Illumination – Light source and modifier – Including selected wavelength modifier
Reexamination Certificate
2001-05-25
2004-06-29
Cariaso, Alan (Department: 2875)
Illumination
Light source and modifier
Including selected wavelength modifier
C362S324000, C362S284000, C348S743000, C348S748000, C353S031000
Reexamination Certificate
active
06755554
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a display device using a spatial light modulator (SLM) or light valve which works at a considerably high speed and, more particularly, to a color wheel assembly and a field sequential color display device using the same, a color wheel unit and a field sequential color display device using the same, and a field sequential color display device, to display colors in a time-multiplexing and color sequential manner.
BACKGROUND OF THE INVENTION
In recent years, attention has been increasingly focused on large screen displays such as home theaters and presentations, and projectors are recently being commercialized which use a small reflective light valve of a liquid crystal on silicon (hereinafter, referred to as LCOS) in which a switching element, a reflection electrode or the like is formed on a silicon substrate or a digital micromirror device (hereinafter, referred to as DMD), and enlargedly project a display image with a projection lens to obtain a large screen display image.
The LCOS is one of the SLMs, and it has reflection pixels in a form of matrix, and can switch displays at a high speed using a video signal. In order to display moving pictures at a video rate, it is necessary that video of 60 frames can be displayed within one field. For that purpose, the liquid crystal response speed of at least 1/60=16.7 msec or lower is required. Further, in order to display at least three colors (RGB) during that time, a response speed of 5.6 msec is required. As examples of such a high-speed response liquid crystal, there are a ferroelectric liquid crystal, an antiferroelectric liquid crystals, an OCB (optically Compensated Bend) liquid crystal and the like in the OCR liquid crystal, a Bend orientation cell is used to self-compensate changes in the visibility angle direction using birefringence of the liquid crystal, and when this liquid crystal is combined with a negative optical compensation film, a wider visibility angle is realized, as well as a high-speed response is enabled.
The DMD is one of the SLMs, and is mainly used as a projection-type display. The DMD has hundreds of thousands or one million or more extremely minute mirrors on one chip, each of the mirrors corresponding to one pixel. ON/OFF of the DMD is controlled by inclining these mirrors to change the reflection angles of beams which are incident on the mirrors. For that purpose, the respective mirrors are mounted to one or more hinges which are mounted on a supporting post, and are separated from a control circuit situated below by an air gap. This control circuit applies static electricity, which selectively inclines the respective mirrors. When this is applied to a display, image data are loaded on a memory cell of the DMD, and the mirrors are inclined on the basis of these data to reflect light toward the ON direction or away from the ON direction.
As methods adopted in the projectors, when classified according to the number of SLMs required in the projector, a single-panel type and a three-panel type are mainly used. As an example of the three-panel-type projectors, there is one which modulates light beams of respective colors, which has been subjected to the color separation, by the corresponding SLMs, respectively, and then performs the color composition while projecting the light on a screen. In this method, three SLMs are used in parallel, the respective being used for red (R), green (G), and blue (B). On the other hand, in the single-panel-type projector, only one SLM is used, and R, G and B light beams are modulated successively in a time-multiplexing manner, or spatially in units of area or pixel, while using a single-panel SLM. Accordingly, in the single-panel-type projector which requires only one SLM, requests to hardware relating to the SLM are only one-third of those in the three-panel-type projector which requires three SLMs. This is not restricted to the projectors, but applies to all color display devices using the SLMs.
Hereinafter, the color display device using the single-panel projector is described.
As an example of the color display device using the single-panel projector, there is a time-multiplexing color sequential type color display device utilizing a time-multiplexing color mixture. In this time-multiplexing color sequential method, the pixels have red, green and blue values, respectively, and during each frame period, the pixels in the frame are addressed successively according to red, blue, and then green data. On the other hand, filters of the same colors as these colors are positioned in the form of a disk, a color wheel having at least three different color regions is synchronized with these data, and data corresponding to the respective colors are displayed by the SLM. At this time, the band of light incident on the SLM is controlled by the color wheel. As described above, the time-multiplexing field sequential color display device enables color display in a time-multiplexing manner and, when the time-multiplexing rate is higher than the standard display speed of 60 images/sec, the images are perceived by the eyes to have original colors.
The above-mentioned prior art field sequential color display device using the color filter is described with reference to FIG.
36
.
FIG. 36
is a diagram schematically illustrating an example of the prior art field sequential color display device using the color wheel. As shown in
FIG. 36
, the field sequential color display device comprises a lamp
1001
, an ellipsoidal mirror
1002
, an UV-IR cut-off filter
1003
, a color wheel
1004
, a condensing lens
1005
, a field lens
1006
, a reflective LCOS
1007
, and a projection lens
1008
.
The lamp
1001
is a discharging-type high output lamp such as a xenon lamp, a metal halide lamp, and an extra-high pressure mercury lamp.
The reflective LCOS
1007
is one of the SLM.
The color wheel
1004
is preferably situated in a position where beams are condensed the most. This is because the SLM should be turned off to prevent color mixture, while the color wheel is being rotated and a beam spot is passing through the boundary of the different color filters, and the shorter the OFF time is, the higher the temporal opening ratio is, whereby brighter displays are enabled. Therefore, it is preferable that the condensation spot on the color filter should be smaller to miniaturize the color wheel, otherwise a color wheel having a larger outer diameter is required, resulting in a considerably large size of the entire system.
The operation of the so-constructed prior art field sequential color display device is described. The lamp
1001
is positioned approximately in a focus position of the ellipsoidal mirror
1002
as a concave mirror, so that the emitted white light beams are condensed by the ellipsoidal mirror
1002
on the color filter of the color wheel
1004
. The UV-IR cut-off filter
1003
filters out ultraviolet and infrared rays of the light emitted from the lamp
1001
. The color wheel
1004
comprises red, blue, and green color filters which are positioned in the form of a disk and, in synchronization with the filtering of beams by the respective color filters, the LCOS
1007
displays image frames of the beam color. Normally, the color wheel
1004
is rotated one revolution per image frame in 1/60 sec, or at 3600 rpm. The condensing lens
1005
efficiently condenses light which is transmitted through the color wheel
1004
, and irradiates the LCOS
1007
. The field lens
1006
is used for condensing light which is transmitted through the LCOS
1007
on the projection lens
1008
.
In this prior art field sequential color display device, there are at least three color sub-frames during one frame frequency, the sub-frames being red, green and blue, respectively. The LCOS
1007
switches display images at a considerably high speed for the respective colors, and modulated beams of respective colors are enlargedly projected on a screen (not shown) by using the projection lens
1008
. Since videos of the respective colors (R, G and B) are
Aruga Shigeru
Ohmae Hideki
Sakaguchi Hirokazu
Shimose Hisatoshi
Tanabe Kazunori
Cariaso Alan
Negron Ismael
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