Television – Video display – Projection device
Reexamination Certificate
2001-09-17
2004-10-12
Kostak, Victor R. (Department: 2614)
Television
Video display
Projection device
C348S745000
Reexamination Certificate
active
06803971
ABSTRACT:
BACKGROUND OF THE INVENTION
FIELD OF THE INVENTION
The present invention relates to a projection type video display device having a plurality of light sources.
FIG. 7
is a plan view showing an optical system in a four-light and triple-plate liquid crystal projector. An illuminating device
1
comprises two light sources
1
a
and
1
b
arranged opposite to each other and two light sources
1
c
and
1
d
similarly arranged opposite to each other, an optical path changing member
2
arranged between the light sources
1
a
and
1
b
, and an optical path changing member
3
arranged between the light sources
1
c
and
1
d
. The light sources
1
a
and
1
b
are shifted upward, as shown in FIG.
8
(
a
), with respect to the light sources
1
c
and
1
d
. Each of the light sources is composed of an extra-high pressure mercury lamp, a metal halide lamp, a xenon lamp, or the like, and light irradiated by the light source is emitted after being changed into parallel light by a parabola reflector, and is introduced into an integrator lens
4
. The integrator lens
4
comprises a pair of groups of lenses, and each lens portion introduces the light emitted from each of the light sources
1
a
,
1
b
,
1
c
, and
1
d
into the whole surface of a liquid crystal light valve, described later. A state where the light from each of the light sources is incident on the integrator lens
4
is as illustrated in FIG.
8
(
b
). The light which has passed through the integrator lens
4
is introduced into a first dichroic mirror
7
after passing through a polarized light converter
5
and a condenser lens
6
.
The first dichroic mirror
7
transmits light in a red wavelength band, while reflecting light in a cyan (green+blue) wavelength band. The light in the red wavelength band which has passed through the first dichroic mirror
7
is reflected on a reflecting mirror
9
through a concave lens
8
so that its optical path is changed. The red light which has been reflected on the reflecting mirror
9
is optically modulated by passing through a light transmission-type liquid crystal light valve for red
31
through a lens
10
. On the other hand, the light in the cyan wavelength band which has been reflected on the first dichroic mirror
7
is introduced into a second dichroic mirror
12
through a concave lens
11
.
The second dichroic mirror
12
transmits light in a blue wavelength band, while reflecting light in a green wavelength band. The light in the green wavelength band which has been reflected on the second dichroic mirror
12
is introduced into a light transmission-type liquid crystal light valve for green
32
through a lens
13
and is optically modulated by passing through the liquid crystal light valve
32
. The light in the blue wavelength band which has passed through the second dichroic mirror
12
is introduced into a light transmission-type liquid crystal light valve for blue
33
through a relay lens
14
, a total reflecting mirror
15
, a relay lens
16
, a total reflecting mirror
17
, and a relay lens
18
, and is modulated by passing through the liquid crystal light valve
33
.
Modulated light beams (video light beams in respective colors) which have been modulated by passing through the liquid crystal light bulbs
31
,
32
,
33
are synthesized by a dichroic prism
19
, to obtain color video light. The color video light is projected in enlarged fashion by a projection lens
20
, and is projected and displayed on a screen
21
.
Meanwhile, the first dichroic mirror
7
has the property of transmitting a wavelength larger than a certain wavelength and reflecting a wavelength shorter than the certain wavelength. However, a wavelength having a transmission rate of 50% (a half wavelength) varies depending on an angle of incidence, as shown in FIGS.
9
(
a
) and
9
(
b
). That is, one of an angle at which light from the light sources
1
a
and
1
c
is incident on the first dichroic mirror
7
and an angle at which light from the light sources
1
b
and
1
d
is incident on the first dichroic mirror
7
is represented by a symbol C in
FIG. 9
, and the other thereof is represented by a symbol B. Consequently, a difference occurs between a color component in a case where the light from the light sources
1
a
and
1
c
passes through the first dichroic mirror
7
and a color component in a case where the light from the light sources
1
b
and
1
d
passes through the first dichroic mirror
7
.
Furthermore, as shown in FIGS.
10
(
a
) and
10
(
b
), the light transmission rate of each of the liquid crystal light bulbs
31
,
32
, and
33
varies depending on the angle of incidence of light. Light from a certain light source enters a certain liquid crystal light bulb leftward from the right, while entering a certain liquid crystal light valve rightward from the left. Further, light from a certain light source enters a certain liquid crystal light valve downward from the top, while entering the liquid crystal light valve
33
upward from the bottom by passing through the relay lenses
14
and
16
and the relay lens
18
. The direction in which light enters a liquid crystal light valve may be reversed. That is, light entering a certain liquid crystal light valve from a certain light source is represented by a symbol C in FIG.
10
, while light entering a certain liquid crystal light valve from a certain light source is represented by a symbol B.
FIGS. 11 and 12
illustrate a state where a chromaticity coordinate y in a case where only one of the light sources is put on is changed in the horizontal direction at the center of projected video, where FIG.
11
(
a
) is a characteristic view at the time when the light source
1
a
is put on, FIG.
11
(
b
) is a characteristic view at the time when the light source
1
b
is put on, FIG.
12
(
a
) is a characteristic view at the time when the light source
1
c
is put on, and FIG.
12
(
b
) is a characteristic view at the time when the light source
1
d
is put on. As apparent from the drawings, color nonuniformity and a change in white color temperature occur in putting on only one of the light sources. This is caused by a phenomenon described in
FIGS. 9 and 10
. On the other hand, in a state where all the four light sources
1
a
,
1
b
,
1
c
, and
1
d
are put on, the color nonuniformity is canceled by canceling the characteristics of the light sources. Accordingly, the value of Y is made constant, as shown in
FIG. 13
, so that the color nonuniformity is canceled, and an objective color temperature is obtained in the white color temperature.
In a state where all the four light sources
1
a
,
1
b
,
1
c
, and
1
d
are put on, as shown in FIG.
14
(
a
) however, the color nonuniformity is canceled by canceling the characteristics, as described above. On the other hand, in a case where one of the light sources (the light source
1
a
in the drawing) stops emitting light by blowing its bulb, for example, as shown in FIG.
14
(
b
) the canceling state is changed, causing color nonuniformity. From the same reason, a white color temperature is changed. It goes without saying that even in a case where two or more of the light sources stop emitting light, the canceled state may be changed, causing color nonuniformity and a change in white color temperature.
The present invention has been made in view of the above-mentioned circumstances, and has for its object to provide a projection type video display device capable of restraining, in a case where it has a plurality of light sources, the occurrence of color nonuniformity and the change in white color temperature even when one or more of the light sources stop emitting light.
SUMMARY OF THE INVENTION
In order to solve the above-mentioned problem, a projection type video display device according to the present invention is characterized by comprising an illumination optical system having a plurality of light sources for introducing light emitted from each of the light sources toward a partial area of an integrator lens to irradiate the whole area of the integrator lens; a color sepa
Koba Hiroki
Sasaki Yoshihiro
Yamamoto Hideki
Kostak Victor R.
Sanyo Electric Co,. Ltd.
Westerman Hattori Daniels & Adrian LLP
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