Optics: image projectors – Composite projected image – Multicolor picture
Reexamination Certificate
2001-12-31
2003-03-25
Dowling, William (Department: 2851)
Optics: image projectors
Composite projected image
Multicolor picture
C353S121000, C348S743000
Reexamination Certificate
active
06536904
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to display systems and particularly to single or dual-panel spatial light modulator sequential color systems.
2. Description of the Related Art
Sequential color display systems, like single-chip micromirror systems, temporally filter the illumination source into primary colors. These typically has been implemented using a spinning wheel that has dichroic filter segments along the outer diameter of the wheel
10
, as illustrated in
FIG. 1
a.
For single-panel architectures, the primary color filter set of red
11
, green
12
, and blue
13
(R-G-B) light is used in every video display frame. Optionally, as shown in
FIG. 1
b,
two-panel optical architectures may use a color splitting prism or dichroic mirror
18
to provide red light (R) to a first modulator panel, and a color filter wheel
15
with yellow
16
(Y) and magenta
17
(M) filters to alternately provide blue (B) and green (G) light to a second modulator panel.
Sequential display systems sometimes add a white (clear) segment to the color wheel
20
, as shown in
FIG. 2
a
and disclosed in U.S. Pat. No. 5,233,385, to improve the sequential color efficiency by applying a gain function to the luminance portion of the signal and displaying some portion of the luminance signal during the white segment time, in order to provide a brighter picture on the display. In operation, the white energy (luminance) in each pixel is gained-up by a certain factor and if the R-G-B signal levels saturate, then energy is subtracted from the R-G-B channels and shifted to the white segment. In order to maximize brightness, the outputs of the R-G-B channels are also maximized for a full-white signal. As shown, the color wheel
20
consists of red (R)
21
, green (G)
22
, blue (B)
23
, and clear or white (W)
24
segments.
FIG. 2
b
shows a color filter wheel
25
with a white segment used in a two-DMD color projector system. In this case, the color filter wheel
25
consists of yellow (Y)
27
, magenta (M)
28
, and white (W)
29
segments.
Sequential color systems exhibit an undesirable characteristic when eye motion occurs in localized area of black and white pixels in a given image. For relatively slow moving objects, leading edges appear to have a color hew to them, which corresponds to the first color in the color sequence while trailing edges appear to a have color hew of the last color in the color sequence. In scenes that induce rapid eye motion, a color rainbow effect is created that has the appearance of color ghost images in these black and white areas of the picture. In the past, this undesirable color separation has been addressed by means of faster sequencing of the colors; either by faster rotation of the color wheel or by splitting the color wheel filters into multiple sets of R-G-B segments. However, both of these approaches introduce negative factors, such as: (1) audible noise and less mechanical stability when operating the color wheel at higher speeds, (2) decreased efficiency (loss of brightness) due to additional color wheel spokes when adding additions filter segments, and (3) higher cost and (4) increased temporal artifacts (pulse width modulation noise).
There is a recognized need for a method which addresses the color separation problem discussed above in a more elegant way without introducing the new negative factors discussed immediately here above. The invention disclosed herein addresses this need in both a method and an apparatus.
SUMMARY OF THE INVENTION
This invention discloses the method and apparatus for reducing the color separation in a sequential color display system. The disclosed approach adds a white (clear) segment to the color filtering system and applying an algorithm, which separates the luminance channel as much as possible into this white segment. As a result, in the case of a black-and-white image where color separation is most visible, color segments will have a minimal amount of energy in them, thereby reducing the color separation effect.
The algorithm uses a constant (&agr;), defined as the ratio of the white segment time to the smallest color segment time, to control the process of transferring as much of the energy as possible from the colored segments into the white segment.
The disclosed method extends the process to dynamically adjust the color segment (R
gain
, G
gain
, and B
gain
) values on a pixel-by-pixel basis, such that colored areas of the image are maximized for brightness and black-and-white areas are maximized for minimum color separation. This allows a trade-off to be made between maximum brightness for the color areas and minimum color separation for the black-and-white areas of the image.
REFERENCES:
patent: 5592188 (1997-01-01), Doherty et al.
patent: 6054832 (2000-04-01), Kunzman et al.
patent: 6226054 (2001-05-01), Morgan et al.
patent: 6256425 (2001-07-01), Kunzman
patent: 6324006 (2001-11-01), Morgan
patent: 6392717 (2002-05-01), Kunzman
patent: 6406148 (2002-06-01), Marshall et al.
Brady III Wade James
Brill Charles A.
Dowling William
Telecky , Jr. Frederick J.
Texas Instruments Incorporated
LandOfFree
Reduced color separation white enhancement for sequential... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Reduced color separation white enhancement for sequential..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Reduced color separation white enhancement for sequential... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3033935