Image analysis – Image transformation or preprocessing – Changing the image coordinates
Reexamination Certificate
2000-11-29
2004-12-28
Tran, Phuoc (Department: 2621)
Image analysis
Image transformation or preprocessing
Changing the image coordinates
C382S162000
Reexamination Certificate
active
06836572
ABSTRACT:
INCORPORATION BY REFERENCE
The disclosures of the following applications are herein incorporated by reference:
Japanese Patent Application No. 10-151278 filed Jun. 1, 1998
Japanese Patent Application No. 10-277166 filed Sep. 30, 1998
Japanese Patent Application No. 11-145473 filed May 25, 1999
Japanese Patent Application No. 2000-186367 filed Jun. 21, 2000
PCT Application No. PCT/JP99/02887 filed May 31, 1999
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an interpolation processing apparatus that implements interpolation processing for obtaining an interpolation quantity which is equivalent to color information corresponding to a first color component for each vacancy in an image generated by an image-capturing sensor having a plurality of lattice points and a plurality of vacancies in a two-dimensional array with the lattice points each outputting color information corresponding to the first color component and the vacancies each outputting color information corresponding to a second color component or a third color component without outputting color information corresponding to the first color component, and it also relates to a recording medium for recording an interpolation processing program utilized to execute the interpolation processing on a computer.
2. Description of the Related Art
Some electronic still cameras utilize a single image-capturing sensor to generate image signals of a color image. Such an image-capturing sensor may be constituted by arranging color filters in three colors, i.e., R, G and B (red, green and blue) in a Bayer array, as illustrated in FIG.
22
A. With regard to the green color (G), the image-capturing sensor can be regarded as being composed of lattice points each constituted of a pixel that outputs green color and vacancies each constituted of a pixel which does not output green color, as shown in FIG.
22
B.
In this type of electronic still camera, it is necessary to implement interpolation processing in order to obtain green color information at each vacancy. For this application, an interpolation processing method in which an interpolation quantity is calculated by judging the direction along which a vacancy undergoing the interpolation processing (hereafter referred to as an interpolation target vacancy) manifests a high degree of spatial similarity and using the color information at lattice points adjacent to the interpolation target vacancy along the direction has been proposed in the prior art.
U.S. Pat. Nos. 5,629,734 and 5,652,621 each disclose a technology for calculating similarity degrees along a plurality of directions to be used when judging the direction manifesting a pronounced similarity.
For instance, if color information is provided around the interpolation target vacancy expressed as “A
1
, G
2
, A
3
, G
4
, A
5
” (with A
1
, A
3
and A
5
each representing color information corresponding to the same-color component as that at the interpolation target vacancy and G
2
and G
4
each representing color information at a lattice point), a similarity degree C of the interpolation target vacancy along the direction in which the lattice point outputting G
2
and the lattice point outputting G
4
is set is calculated through the following expression C-1 in the technology disclosed in U.S. Pat. No. 5,629,734, whereas the similarity degree C is calculated through expression C-2 in the technology disclosed in U.S. Pat. No. 5,652,621.
C=|−A
1
+2
A
3
−
A
5
|+|
G
2
−
G
4
| expression C-1
C=|−A
1
+2
A
3
−
A
5
|+|
G
2
−
G
4
|+|−
G
2
+2(
A
3
+bias)−
G
4
| expression C-2
with “bias” in expression C-2 representing a value satisfying
bias=(bias′+
A
1
−
G
1
)/2 expression C-3,
in which “bias′” represents the bias used to calculate the similarity degree of A
1
and G
1
indicates the interpolation quantity ascertained through the interpolation processing implemented on A
1
.
In the technology disclosed in U.S. Pat. No. 5,629,734, the results obtained by comparing color information corresponding to a single color component at every other pixel (hereafter referred to as same-color similarity components: correspond to |−A
1
+
2
A
3
−A
5
| and |G
2
−G
4
| in expression C-1) are added and the sum is used as the similarity degree of the interpolation target vacancy. Thus, since similarity degree in an image which changes in smaller increments than the intervals (equivalent to twice the intervals between individual pixels) over which the same-color information is provided (an image with a high spatial frequency) cannot be accurately calculated through the technology disclosed in U.S. Pat. No. 5,629,734, the judgment with regard to the direction manifesting a pronounced similarity cannot be made with a high degree of accuracy, thereby presenting a high likelihood of color artifacs (or false color).
Through the technology disclosed in U.S. Pat. No. 5,652,621, on the other hand, in which the similarity degree is calculated through expression C-2 which incorporates the results of a comparison of color information at adjacent pixels (hereafter referred to as a “different-color similarity component”: correspond to |−G
2
+2(A
3
+bias)−G
4
| in expression C-2) with the same-color similarity components (correspond to |−A
1
+2A
3
−A
5
| and |G
2
−G
4
| in expression C-2), the occurrence of color artifacts can be reduced in an image with a high spatial frequency.
However, since the results of a comparison of color information corresponding to only two colors set on a single straight line (color information corresponding to the same-color component as that at the interpolation target vacancy and color information at a lattice point) are used as a different-color similarity component in the technology disclosed in U.S. Pat. No. 5,652,621, the similarity degree cannot be calculated with accuracy in an area where the color tone changes (an image in which the ratio of the color information corresponding to the three colors changes) as in a border area in a natural image and the influence of the different-color similarity components manifests to a greater degree than the influence of the same-color similarity components even when the same-color similarity components are calculated accurately, which presents difficulty in judging the direction along which a pronounced similarity manifests with accuracy, resulting in a high likelihood of occurrence of color artifacts.
In other words, when interpolating an image which includes an image area with a high spatial frequency and an image area where the color tone changes through either of the technologies disclosed in the U.S. patent specifications mentioned above, the similarity degrees in the two image areas in the image cannot be calculated accurately, resulting in the color artifacts occurring in either image area becoming conspicuous to disrupt the harmony of the entire image.
In addition, since the different-color similarity component is calculated by using G
1
(interpolation quantity at A
1
) and bias′ (bias at A
1
) in the technology disclosed in U.S. Pat. No. 5,652,621, once a similarity component is calculated erroneously, the error affects similarity components to be calculated subsequently, which presents a concern that the range over which color artifacts occur may expand.
In other words, in the worst scenario, by implementing interpolation processing through the technology disclosed in U.S. Pat. No. 5,652,621, the quality of the image may even become worse.
SUMMARY OF THE INVENTION
Accordingly, an object of the present invention is to provide an interpolation processing apparatus capable of calculating an interpolation quantity with a high degree of accuracy by accurately judging the direction along w
Ishiga Kenichi
Utagawa Ken
Nikon Corporation
Oliff & Berridg,e PLC
Tran Phuoc
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