White balance adjustment method, image processing apparatus and electronic camera

• US 20030001958A1
• Filed: 02/04/2002
• Published: 01/02/2003
• Est. Priority Date: 05/24/2001
• Status: Active Grant

• Current Assignee: Nikon Corporation
• Original Assignee: Nikon Corporation
• Inventors: Hoshuyama, Hideo
• Granted Patent: US 7,184,079 B2
• Time in Patent Office: Days
• US Class Current: 348/223.1
• CPC Class Codes: H04N 23/84 for processing colour signals
• CPC Class Codes: H04N 23/88 for colour balance, e.g. white-balance circuits or colour temperature control

Abstract

An image-capturing device captures a subject image through an exchangeable lens. A white balance sensor that is set at a position conjugate with the position of the image-capturing device relative to the exchangeable lens to receive the light from the subject image and outputs color signals. A white balance adjustment signal calculation circuit calculates white balance adjustment basic signals based upon the color signals output from the white balance sensor and weighting points in conformance to the photographic range, the number of sets of red color data and the subject brightness value. Adjustment signals to be used for white balance adjustment are determined based upon the weighting points and the adjustment basic signals.

Claims

1. A white balance adjustment method comprising:

detecting chromaticity of a subject by using an image-capturing signal of an image of the subject that has been photographed,

analyzing a scene by using the image-capturing signal,

calculating a white balance adjustment gain for the image-capturing signal based upon the detected chromaticity of the subject and the results of analyzing the scene, and performing a white balance adjustment by applying the white balance adjustment gain to the image-capturing signal.

2. An image processing apparatus comprising:

a chromaticity detection unit that detects chromaticity of a subject by using an image-capturing signal of an image of the subject that has been photographed;

a scene analysis unit that analyzes a scene by using the image-capturing signal,

a gain calculation unit that calculates a white balance adjustment gain for the image-capturing signal based upon detected chromaticity of the subject and the results of analyzing the scene, and

a white balance adjustment unit that performs a white balance adjustment by applying the white balance adjustment gains to the image-capturing signal.

3. An electronic camera comprising:

an image-capturing device that captures a subject image passing through a photographic lens and outputs an image-capturing signal; and

an image processing apparatus in claim 2.

4. An electronic camera comprising:

an image-capturing device that captures a subject image passing through a photographic lens and outputs an image-capturing signal;

a chromaticity detection unit that detects chromaticity of the subject by using the image-capturing signal;

a gain calculation unit that calculates first and second gains by using different algorithms based upon the chromaticity detected by the chromaticity detection unit;

a scene analysis unit that analyzes a scene to be photographed,

a weighting value calculation unit that calculates first and second weighting values each for the first and second gains based on results of analyzing the scene;

a final gain calculation unit that calculates a white balance adjustment gain for the image-capturing signal based upon the first and second gains to which the first and second weighting values have been applied respectively; and

a white balance adjustment unit that performs a white balance adjustment by applying the white balance adjustment gains to the image-capturing signal.

5. An electronic camera according to claim 4, wherein:

the weighting value calculation unit calculates the weighting values so as to give dominance to either the first gain or the second gain.

6. An electronic camera according to claim 5, wherein:

the weighting value calculation unit weights the first gain and the second gain by providing different coefficients for the first gain and the second gain, with a positive coefficient set for one of the gains that is to be given dominance and a negative coefficient with a larger absolute value than the positive coefficient provided for the other gain.

7. An electronic camera according to claim 4, wherein:

the weighting value calculation unit includes a table of a relationship between results of analyzing the scene being photographed and the weighting values.

8. An electronic camera according to claim 4,wherein;

the gain calculation unit calculates a first gain by using a white balance adjustment signal calculating method achieved by averaging color signals over an entire image plane, a second gain by using a white balance adjustment signal calculating method achieved through multiple division white detection, and a third gain by using a white balance adjustment signal calculating method achieved through multiple division skin color detection,

the weighting value calculation unit analyzes a scene to be photographed by using a photographic range analysis method, a red color area analysis method and a brightness value analysis method, respectively and calculates a first weighting value for a first gain, a second weighting value for a second gain and a third weighting value for a third gain for each analysis methods for the individual results of analyzing the scene, and

the final gain calculation unit calculates the white balance gain to the image-capturing signals based upon the first gain to which the first weighting value has applied, the second gain to which the second weighting value has applied and the third gain to which the third weighting value has applied.

9. A computer-readable computer program product containing a control program for white balance adjustment, the control program comprising:

instruction for detecting chromaticity of a subject by using an image-capturing signal of an image of the subject that has been photographed,

instruction for analyzing the scene by using the image-capturing signal,

instruction for calculating a white balance adjustment gain for the image-capturing signal based upon the chromaticity of the subject and the results of analyzing the scene, and

instruction for performing a white balance adjustment by applying the white balance adjustment gain to the image-capturing signal.

10. A computer-readable computer program product according to claim 9, wherein;

the program product comprises a recording medium.

11. A computer-readable computer program product according to claim 9, wherein;

the program product comprises a carrier wave in which the control program is embodied.