Television – Video display – Color sequential
Reexamination Certificate
1999-08-06
2004-01-06
Miller, John (Department: 2614)
Television
Video display
Color sequential
C348S655000, C348S835000, C359S506000
Reexamination Certificate
active
06674489
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an image display, and particularly to an image display which performs color reproduction by using color filters.
2. Description of the Background Art
Recently, many displays which reproduce color images by separating light from a light source into N kinds of colors by using color filters and projecting the lights separated into N colors onto a screen are appearing. The number N is a positive integer. Usually N is equal to three, and lights separated into three colors of red, green and blue (hereinafter referred to as R, G, B) through color filters are projected to reproduce a color image.
The displays which reproduce color images by using lights color-separated by filters are roughly classified into two types according to structure. One is the time-division color projection system and the other is the simultaneous color projection system. The time-division color projection system and the simultaneous color projection system will now be described about a structure in which lights separated into the three colors R, G, B through color filters are projected to reproduce a color image.
In the time-division color projection system, lights separated into N kinds of colors through color filters are projected in order in a time-division manner within a single image frame to reproduce a color image. When reproducing a color image by projecting lights separated into the three colors R, G, B through color filters, the lights separated into R, G, and B are projected in order in a time-division manner to reproduce a color image.
In the simultaneous color projection system, lights separated into N kinds of colors through color filters are simultaneously projected to reproduce a color image. For example, when reproducing a color image by projecting lights separated into the three colors R, G, B, the lights separated into R, G, B through color filters are simultaneously projected to reproduce a color image.
FIG. 15
is a diagram showing an example of a color image display of the time-division color projection system using a light valve. The light valve is an element for modulating light, which may be a DMD, liquid crystal, etc. As shown in
FIG. 15
, the time-division color projection system color image display has a light source
101
, a color disk
102
, a light valve
103
, a screen
104
, and a signal processing unit
105
. The color image display of
FIG. 15
reproduces a color image by projecting lights separated into the three colors R, G, B.
The operation of the time-division color projection system will now be described referring to FIG.
15
. Image data is inputted to the signal processing unit
105
. The signal processing unit
105
generates control signals for the color disk
102
and the light valve
103
from the input image data and supplies the control signals to the color disk
102
and the light valve
103
.
The light emitted from the light source
101
enters a part of the color disk
102
. The color disk
102
is divided into three areas: a filter transmitting red (R) light, a filter transmitting green (G) light, and a filter transmitting blue (B) light. The color disk
102
is rotating while controlled by the control signal from the signal processing unit
105
and the filter located in the position the light from the light source
101
strikes is changed in a time-division manner. Thus the light from the light source
101
is color-separated into R, G, B lights in a time-division manner by the color disk
102
. The lights color-separated into R, G, and B lights at the color disk
102
in a time division manner impinge on the light valve
103
.
The R, G, and B lights incident upon the light valve
103
are modulated by the light valve
103
according to the control signal from the signal processing unit
105
and projected onto the screen
104
.
Next, the simultaneous color projection system will be described.
FIG. 16
is a diagram showing an example of a color image display of the simultaneous color projection system using a light valve. As shown in
FIG. 16
, the simultaneous color projection system color image display has light sources
101
a
to
101
c
, light valves
103
a
to
103
c
, a screen
104
, a signal processing unit
105
, a filter transmitting red light
106
a
, a filter transmitting green light
106
b
, and a filter transmitting blue light
106
c
. The color image display of
FIG. 16
reproduces a color image by projecting the lights separated into the three colors R, G, B.
The operation of the simultaneous color projection system will now be described referring to FIG.
16
. Image data is inputted to the signal processing unit
105
. The signal processing unit
105
generates control signals for the light valves
103
a
to
103
c
from the input image data and supplies the control signals to the light valves
103
a
to
103
c.
The light emitted from the light source
101
a
enters the color filter
106
a
. The color filter
106
a
has a property of transmitting red light, and the light from the light source
101
a
is color-separated to R light at the color filter
106
a
. The R light color-separated at the color filter
106
a
impinges upon the light valve
103
a.
Similarly, the light from the light
101
b
is color-separated to G light at the color filter
106
b
and impinges upon the light valve
103
b
. The light from the light source
101
c
is color-separated to B light at the color filter
106
c
and impinges upon the light valve
103
c.
The R, G, and B lights incident upon the light valves
103
a
,
103
b
, and
103
c
are modulated at the light valves
103
a
,
103
b
and
103
c
according to the control signals from the signal processing unit
105
and projected onto the screen
104
.
As described above, a display which color-separates light from light source using color filters and reproduces a color image using the color-separated lights can be realized by the time-division color projection system or the simultaneous color projection system. The two systems are common in that they color-separate the light emitted from the light source through color filters.
Now a color image display which reproduces a color image with lights generally separated into N colors will be considered. The spectral emissivity of the light emitted from the light source is shown as E(&lgr;) and the spectral transmittances of the N color filters for color-separating the light from the light source are shown as fi(&lgr;). Where i=1, 2, . . . , N. In this case, the spectral distributions ci(&lgr;) of the N-color lights Ci color-separated by the N color filters can be expressed by equation (1) below.
ci
(&lgr;)=
E
(&lgr;)×
fi
(&lgr;) Eq.(1)
From equation (1), the spectral distributions ci(&lgr;) of the lights Ci separated into N colors are represented as the product of the spectral emissivity E(&lgr;) of the light emitted from the light source and the spectral transmittance fi(&lgr;) of the color filters. Accordingly, to efficiently utilize the light emitted from the light source, the characteristic of the spectral emissivity E(&lgr;) of the light emitted from the light source must be taken into consideration when determining the spectral transmittances fi(&lgr;) of the color filters.
Now suppose a light source S having such spectral emissivity as shown in FIG.
17
. In
FIG. 17
, the vertical axis shows the relative intensity of light emitted from the light source and the horizontal axis shows the wavelength. The spectral emissivity of the light source S shown in
FIG. 17
has intensive radiations in the two wavelength regions a and b. Such a spectral emissivity characteristic as has intensive radiations at particular wavelengths is shown by a super high pressure mercury lamp, a xenon lamp, etc.
Now we consider the color separation of light from a light source S through color filters.
FIG. 18
is a diagram showing an example of spectral transmittance characteristic of a color filter F used in the color separation.
FIG. 18
shows the spectral transmi
Kagawa Shuichi
Shikama Shinsuke
Sugiura Hiroaki
Suzuki Yoshiteru
Teramoto Kohei
Birch & Stewart Kolasch & Birch, LLP
Miller John
Mitsubishi Denki & Kabushiki Kaisha
Yenke Brian
LandOfFree
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