White balance control method, imaging apparatus and storage medium storing white balance control program

• US 7,969,483 B2
• Filed: 05/07/2007
• Issued: 06/28/2011
• Est. Priority Date: 05/11/2006
• Status: Expired due to Fees

• Current Assignee: Olympus Corporation
• Original Assignee: Olympus Imaging Corporation (Olympus Corporation)
• Inventors: Takasumi, Shinya
• Primary Examiner(s): Chan; Jason
• Assistant Examiner(s): OSINSKI, MICHAEL S
• Application Number:
  US11/800,573
• Publication Number:
  US 20070268380A1
• Time in Patent Office: 1,513 Days
• Field of Search: 3482221-2251, 348/229.1, 3482311-2313
• US Class Current: 348/224.1
• CPC Class Codes: H04N 1/6077 Colour balance, e.g. colour cast correction
• CPC Class Codes: H04N 1/608 within the L, C1, C2 colour signals
• CPC Class Codes: H04N 1/6086 by scene illuminant, i.e. conditions at the time of picture capture, e.g. flash, optical filter used, evening, cloud, daylight, artificial lighting, white point measurement, colour temperature
• CPC Class Codes: H04N 23/663 for controlling interchangeable camera parts based on electronic image sensor signals
• CPC Class Codes: H04N 23/88 for colour balance, e.g. white-balance circuits or colour temperature control
• CPC Class Codes: H04N 5/772 the recording apparatus and the television camera being placed in the same enclosure

Abstract

There is provided a white balance control method. A color space coordinate expressing a color signal of each divided block is transformed into a white balance determination space coordinate. A light source estimation area and a high-saturation determination area are set in a white balance determination space to which the transformed white balance determination space coordinate belongs. A kind of the light source is estimated based on a white balance determination space coordinate distribution in the light source estimation area. A kind of the light source is determined based on the estimated kind of the light source and a white balance determination space coordinate distribution in the high-saturation determination area. White balance control information is calculated based on the determined kind of the light source. White balance control with respect to an image signal is carried out based on the calculated white balance control information.

Claims

1. A white balance control method of carrying out white balance control using a color signal of each of several blocks obtained by dividing an image signal equivalent to one frame in a screen, comprising:

transforming a color space coordinate expressing the color signal of each divided block into a white balance determination space coordinate for determining a white balance in the screen;

setting a light source estimation area for estimating a kind of a light source in the white balance control and a high-saturation determination area for determining whether or not the color signal of each block in the screen has high saturation, in a white balance determination space to which the transformed white balance determination space coordinate belongs;

estimating the kind of the light source based on a white balance determination space coordinate distribution in the light source estimation area;

determining a kind of the light source based on the estimated kind of the light source and a white balance determination space coordinate distribution in the high-saturation determination area;

calculating a white balance control information based on the determined kind of the light source;

carrying out white balance control with respect to the image signal based on the calculated white balance control information;

determining whether or not an imaging apparatus including an imaging unit capturing the image signal is a lens detachable type;

reading characteristic information of the imaging unit, characteristic information of a lens and characteristic information of each specific light source, which are previously stored, when it is determined that the imaging apparatus is a lens detachable type;

calculating white balance control information of each specific light source based on the read characteristic information; and

transforming the calculated white balance control information of each specific light source into the white balance determination space coordinate,

wherein the light source estimation area and the high-saturation determination area are set to have an area overlapping each other, and the kind of the light source is determined based on the white balance determination space coordinate distribution in the light source estimation area, the white balance determination space coordinate distribution in the high-saturation determination area and a white balance determination space coordinate distribution in the area overlapping the light source estimation area with the high-saturation determination area, and

wherein one or more light source estimation areas are set corresponding to a specific light source, while one or more high-saturation determination areas are set corresponding to hue, and each set light source estimation area has an area mutually overlapping with one or more high-saturation determination areas.

2. A white balance control method of carrying out white balance control using a color signal of each of several blocks obtained by dividing an image signal equivalent to one frame in a screen, comprising:

transforming a color space coordinate expressing the color signal of each divided block into a white balance determination space coordinate for determining a white balance in the screen;

setting a light source estimation area for estimating a kind of a light source in the white balance control and a high-saturation determination area for determining whether or not the color signal of each block in the screen has high saturation, in a white balance determination space to which the transformed white balance determination space coordinate belongs;

estimating the kind of the light source based on a white balance determination space coordinate distribution in the light source estimation area;

determining a kind of the light source based on the estimated kind of the light source and a white balance determination space coordinate distribution in the high-saturation determination area;

calculating a white balance control information based on the determined kind of the light source;

carrying out white balance control with respect to the image signal based on the calculated white balance control information;

determining whether or not an imaging apparatus including an imaging unit capturing the image signal is a lens detachable type;

reading white balance control information set for each specific light source previously stored when it is determined that the imaging apparatus is not a lens detachable type; and

transforming the read white balance control information corresponding to each specific light source into the white balance determination space coordinate,

wherein the light source estimation area and the high-saturation determination area are set to have an area overlapping each other, and the kind of the light source is determined based on the white balance determination space coordinate distribution in the light source estimation area, the white balance determination space coordinate distribution in the high-saturation determination area and a white balance determination space coordinate distribution in the area overlapping the light source estimation area with the high-saturation determination area, and

wherein one or more light source estimation areas are set corresponding to a specific light source, while one or more high-saturation determination areas are set corresponding to hue, and each set light source estimation area has an area mutually overlapping with one or more high-saturation determination areas.

3. An imaging apparatus comprising:

an imaging unit which images an object to capture an imaging signal equivalent to one frame;

a dividing unit which divides the imaging signal into several blocks in a screen;

a coordinate transformation unit which transforms a color space coordinate expressing a color signal of the divided each block into a white balance determination space coordinate for determining a white balance in the screen;

a storage unit which stores a white balance control information set for each specific light source;

a determination unit which determines whether the imaging apparatus is a lens detachable type;

a reading unit which reads the stored white balance control information when it is determined that the imaging apparatus is not a lens detachable type;

a setting unit which sets a light source estimation area for estimating a kind of light source in the white balance control and a high-saturation determination area for determining whether or not a color signal of each block in the screen has high saturation, in a white balance determination space based on the read white balance control information and the transformed white balance determination space coordinate;

a light source estimation unit which estimates the kind of the light source based on a white balance determination space coordinate distribution in the light source estimation area;

a light source determination unit which determines a kind of the light source based on the estimated kind of the light source and a white balance determination space coordinate distribution in the high-saturation determination area;

a white balance control information calculation unit which calculates a white balance control information based on the determined kind of the light source; and

a white balance control unit which carries out white balance control with respect to the image signal based on the calculated white balance control information.

4. An imaging apparatus comprising:

an imaging unit which images an object to capture an imaging signal equivalent to one frame;

a dividing unit which divides the imaging signal into several blocks in a screen;

a coordinate transformation unit which transforms a color space coordinate expressing a color signal of the divided each block into a white balance determination space coordinate for determining a white balance in the screen;

a first storage unit which stores a characteristic information of the imaging unit;

a photographing lens freely detachable with respect to the imaging apparatus, the photographing lens having a second storage unit which stores a characteristic information of the photographing lens;

a third storage unit which stores a characteristic information for each specific light source;

a determination unit which determines whether the imaging apparatus is a lens detachable type;

a reading unit which reads the characteristic information of the imaging unit, characteristic information of the photographing lens and characteristic information for each specific light source when it is determined that the imaging apparatus is a lens detachable type;

a calculation unit which calculates a white balance control information corresponding to each specific light source based on the read characteristic information of the imaging unit, characteristic information of the photographing lens and characteristic information of each specific light source;

a setting unit which sets a light source estimation area for estimating a kind of light source in the white balance control and a high-saturation determination area for determining whether or not a color signal of each block in the screen has high saturation, in a white balance determination space based on the calculated white balance control information and the transformed white balance determination space coordinate;

a light source estimation unit which estimates a kind of the light source based on a white balance determination space coordinate distribution in the light source estimation area;

a light source determination unit which determines a kind of the light source based on the estimated kind of the light source and a white balance determination space coordinate distribution in the high-saturation determination area;

a white balance control information calculating unit which calculates a white balance control information based on the determined kind of the light source; and

a white balance control unit which carries out white balance control with respect to the image signal based on the calculated white balance control information.

5. The device according to claim 4, wherein the characteristic information of the imaging unit includes a spectral sensitivity characteristic of the imaging unit, and the characteristic information of the photographing lens includes a spectral transmittance characteristic of the photographing lens, and further, the characteristic information of each specific light source includes a spectral radiation luminance characteristic of each specific light source.