Image signal processing device, digital camera and computer program product for processing image signal

• US 20070165113A1
• Filed: 02/26/2007
• Published: 07/19/2007
• Est. Priority Date: 12/08/2000
• Status: Active Grant

• Current Assignee: Nikon Corporation
• Original Assignee: Nikon Corporation
• Inventors: Suzuki, Masahiro
• Granted Patent: US 7,750,948 B2
• Time in Patent Office: Days
• US Class Current: 348/223.100
• CPC Class Codes: H04N 23/88 for colour balance, e.g. white-balance circuits or colour temperature control

Abstract

R, G and B signals are output from individual pixels provided at an image-capturing element. Pixel output averages corresponding to the R, G and B signals are calculated for each of partition areas into which the light-receiving surface of the image-capturing element is divided. Ratios of the R and B pixel output averages to the G pixel output average are calculated for each partition area. Then, any area with the ratios of the pixel output averages within a predetermined range is extracted from the plurality of partition areas. R and B white balance gains are calculated based upon the total sums of the pixel output averages corresponding to the individual colors in the extracted area. A white balance adjustment is then executed by multiplying the values of R and B pixel outputs by the corresponding white balance gains.

Claims

1. An image signal processing device that processes an image signal constituting a subject image captured by an image-capturing element, comprising:

an average calculating unit that calculates pixel output averages for individual colors in each of a plurality of partition areas into which a light-receiving surface of the image-capturing element is divided based upon the image signal;

an average ratio calculating unit that calculates a ratio of a pixel output average corresponding to another color to a pixel output average of a reference color for each partition area;

an area extracting unit that extracts an area having a ratio of pixel output averages within a predetermined range; and

a white balance adjustment unit that performs a white balance adjustment based upon pixel outputs corresponding to the individual colors from the extracted area.

2. An image signal processing device according to claim 1, wherein:

the white balance adjustment unit includes;

a total sum calculating unit that calculates total sums of pixel output averages corresponding to the individual colors in the extracted area;

a gain calculating unit that calculates a white balance gain for a color other than the reference color based upon the total sums corresponding to the individual colors; and

a pixel output adjustment unit that performs white balance adjustment by multiplying pixel outputs corresponding to the color other than the reference color by the white balance gain.

3. An image signal processing device according to claim 1, wherein:

the pixel outputs include a red-color component, a green-color component and a blue color component and the reference color is green.

4. An image signal processing device according to claim 2, wherein:

the pixel outputs include a red-color component, a green-color component and a blue color component and the reference color is green.

5. An image signal processing device according to claim 1, wherein:

the pixel outputs include a green-color component, a yellow-color component, a cyan-color component and a magenta-color component and the reference color is green.

6. An image signal processing device according to claim 2, wherein:

the pixel outputs include a green-color component, a yellow-color component, a cyan-color component and a magenta-color component and the reference color is green.

7. A digital camera having:

an image signal processing device according to claim 1;

and

a recording image-capturing element that outputs an image signal used for recording the captured subject image into a recording medium, wherein;

an image signal to be used for white balance adjustment is the image signal output by the recording image-capturing element.

8. A digital camera having:

an image signal processing device according to claim 1;

a recording image-capturing element that outputs an image signal for recording the captured subject image into a recording medium; and

a photometering image-capturing element that outputs a photometering signal indicating a subject brightness level in each of photometering areas into which a photographic field is divided, wherein;

an image signal to be used for white balance adjustment is the image signal output by the photometering image-capturing element.

9. A computer-readable computer program product having a program to be used to process an image signal constituting a subject image captured at an image-capturing element, with the program comprising:

average calculation processing in which pixel output averages are calculated for individual colors in each of a plurality of partition areas into which a light-receiving surface of the image-capturing element is divided based upon the image signal;

average ratio calculation processing in which a ratio of the pixel output average corresponding to another color to the pixel output average corresponding to a reference color is calculated for each partition area;

area extraction processing in which any area having a ratio of pixel output averages within a predetermined range is extracted from the plurality of partition areas; and

white balance adjustment processing in which white balance adjustment is performed based upon pixel outputs corresponding to the individual colors from the extracted area.

10. A computer program product according to claim 9, with the program further comprising:

total sum calculation processing in which total sums of the pixel output averages corresponding to the individual colors in the extracted area are calculated;

gain calculation processing in which a white balance gain for a color other than the reference color is calculated based upon the total sums corresponding to the individual colors; and

pixel output adjustment processing in which a white balance adjustment is performed by multiplying pixel outputs corresponding to the color other than the reference color by the white balance gain.

11. A computer program product according to claim 9, constituted as a recording medium having recorded therein the program.

12. A computer program product according to claim 9, constituted as a carrier wave having the program embodied as a data signal thereupon.

13. An image signal processing device according to claim 9, wherein:

the pixel outputs include a red-color component, a green-color component and a blue color component and the reference color is green.

14. A computer program product according to claim 10, wherein:

the pixel outputs include a red-color component, a green-color component and a blue color component and the reference color is green.

15. A computer program product according to claim 9, wherein:

the pixel outputs include a green-color component, a yellow-color component, a cyan-color component and a magenta-color component and the reference color is green.

16. A computer program product according to claim 10, wherein:

the pixel outputs include a green-color component, a yellow-color component, a cyan-color component and a magenta-color component and the reference color is green.

17. A computer program product according to claim 9, wherein:

an image signal to be utilized in white balance adjustment is an image signal used for recording the captured subject image into a recording medium.

18. A computer program product according to claim 10, wherein:

an image signal to be utilized in white balance adjustment is a photometering signal indicating subject brightness levels each corresponding to one of a plurality of photometering areas into which a photographic field is divided.

19. An image signal processing device that processes an image signal constituting a subject image captured by an image-capturing element comprising:

a saturation calculating unit that calculates a saturation level in each of a plurality of partition areas based upon pixel outputs from the partition areas into which a light-receiving surface of the image-capturing element is divided;

an area extracting unit that extracts any area having a saturation level within a predetermined range from the plurality of partition areas; and

a white balance adjustment unit that performs a white balance adjustment based upon pixel outputs corresponding to individual colors from the extracted area.

20. A digital camera having:

an image signal processing device according to claim 19; and

a recording image-capturing element that outputs an image signal used for recording the captured subject image into a recording medium, wherein;

an image signal to be used for white balance adjustment is the image signal output by the recording image-capturing element.

21. A digital camera having:

an image signal processing device according to claim 19;

a recording image-capturing element that outputs an image signal for recording the captured subject image into a recording medium; and

a photometering image-capturing element that outputs a photometering signal indicating a subject brightness level in each of photometering areas into which a photographic field is divided, wherein;

an image signal to be used for white balance adjustment is the image signal output by the photometering image-capturing element.

22. A computer-readable computer program product having a program to be used to process an image signal constituting a subject image captured at an image-capturing element, with the program comprising:

saturation calculation processing in which a saturation level in each of a plurality of partition areas is calculated based upon pixel outputs from the partition areas into which a light-receiving surface of the image-capturing element is divided;

area extraction processing in which any area having a saturation level within a predetermined range is extracted from the plurality of partition areas; and

white balance adjustment processing in which white balance adjustment is performed based upon pixel outputs corresponding to individual colors from the extracted area.