Image processing apparatus and method, recording medium, and program

• US 20050089241A1
• Filed: 08/19/2004
• Published: 04/28/2005
• Est. Priority Date: 09/05/2003
• Status: Active Grant

• Current Assignee: Sony Corporation (Sony Group Corp.)
• Original Assignee: Sony Corporation (Sony Group Corp.)
• Inventors: Sato, Nobuyuki, Okada, Miyuki, Kawanishi, Isao, Nakajima, Ken
• Granted Patent: US 7,460,728 B2
• Time in Patent Office: Days
• US Class Current: 382/274
• CPC Class Codes: H04N 23/69 Control of means for changing angle of the field of view, e.g. optical zoom objectives or electronic zooming
• CPC Class Codes: H04N 23/76 by influencing the image signals
• CPC Class Codes: H04N 23/81 for suppressing or minimising disturbance in the image signal generation
• CPC Class Codes: H04N 9/646 for image enhancement, e.g. vertical detail restoration, cross-colour elimination, contour correction, chrominance trapping filters

Abstract

For each pixel read from an imaging device, a horizontal counter value and a vertical counter value corresponding to the pixel are supplied from a signal generator to a distance computation section via an optical-axis-center coordinate setting section and an up-and-down and right-and-left weighting section. In the distance computation section, the distance to the optical-axis center is computed, and correction coefficients for the zoom wide end and for the zoom tele end, which correspond to the distance, are obtained by look-up tables. The two obtained correction coefficients are blended at a mixture ratio determined by a blend ratio setting section. The blended shading correction coefficients are gain adjusted by a gain adjustment section, after which they are supplied to a correction section. As a result, a correction corresponding to the distance to the optical-axis-center position is performed on the signal of each pixel supplied from an imaging section.

Claims

1. An image processing apparatus for correcting shading of a captured image, said image processing apparatus comprising:

a first distance computation section for computing the distance from the image-plane center to each pixel by multiplying the distance by a distance gain;

an obtaining section for obtaining a correction value for correcting the shading of said image on the basis of said distance computed by said first distance computation section; and

a correction section for correcting the signal of each of said pixels on the basis of said correction value obtained by said obtaining section.

2. The image processing apparatus according to claim 1, wherein said obtaining section obtains a plurality of said correction values.

3. The image processing apparatus according to claim 2, further comprising:

a mixture-ratio setting section for setting the mixture ratio of said plurality of correction values obtained by said obtaining section; and

a mixing section for mixing said plurality of correction values on the basis of said mixture ratio set by said mixture-ratio setting section,

wherein said correction section corrects the signal of each of said pixels on the basis of said correction value mixed by said mixing section.

4. The image processing apparatus according to claim 3, wherein said mixture-ratio setting section sets said mixture ratio on the basis of the lens zoom position, the focus position, the image height, the aperture stop value, the exit pupil position, and the amount of strobe light emission.

5. The image processing apparatus according to claim 1, further comprising a gain adjustment section for adjusting the gain of said correction value obtained by said obtaining section.

6. The image processing apparatus according to claim 1, further comprising, when said image is composed of three colors of a G pixel, an R pixel, and a B pixel:

a second distance computation section for computing the distance from the image-plane center to each pixel by multiplying the distance by a distance gain in accordance with said G pixel;

a first distance balance gain correction section for multiplying the distance gain in which said G pixel is used as a reference by the distance balance gain of said R pixel; and

a second distance balance gain correction section for multiplying the distance gain in which said G pixel is used as a reference by the distance balance gain of said B pixel.

7. The image processing apparatus according to claim 1, further comprising, when said image is composed of four colors of a Gr pixel, an R pixel, a B pixel, and a Gb pixel, or four colors of an E pixel, an R pixel, a B pixel, and a G pixel:

a second distance computation section for computing the distance from the image-plane center to each pixel by multiplying the distance by a distance gain in accordance with said Gb pixel or said G pixel;

a first balance gain correction section for multiplying the distance gain in which said Gb pixel or said G pixel is used as a reference by the distance balance gain of said R pixel;

a second balance gain correction section for multiplying the distance gain in which said Gb pixel or said G pixel is used as a reference by the distance balance gain of said B pixel; and

a third balance gain correction section for multiplying the distance gain in which said Gb pixel or said G pixel is used as a reference by the distance balance gain of said Gr pixel or said E pixel.

17. The image processing apparatus according to claim 1, further comprising a conversion section for performing a conversion, corresponding to thinning-out information of the image, on the distance computed by said distance computation section.

18. The image processing apparatus according to claim 1, wherein said obtaining section obtains said correction value by referring to a look-up table.

19. The image processing apparatus according to claim 1, wherein said obtaining section computes said correction value by computations.

8. An image processing method for use with an image processing apparatus for correcting shading of a captured image, said image processing method comprising:

a first distance computation step of computing the distance from the image-plane center to each pixel by multiplying the distance by a distance gain;

an obtaining step of obtaining a correction value for correcting the shading of said image on the basis of said distance computed in said first distance computation step; and

a correction step of correcting the signal of each of said pixels on the basis of said correction value obtained in said obtaining step.

9. The image processing method according to claim 8, further comprising, when said image is composed of three colors of a G pixel, an R pixel, and a B pixel:

a second distance computation step of computing the distance from the image-plane center to each pixel by multiplying the distance by a distance gain in accordance with said G pixel;

a first distance balance gain correction step of multiplying the distance gain in which said G pixel is used as a reference by the distance balance gain of said R pixel; and

a second distance balance gain correction step of multiplying the distance gain in which said G pixel is used as a reference by the distance balance gain of said B pixel.

10. The image processing method according to claim 8, further comprising, when said image is composed of four colors of a Gr pixel, an R pixel, a B pixel, and a Gb pixel, or four colors of an E pixel, an R pixel, a B pixel, and a G pixel:

a second distance computation step of computing the distance from the image-plane center to each pixel by multiplying the distance by a distance gain in accordance with said Gb pixel or said G pixel;

a first distance balance gain correction step of multiplying the distance gain in which said Gb pixel or said G pixel is used as a reference by the distance balance gain of said R pixel;

a second distance balance gain correction step of multiplying the distance gain in which said Gb pixel or said G pixel is used as a reference by the distance balance gain of said B pixel; and

a third distance balance gain correction step of multiplying the distance gain in which said Gb pixel or said G pixel is used as a reference by the distance balance gain of said Gr pixel or said E pixel.

11. A recording medium having recorded thereon a computer-readable program executable to perform image processing of an image processing apparatus for correcting shading of a captured image, the program comprising:

a first distance computation step of computing the distance from the image-plane center to each pixel by multiplying the distance by a distance gain;

an obtaining step of obtaining a correction value for correcting the shading of said image on the basis of said distance computed in said first distance computation step; and

a correction step of correcting the signal of each of said pixels on the basis of said correction value obtained in said obtaining step.

12. The recording medium having recorded thereon a computer-readable program according to claim 11, said program further comprising, when said image is composed of three colors of a G pixel, an R pixel, and a B pixel:

a second distance computation step of computing the distance from the image-plane center to each pixel by multiplying the distance by a distance gain in accordance with said G pixel;

a first distance balance gain correction step of multiplying the distance gain in which said G pixel is used as a reference by the distance balance gain of said R pixel; and

a second distance balance gain correction step of multiplying the distance gain in which said G pixel is used as a reference by the distance balance gain of said B pixel.

13. The recording medium having recorded thereon a computer-readable program according to claim 11, said program further comprising, when said image is composed of four colors of a Gr pixel, an R pixel, a B pixel, and a Gb pixel, or four colors of an E pixel, an R pixel, a B pixel, and a G pixel:

a second distance computation step of computing the distance from the image-plane center to each pixel by multiplying the distance by a distance gain in accordance with said Gb pixel or said G pixel;

a first balance gain correction step of multiplying the distance gain in which said Gb pixel or said G pixel is used as a reference by the distance balance gain of said R pixel;

a second balance gain correction step of multiplying the distance gain in which said Gb pixel or said G pixel is used as a reference by the distance balance gain of said B pixel; and

a third balance gain correction step of multiplying the distance gain in which said Gb pixel or said G pixel is used as a reference by the distance balance gain of said Gr pixel or said E pixel.

14. A program for allowing a computer to execute image processing of an image processing apparatus for correcting shading of a captured image, the program comprising:

a first distance computation step of computing the distance from the image-plane center to each pixel by multiplying the distance by a distance gain;

an obtaining step of obtaining a correction value for correcting the shading of said image on the basis of said distance computed in said first distance computation step; and

a correction step of correcting the signal of each of said pixels on the basis of said correction value obtained in said obtaining step.

15. The program according to claim 14, further comprising, when said image is composed of three colors of a G pixel, an R pixel, and a B pixel:

a second distance computation step of computing the distance from the image-plane center to each pixel by multiplying the distance by a distance gain in accordance with said G pixel;

a first distance balance gain correction step of multiplying the distance gain in which said G pixel is used as a reference by the distance balance gain of said R pixel; and

a second distance balance gain correction step of multiplying the distance gain in which said G pixel is used as a reference by the distance balance gain of said B pixel.

16. The program according to claim 14, further comprising, when said image is composed of four colors of a Gr pixel, an R pixel, a B pixel, and a Gb pixel, or four colors of an E pixel, an R pixel, a B pixel, and a G pixel:

a second distance computation step of computing the distance from the image-plane center to each pixel by multiplying the distance by a distance gain in accordance with said Gb pixel or said G pixel;

a first balance gain correction step of multiplying the distance gain in which said Gb pixel or said G pixel is used as a reference by the distance balance gain of said R pixel;

a second balance gain correction step of multiplying the distance gain in which said Gb pixel or said G pixel is used as a reference by the distance balance gain of said B pixel; and

a third balance gain correction step of multiplying the distance gain in which said Gb pixel or said G pixel is used as a reference by the distance balance gain of said Gr pixel or said E pixel.