Illumination – Light source and modifier – Plural serial lens elements or components
Reexamination Certificate
2001-05-29
2003-04-15
Cariaso, Alan (Department: 2875)
Illumination
Light source and modifier
Plural serial lens elements or components
C362S244000, C362S331000, C362S019000, C359S619000
Reexamination Certificate
active
06547421
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a video display apparatus for projecting a still picture or a moving picture with a high color reproduction capability.
A video display apparatus of the projection type which uses light emitted from a light source to project and display a still picture or a moving picture upon a screen is conventionally used practically.
Typically, a video display apparatus of the projection type which is conventionally used widely has such a configuration as shown in FIG.
1
. Referring to
FIG. 1
, the video display apparatus of the projection type includes a reflecting plate
100
having a reflecting surface of a shape of a paraboloid of revolution, a light source
101
disposed at a focus position of the reflecting plate
100
, an integrator
102
, a red separating mirror
103
R, a green separating mirror
103
G, a reflecting mirror
103
B, and a color synthesizing prism
104
having a cubic shape.
The video display apparatus further includes a reflecting mirror
105
R for reflecting red light reflected by the red separating mirror
103
R so as to be introduced into a predetermined surface
104
R of the color synthesizing prism
104
, and a reflecting mirror
105
B for reflecting blue light reflected by the reflecting mirror
103
B so as to be introduced into another surface
104
B of the color synthesizing prism
104
parallel to the surface
104
R. The color synthesizing prism
104
is disposed such that green light reflected by the green separating mirror
103
G is introduced into a surface
104
G thereof perpendicular to the surface
104
R and the surface
104
B. A pair of optical path length adjusting lenses
106
and
107
are disposed between the green separating mirror
103
G and the reflecting mirror
103
B and between the reflecting mirror
103
B and the reflecting mirror
105
B, respectively.
The video display apparatus further includes a red light valve
108
R interposed between the reflecting mirror
105
R and the surface
104
R of the color synthesizing prism
104
, a red lens
109
R interposed between the reflecting mirror
105
R and the red light valve
108
R, a green light valve
108
G interposed between the green separating mirror
103
G and the surface
104
G of the color synthesizing prism
104
, a green lens
109
G disposed between the green separating mirror
103
G and the green light valve
108
G, a blue light valve
108
B interposed between the reflecting mirror
105
B and the surface
104
B of the color synthesizing prism
104
, and a blue lens
109
B interposed between the reflecting mirror
105
B and the blue light valve
108
B.
The video display apparatus further includes a projector lens
110
disposed in an opposing relationship to a still further surface of the color synthesizing prism
104
parallel to the surface
104
G.
In the conventional video display apparatus having the configuration described above, a white light lamp such as a xenon lamp or a metal halide lamp is used for the light source
101
. Light emitted from the light source
101
is reflected by the reflecting plate
100
and is then introduced into the red separating mirror
103
R through the integrator
102
after ultraviolet rays and infrared rays are removed from the light by a cut filter apparatus not shown. Of the light introduced into the red separating mirror
103
R, a red light component is reflected by the red separating mirror
103
R and the reflecting mirror
105
R and then passes through the red lens
109
R and the red light valve
108
R so that it is introduced into the color synthesizing prism
104
. The other color light components of the light introduced into the red separating mirror
103
R than the red light pass through the red separating mirror
103
R and are introduced into the green separating mirror
103
G.
Of the light introduced into the green separating mirror
103
G, a green light component is reflected by the green separating mirror
103
G and introduced into the color synthesizing prism
104
through the green lens
109
G and the green light valve
108
G. The other color light component of the light introduced into the green separating mirror
103
G than the green light passes through the green separating mirror
103
G and is introduced into the reflecting mirror
103
B through the optical path length adjusting lens
106
.
The light introduced into the reflecting mirror
103
B, that is, the blue light component, is reflected by the reflecting mirror
103
B and passes through the optical path length adjusting lens
107
, whereafter it is reflected further by the reflecting mirror
105
B and then introduced into the color synthesizing prism
104
through the blue lens
109
B and the blue light valve
108
B.
The color light components introduced into the color synthesizing prism
104
are synthesized by the color synthesizing prism
104
and projected onto a screen of the transmission type or the reflection type through the projector lens
110
.
In the conventional video display apparatus, since single kind of light source is used by itself for the light source
101
, wavelengths included in light emitted from the light source
101
are somewhat one-sided, and therefore, it is difficult to obtain a well-balanced light amount ratio of the three color light components separated by the color separating mirrors
103
R and
103
G and the reflecting mirror
103
B. Therefore, it is difficult to augment the color reproducibility of the conventional video display apparatus. Further, since a white light lamp which is used in the conventional video display apparatus exhibits difficulty in adjustment of the brightness with a high degree of accuracy and emits light with a fixed brightness, it is difficult to adjust the brightness for each of the color light components of red, green and blue independently of each other.
Further, in the conventional video display apparatus, a luminous flux emitted from a white light lamp used as the light source
101
has a circular cross section. In contrast, the light valves
108
R,
108
G and
108
B upon which the light is irradiated normally have a rectangular shape. Accordingly, in order to introduce the light uniformly to the light valves
108
R,
108
G and
108
B, the diameter of the luminous flux incident to each light valve is set greater than the length of a diagonal line of each light valve. Consequently, there is a problem that the irradiation efficiency of the light irradiated from the light source
101
is low.
Thus, another video display apparatus has been proposed which uses a plurality of lamps for its light source or a plurality of semiconductor light emitting elements such as light emitting diodes or laser diodes for each of the three primary colors.
FIG. 2
shows an XY chromaticity diagram indicating color reproduction ranges by a phosphor of a CRT (Cathode Ray Tube), a video display apparatus which uses a light emitting diode and a display apparatus of the NTSC (National Television System Committee) system. It can be seen from the XY chromaticity diagram that, where the light emitting diode is used for the light source, the color reproduction range is greater than the color reproduction range of the phosphor of a CRT or a display apparatus of the NTSC system.
However, since rays of light emitted from a plurality of light sources have angles, non-axial light from outside an optical axis is produced. If non-axial light is included in the light emitted from the light sources, it is difficult to irradiate the light uniformly upon a light valve. Further, since the light is irradiated to the outside of the light valve, also the irradiation efficiency of light is deteriorated disadvantageously.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a video display apparatus wherein, where a plurality of kinds of white light lamps or a plurality of semiconductor light emitting elements having a good color purity are used for a light source, light emitted from the light source can be introduced uniformly and efficiently to a light valve.
In order to attain the
Cariaso Alan
Maioli Jay H.
Sony Corporation
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