Television – Camera – system and detail – With single image scanning device supplying plural color...
Reexamination Certificate
1998-03-17
2001-12-11
Garber, Wendy R. (Department: 2612)
Television
Camera, system and detail
With single image scanning device supplying plural color...
C348S273000
Reexamination Certificate
active
06330029
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to color filter arrays for image sensors.
BACKGROUND OF THE INVENTION
In electronic color imaging, it is desirable to simultaneously capture image data in three color planes, usually red, green and blue. When the three color planes are combined, it is possible to create high-quality color images. Capturing these three sets of image data can be done in a number of ways. In electronic photography, this is sometimes accomplished by using a single two dimensional array of sensors that are covered by a pattern of red, green and blue filters. This type of sensor is known as a color filter array or CFA. Below is shown the red (R), green (G) and blue (B) pixels as are commonly arranged on a CFA sensor.
When a color image is captured using a CFA, it is necessary to interpolate the red, green and blue values so that there is an estimate of all three color values for each sensor location. Once the interpolation is done, each picture element, or pixel, has three color values and can be processed by a variety of known image processing techniques depending on the needs of the system. Some examples of the reasons for processing are to do image sharpening, color correction or half toning.
The diagram below shows how red green and blue pixels can be arranged in a particular color filter array pattern, hereinafter referred to as the Bayer color filter array. For a more detailed description see U.S. Pat. No. 3,971,065 issued Jul. 20, 1976 to Bayer.
G
R
B
G
In commonly assigned U.S. Pat. No. 5,596,367 issued Jan. 21, 1997, incorporated by reference, adaptive methods of calculating green pixel values at pixels where green is not directly measured is described. These methods rely on algorithmically selecting one or two ways to calculate the missing green values. After determining the missing green values, the red minus green color difference values are computed at red pixel sites and the blue minus green color difference values are computed at blue pixel sites. The missing values for each color difference are computed by simple linear interpolation. Because the red, green, and blue CFA filters absorb two thirds of the incident light, such CFA sensors tend to be photometrically slow. Especially in low light situations, it would be better to use subtractive CFA filters such as cyan, magenta, yellow, and green. It would also be desirable to have a CFA pattern that permits adaptive interpolation of the luminance value (analogous to green) and permits for adaptive interpolation of both color difference values as well.
SUMMARY OF THE INVENTION
It is an object of the present invention is to provide a color filter array pattern which provides signals which can be efficiently processed since the color filter array uses a 2×2 repeating pattern.
It is a further object of the invention to have a CFA pattern which has at least two methods of luminance interpolation as well as two methods for each chrominance value to thereby provide improved interpolation for both luminance and chrominance.
This object is achieved in a color filter array for an image sensor which has a plurality of pixels, the color filter array comprising:
(a) a plurality of color pixel kernels, with each kernel having the plurality of pixels arranged in the following pattern
A
C
D
B
wherein:
A and B are companion colors; and
C and D are companion colors.
ADVANTAGES
An advantage of the present invention is that the color filter array pattern uses kernels with only four pixels and this facilitates calculations and interpolation.
A feature of this invention is that it permits non-linear interpolation of both luminance values and chrominance values, regardless of location within the CFA pattern.
Another advantage of the present invention is that the same processing can be used irrespective of the location of the pixels in the CFA.
Another advantage of the present invention is that it facilitates the use of the smallest kernel of CFA pixels can be used to provide a high quality estimate of luminance.
REFERENCES:
patent: 3971065 (1976-07-01), Bayer
patent: 4630106 (1986-12-01), Morimura et al.
patent: 4768084 (1988-08-01), Noda et al.
patent: 5028547 (1991-07-01), Iizuka et al.
patent: 5418564 (1995-05-01), Aoki et al.
patent: 5419990 (1995-05-01), Wake et al.
patent: 5596367 (1997-01-01), Hamilton, Jr. et al.
patent: 5631703 (1997-05-01), Hamilton, Jr. et al.
patent: 5786588 (1998-07-01), Takahashi
patent: 5880781 (1999-03-01), Udagawa et al.
patent: 5966174 (1999-10-01), Yamamoto et al.
Adams James E.
Hamilton John F.
Orlicki David M.
Eastman Kodak Company
Garber Wendy R.
Owens Raymond L.
Tillery Rashawn N.
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