Image pick-up apparatus and image processing method

1. An image pick-up apparatus comprising:

an image pick-up device that includes at least three kinds of color filters and photoelectric conversion elements formed under the color filters respectively;

a noise reduction processing portion that applies noise reduction processing to image pick-up signals output from the image pick-up device; and

a level difference correction portion that executes correction to reduce a level difference between first and second ones of the noise reduction-processed image pick-up signals obtained from the photoelectric conversion elements formed under two color filters which are of the same kind but different in arrangement pattern of color filters arranged around the two color filters,

wherein the level difference correction portion changes correction strength in accordance with strength of noise reduction processing executed by the noise reduction processing portion.

2. The image pick-up apparatus according to claim 1 , wherein the noise reduction processing portion sets the strength of noise reduction processing to be large as photograph sensitivity in the image pick-up apparatus becomes large, and

the level difference correction portion changes the correction strength in accordance with the photograph sensitivity.

3. The image pick-up apparatus according to claim 1 further comprising an amplification portion that amplifies analog image pick-up signals output from the image pick-up device with a predetermined gain and output the amplified signal to the noise reduction portion,

wherein the noise reduction processing portion sets the strength of noise reduction processing to be large as the predetermined gain becomes large, and

the level difference correction portion changes the correction strength in accordance with the predetermined gain.

4. The image pick-up apparatus according to claim 1 further comprising:

an amplification portion that amplifies analog image pick-up signals output from the image pick-up device with a predetermined gain and output the amplified signal to the noise reduction portion; and

a detection portion that detects a noise level of a black level signal included in the image pick-up signals, wherein the noise reduction processing portion sets the strength of noise reduction processing to be large as photograph sensitivity in the image pick-up apparatus or the predetermined gain becomes large,

wherein the noise level of the black level signal increases as the photograph sensitivity in the image pick-up apparatus or the predetermined gain increases, and

the level difference correction portion changes the correction strength in accordance with the noise level of the black level signal.

5. The image pick-up apparatus according to claim 1 further comprising a storage portion that stores parameters for determining the correction strength in accordance with the strength of the noise reduction processing,

wherein the level difference correction portion reads the parameters corresponding to the set strength of the noise reduction processing from the storage portion and executes correction in accordance with the parameters.

6. The image pick-up apparatus according to claim 1 further comprising a storage portion that stores a function using the strength of the noise reduction processing as a variable to calculate parameters for determining the correction strength,

wherein the level difference correction portion executes correction in accordance with the parameters calculated based on the set strength of the noise reduction processing and the function.

7. The image pick-up apparatus according to claim 2 further comprising a storage portion which stores parameters for determining the correction strength in accordance with the photograph sensitivity,

wherein the level difference correction portion reads the parameters corresponding to the set photograph sensitivity from the storage portion and executes correction in accordance with the parameters.

8. The image pick-up apparatus according to claim 2 further comprising a storage portion which stores a function using the set photograph sensitivity as a variable to calculate parameters for determining the correction strength,

wherein the level difference correction portion executes correction in accordance with the parameters calculated based on the set photograph sensitivity and the function.

9. The image pick-up apparatus according to claim 3 further comprising a storage portion which stores parameters for determining the correction strength in accordance with the predetermined gain,

wherein the level difference correction portion reads the parameters corresponding to the predetermined gain from the storage portion and executes correction in accordance with the parameters.

10. The image pick-up apparatus according to claim 3 further comprising a storage portion which stores a function using the predetermined gain as a variable to calculate parameters for determining the correction strength,

wherein the level difference correction portion executes correction in accordance with the parameters calculated based on the predetermined gain and the function.

11. The image pick-up apparatus according to claim 4 further comprising a storage portion which stores parameters for determining the correction strength in accordance with the noise level of the black level signal,

wherein the level difference correction portion reads the parameters corresponding to the noise level of the black level signal from the storage portion and executes correction in accordance with the parameters.

12. The image pick-up apparatus according to claim 4 , further comprising a storage portion which stores a function using the noise level of the black level signal as a variable to calculate parameters for determining the correction strength,

wherein the level difference correction portion executes correction in accordance with the parameters calculated based on the noise level of the black level signal and the function.

13. The image pick-up apparatus according to claim 1 , wherein the level difference correction portion changes the correction strength by changing a correction coefficient by which at least one of the first and second image pick-up signals is multiplied.

14. The image pick-up apparatus according to claim 13 , wherein the level difference correction portion sets the correction coefficient to be small as the strength of noise reduction processing becomes large.

15. The image pick-up apparatus according to claim 1 further comprising:

an AD conversion portion which converts analog image pick-up signals output from the image pick-up device into digital signals; and

an offset subtraction portion which subtracts an offset component at AD conversion executed by the AD conversion portion from the image pick-up signals after the noise reduction processing,

wherein the level difference correction portion applies correction for reducing the level difference to the image pick-up signals after subtraction of the offset component.

16. A signal processing method comprising:

applying noise reduction processing to image pick-up signals output from an image pick-up device including at least three kinds of color filters and photoelectric conversion elements formed under the color filters respectively; and

reducing a level difference between first and second ones of the noise reduction-processed image pick-up signals obtained from the photoelectric conversion elements formed under two color filters of the same kind but different in arrangement pattern of color filters arranged around the two color filters,

wherein correction strength in the reducing step is changed in accordance with strength of the noise reduction processing.

17. The signal processing method according to claim 16 , wherein the strength of the noise reduction processing is set to be large as photograph sensitivity in an image pick-up apparatus becomes large, and

the correction strength is changed in accordance with the photograph sensitivity in the reducing step.

18. The signal processing method according to claim 16 , further comprising:

amplifying analog image pick-up signals output from the image pick-up device with a predetermined gain,

wherein the strength of the noise reduction processing is set to be large as the predetermined gain becomes large, and

the correction strength is changed in accordance with the predetermined gain in the reducing step.

19. The signal processing method according to claim 16 , further comprising:

amplifying analog image pick-up signals output from the image pick-up device with a predetermined gain; and

detecting a noise level of a black level signal included in the image pick-up signals,

wherein the noise level of the black level signal increases as photograph sensitivity set in an image pick-up apparatus or the predetermined gain increases,

the strength of the noise reduction processing is set to be large as the set photograph sensitivity or the predetermined gain becomes large, and

the correction strength is changed in accordance with the noise level of the black level signal in the correction step.

20. The image processing method according to claim 16 , wherein the correction strength is changed by changing a correction coefficient by which at least one of the first and second image pick-up signals is multiplied in the correction step.

21. The signal processing method according to claim 20 , wherein the correction coefficient is set to be small as the strength of the noise reduction processing becomes large in the correction step.

22. The image processing method according to claim 16 further comprising:

converting analog image pick-up signals output from the image pick-up device into digital signals; and

subtracting an offset component at AD conversion executed by the converting step from the image pick-up signals after the noise reduction processing,

wherein correction for reducing the level difference to the image pick-up signals after subtraction of the offset component is executed in the correction step.