details Projector and lamp unit Projector and lamp unit

1999-10-06

2002-10-22

Dowling, William (Department: 2851)

Optics: image projectors

Lamp control

Lamp position adjustable

C353S122000

Reexamination Certificate

active

06467911

ABSTRACT:

This application is based on applications Nos. H10-286152, H10-286153, H10-286154, H10-286179, H10-286181, and H10-286183 filed in Japan on Oct. 8, 1998, and Nos. H10-303659, H10-303715, H10-303726, H10-303730, and H10-303733 filed in Japan on Oct. 26, 1998, the entire content of which is hereby incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a projector, i.e. a projection-type image display apparatus, and to a light source unit for a projector.
2. Description of the Prior Art
A projector modulates light in accordance with an image, and projects the modulated light on a screen to display the image thereon. A projector is used to present an image to a number of people at a time, and is nowadays used even as a television monitor having a comparatively large screen.
FIG. 51
shows an example of the construction of a conventional projector, in the form of a horizontal cross section including the optical axis of the projection lens thereof. The projector
114
is composed of an illumination section, a display section, and a projection section. The illumination section illuminates the display section uniformly. The display section separates the illumination light into illumination light of three colors, i.e. red (R), green (G), and blue (B), then converts the illumination light of three colors individually into optical images of the corresponding colors, and then integrates the optical images of three colors together. The projection section projects the resulting integrated optical image.
The illumination section is provided with a light source
101
composed of a metal-halide lamp, a reflector
1
OZ formed as a reflecting mirror having the shape of a paraboloid of revolution so as to reflect the light emitted from the light source
101
and thereby form the light into a substantially parallel beam of light, a first lens array
103
and a second lens array
104
each having a plurality of lens cells arranged in a matrix, and a superimposing lens
105
.
The first lens array
103
is so arranged as to be optically conjugate with the three liquid crystal display panels
111
R,
111
G, and
111
B, which constitute the display section. The individual lens cells of the second lens array
104
are so arranged as to be optically conjugate with the light source
101
.
The white light emitted from the light source
101
is reflected by the reflector
102
so as to enter the first lens array
103
, which then separates the light into a plurality of light beams. These light beams enter the second lens array
104
, and then form a plurality of light source images. That is, the individual lens cells of the second lens array
104
serve as a secondary light source. The plurality of light beams exiting from the second lens array
104
are superimposed on one another by the superimposing lens
105
, and are led to the individual liquid crystal display panels
111
R,
111
G, and
111
B of the display section.
Next, the display section will be described. The display section is provided with, in addition to the liquid crystal display panels
111
R,
111
G, and
111
B that convert illumination light of three colors individually into optical images, field lenses
110
R,
110
G, and
110
B provided in front of the liquid crystal display panels
111
R,
111
G, and
111
B respectively, dichroic mirrors
106
a
and
106
b
that each transmit light of a specific wavelength range, turning mirrors
107
a
,
107
b
, and
107
c
, a condenser lens
108
, a relay lens
109
, and a cross dichroic prism
112
.
The dichroic mirror
106
a
transmits only R-color light. The dichroic mirror
106
b
transmits only B-color light. The R-color light transmitted through the dichroic mirror
106
a
is then reflected by the turning mirror
107
a
so as to pass through the field lens
110
R and then illuminate the liquid crystal display panel
111
R. The G-color light reflected from the dichroic mirrors
106
a
and
106
b
passes through the field lens
110
G and then illuminates the liquid crystal display panel
111
G. The B-color light reflected from the dichroic mirror
106
a
and transmitted through the dichroic mirror
106
b
travels via the condenser lens
108
, the turning mirror
107
b
, the relay lens
109
, the turning mirror
107
c
, and the field lens
110
B, and then illuminates the liquid crystal display panel
111
B.
The distance from the light source to the liquid crystal display panel
111
B is different from the distance from the light source to the liquid crystal display panel
111
R or
111
G. This is the reason that the condenser lens
108
and the relay lens
109
are used, which serve to make the illumination condition of the liquid crystal display panel
111
B identical with that of the liquid crystal display panel
111
R or
111
G. The field lenses
110
R,
110
G, and
110
B serve to achieve telecentric illumination of the liquid crystal display panels
111
R,
111
G, and
111
B.
The cross dichroic prism
112
has a cementing surface
112
a
to which a dichroic coating that reflects only B-color light is applied and a cementing surface
112
b
to which a dichroic coating that reflects only R-color light is applied. On the liquid crystal display panels
111
R,
111
G, and
111
B are formed optical images of the R, G, and B colors respectively. The light beams conveying these optical images enter the cross dichroic prism
112
, where they are integrated together as a result of the R-color light being reflected by the cementing surface
112
b
and the B-color light being reflected by the cementing surface
112
a
. The resulting integrated light beam is then led to the projection lens
113
, which constitutes the projection section. The projection lens
113
projects the light beam led thereto on a screen (not shown).
As described previously, the plurality of light beams exiting from the second lens array
104
of the illumination section are superimposed on one another when illuminating the liquid crystal display panels
111
R,
111
G, and
111
B. This makes it possible to illuminate the liquid crystal display panels
111
R,
111
G, and
111
B with an uniformly distributed amount of light, and thereby form a color image with uniformly distributed brightness on the screen.
A projector is expected to project a bright image efficiently. To achieve this, various projectors have conventionally been proposed that are provided with some means that serves the purpose. For example, in the conventional projector shown in FIG.
51
and described above, uniform illumination is achieved by an ingenious design of the illumination section to make it possible to use the light from the light source efficiently and thereby project a bright image.
Moreover, in recent years, developments have been made also in technologies related to lamps for use as a light source. By the use of a bright lamp, it is possible to obtain bright illumination easily. As an example of recently developed lamps, an ultra-high-pressure lamp (UHP lamp) is known. A UHP lamp offers higher efficiency than a metal-halide lamp as is used as the light source in the conventional projector described above.
FIG. 52
shows a graph representing the relationship between brightness and electric power consumption for these two types of lamp.
In
FIG. 52
, the horizontal axis represents brightness, and the vertical axis represents electric power consumption; the dash-and-dot line
150
indicates the relationship observed in a metal-halide lamp, and the solid line
151
indicates the relationship observed in a UHP lamp. For example, to obtain brightness I
1
, whereas a metal-halide lamp requires electric power consumption W
1
, a UHP lamp requires W
2
, which is lower than W
1
. In other words, with the same electric power consumption W
1
, a UHP lamp offers brightness
12
higher than the brightness I
1
that a metal-halide lamp offers.
That is, in comparison with a metal-halide lamp, a UHP lamp offers given brightness with less electric power consumption, and thus permits brighter display without ex

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