Imaging apparatus and imaging method

• US 8,081,242 B2
• Filed: 08/17/2009
• Issued: 12/20/2011
• Est. Priority Date: 08/20/2008
• Status: Expired due to Fees

• Current Assignee: Ricoh Company Limited
• Original Assignee: Ricoh Company Limited
• Inventors: Shiraishi, Kenji
• Primary Examiner(s): HO, TUAN V
• Application Number:
  US12/542,023
• Publication Number:
  US 20100045814A1
• Time in Patent Office: 855 Days
• Field of Search: 348/222.1, 348/223.1, 348/256, 348272-273, 348/234
• US Class Current: 348/256
• CPC Class Codes: H04N 23/631 Graphical user interfaces [GUI] specially adapted for controlling image capture or setting capture parameters
• CPC Class Codes: H04N 23/673 based on contrast or high frequency components of image signals, e.g. hill climbing method
• CPC Class Codes: H04N 23/675 comprising setting of focusing regions
• CPC Class Codes: H04N 23/70 Circuitry for compensating brightness variation in the scene
• CPC Class Codes: H04N 23/741 by increasing the dynamic range of the image compared to the dynamic range of the electronic image sensors
• CPC Class Codes: H04N 23/843 Demosaicing, e.g. interpolating colour pixel values
• CPC Class Codes: H04N 25/134 based on three different wavelength filter elements

Abstract

An imaging apparatus, includes: an image sensor having a light receiving surface with a plurality of pixels and a plurality-of-color separation filter, which receives light from a photographic subject which is incident via an optical system on the surface via the filter, outputs a pixel output of each pixel, and images an image of the subject; a pixel output judging section which judges if each pixel output reaches each predetermined saturation level or not; a pixel output compensation processor which compensates a pixel output of a specific color filter based on a pixel output of another color separation filter in the vicinity which is less than its predetermined saturation level; and a bit compression convertor.

Claims

1. An imaging apparatus, comprising:

an image sensor having a light receiving surface with a plurality of pixels and a color separation filter of a plurality of colors placed on a front side of the pixels, which receives light from a photographic subject which is incident via an optical system on the light receiving surface via the color separation filter, outputs a pixel output of each pixel, and images an image of the photographic subject;

a pixel output judging section which judges if each pixel output reaches each predetermined saturation level or not;

a pixel output compensation processor which performs a compensating process that calculates a pixel output of a pixel where a color separation filter of a specific color is placed, and expands a dynamic range of the image which the image sensor images, based on a pixel output of a pixel where another color separation filter is placed in a vicinity of the pixel where the color separation filter of the specific color is placed and the pixel output of the pixel where the another color separation filter is placed is less than its predetermined saturation level; and

a bit compression convertor which has a bit compression conversion characteristic in which a data compression rate of a pixel output for brightness where the pixel output of the pixel where the color separation filter of the specific color is placed is less than its predetermined saturation level is smaller than a data compression rate of the pixel output for brightness where the pixel output of the pixel where the color separation filter of the specific color is placed reaches its predetermined saturation level, and converts data of the pixel output converted to a second bit number which is larger than a first bit number from the first bit number to the first bit number again based on the bit compression conversion characteristic.

2. The imaging apparatus according to claim 1, wherein the compensating process is performed in a case where the pixel output judging section judges that the pixel output of the pixel where the color separation filter of the specific color is placed reaches its predetermined saturation level.

3. The imaging apparatus according to claim 1, wherein in a case where the pixel output of the pixel where the another color separation filter is placed in the vicinity of the pixel where the color separation filter of the specific color is placed exceeds a predetermined output level, the pixel output compensation processor performs the compensating process.

4. The imaging apparatus according to claim 1, wherein in a case where the pixel output judging section judges the pixel output, a processing unit is an area comprising 2×

2 pixels in horizontal and vertical directions.

5. The imaging apparatus according to claim 1, wherein in a case where there are a plurality of pixels where same color filters are placed in a predetermined range, a value of the pixel output where the same color filters are placed is an average value of the pixels where the same color filters are placed.

6. The imaging apparatus according to claim 1, wherein on an optical axis of the optical system, a color filter of a same color as the color separation filter of the specific color which is movable is provided, so that a sensitivity of the another color separation filter is relatively lowered compared to a sensitivity of the color separation filter of the specific color.

7. The imaging apparatus according to claim 6, wherein plural pieces of the color filter are provided and each color filter has a different light transmission rate.

8. The imaging apparatus according to claim 1, further comprising:

an operation selector which is configured to select and execute the compensating process.

9. The imaging apparatus according to claim 1, wherein the bit compression conversion characteristic has a compression rate such that data of the pixel output before converting is an approximately same value as data of the pixel output after converting, in a case of brightness such that the pixel output of the pixel where the color filter of the specific color is placed becomes less than its predetermined saturation level and is low.

10. The imaging apparatus according to claim 1, wherein in a case where the pixel output of the color separation filter of the specific color after the compensating process is larger than the pixel output before the compensating process, the pixel output compensation processor uses the pixel output after the compensating process as the pixel output of the color separation filter of the specific color.

11. An imaging method, comprising:

a step of preparing an imaging apparatus, including;

an image sensor having a light receiving surface with a plurality of pixels and a color separation filter of a plurality of colors placed on a front side of the pixels, which receives light from a photographic subject which is incident via an optical system on the light receiving surface via the color separation filter, outputs a pixel output of each pixel, and images an image of the photographic subject;

a step of a pixel output judgment which judges if each pixel output reaches each predetermined saturation level or not;

a step of a pixel output compensation process which performs a compensating process that calculates a pixel output of a pixel where a color separation filter of a specific color is placed, and expands a dynamic range of the image which the image sensor images, based on a pixel output of a pixel where another color separation filter is placed in a vicinity of the pixel where the color separation filter of the specific color is placed and the pixel output of the pixel where the another color separation filter is placed is less than its predetermined saturation level; and

a step of a bit compression conversion which has a bit compression conversion characteristic in which a data compression rate of a pixel output for brightness where the pixel output of the pixel where the color separation filter of the specific color is placed is less than its predetermined saturation level is smaller than a data compression rate of the pixel output for brightness where the pixel output of the pixel where the color separation filter of the specific color is placed reaches its predetermined saturation level, and converts data of the pixel output converted to a second bit number which is larger than a first bit number from the first bit number to the first bit number again based on the bit compression conversion characteristic.

12. The imaging method according to claim 11, wherein the compensating process is performed in a case where the step of the pixel output judgment judges that the pixel output of the pixel where the color separation filter of the specific color is placed reaches its predetermined saturation level.

13. The imaging method according to claim 11, wherein in a case where the pixel output of the pixel where the another color separation filter is placed in the vicinity of the pixel where the color separation filter of the specific color is placed exceeds a predetermined output level, the step of the pixel output compensation process performs the compensating process.

14. The imaging method according to claim 11, wherein in a case where the step of the pixel output judgment judges the pixel output, a processing unit is an area comprising 2×

2 pixels in horizontal and vertical directions.

15. The imaging method according to claim 11, wherein in a case where there are a plurality of pixels where same color filters are placed in a predetermined range, a value of the pixel output where the same color filters are placed is an average value of the pixels where the same color filters are placed.

16. The imaging method according to claim 11, wherein on an optical axis of the optical system, a color filter of a same color as the color separation filter of the specific color which is movable is provided, so that a sensitivity of the another color separation filter is relatively lowered compared to a sensitivity of the color separation filter of the specific color.

17. The imaging method according to claim 16, wherein plural pieces of the color filter are provided and each color filter has a different light transmission rate.

18. The imaging method according to claim 11, further comprising:

a step of preparing an operation selector which is configured to select and execute the compensating process.

19. The imaging method according to claim 11, wherein the bit compression conversion characteristic has a compression rate such that data of the pixel output before converting is an approximately same value as data of the pixel output after converting, in a case of brightness such that the pixel output of the pixel where the color filter of the specific color is placed becomes less than its predetermined saturation level and is low.

20. The imaging method according to claim 11, wherein in a case where the pixel output of the color separation filter of the specific color after the compensating process is larger than the pixel output before the compensating process, the step of the pixel output compensation process uses the pixel output after the compensating process as the pixel output of the color separation filter of the specific color.