Correction curve generating method, image processing method, image display unit, and storage medium

• US 20020122048A1
• Filed: 09/12/2001
• Published: 09/05/2002
• Est. Priority Date: 09/13/2000
• Status: Active Grant

• Current Assignee: Seiko Epson Corporation (Seiko Group)
• Original Assignee: Seiko Epson Corporation (Seiko Group)
• Inventors: Kanai, Masashi
• Granted Patent: US 6,940,522 B2
• Time in Patent Office: Days
• US Class Current: 345/690
• CPC Class Codes: H04N 5/58 in dependence upon ambient light
• CPC Class Codes: H04N 9/3182 Colour adjustment, e.g. white balance, shading or gamut white balance per se H04N9/73; control of amplitude of colour signals H04N9/68; colour control circuits for displays in general G09G5/02, G09G3/2003, G09G3/3607
• CPC Class Codes: H04N 9/3194 including sensor feedback
• CPC Class Codes: H04N 9/68 for controlling the amplitude of colour signals, e.g. automatic chroma control circuits H04N9/71, H04N9/73 take precedence; camera processing pipelines for controlling the colour saturation of colour signals H04N23/86

Abstract

It is intended to provided an image processing method, an image display unit, and a storage medium, capable of effecting an appropriate color reproduction even under a change in brightness of external illumination.

In an image display unit according to the present invention wherein a desired image processing is applied to inputted image data, an tone reproduction characteristic in a dark surround of the image display unit in a dark surround and an tone reproduction characteristic in a illuminated surround of the image display unit under illumination of a predetermined luminance value are measured by a measuring means and the tone reproduction characteristic in an illuminated surround is approximated to the tone reproduction characteristic in a dark surround in a desired input tone range by a characteristic approximating means. Further, on the basis of the approximated tone reproduction characteristic in an illuminated surround a correction curve is generated by a correction curve generating means and an image processing is performed for input image data on the basis of the generated correction curve.

Claims

1. A method for generating a correction curve for correcting image data inputted to an image display unit, comprising:

a measuring step of measuring an tone reproduction characteristic in a dark surround of said image display unit and an tone reproduction characteristic in an illuminated surround of the image display unit under illumination of a predetermined luminance value;

a characteristic approximating step of approximating said tone reproduction characteristic in an illuminated surround to said tone reproduction characteristic in a dark surround in a desired input tone range of input image data; and

a correction curve generating step of generating a correction curve on the basis of the approximated tone reproduction characteristic in an illuminated surround.

2. A method for performing an image processing for image data inputted to an image display unit, using a correction curve based on an tone reproduction characteristic in an illuminated surround of said image display unit under illumination of a predetermined luminance value, said tone reproduction characteristic in an illuminated surround having been approximated to an tone reproduction characteristic in a dark surround of the image display unit.

3. The method according to claim 2, having a plurality of correction curves obtained using different said predetermined luminance values.

4. The method according to claim 2, wherein said desired input tone range comprises a middle tone range and the vicinity thereof.

5. The method according to claim 2, wherein said tone reproduction characteristic in a dark surround and said tone reproduction characteristic in an illuminated surround are normalized to a predetermined luminance range, and in the desired input tone range of input image data the normalized tone reproduction characteristic in an illuminated surround is approximated to the normalized tone reproduction characteristic in a dark surround.

6. The method according to claim 2, wherein a correction curve is subjected to a rounding processing in a low or high tone region.

7. The method according to claim 6, wherein the degree of said rounding processing is adjustable.

8. The method according to claim 2, wherein the degree of approximation is adjustable.

9. The method according to claim 3, including a selection step of selecting one of plural correction curves on the basis of a luminance value of external illumination, and wherein the input image data is subjected to an image processing on the basis of the selected correction curve.

10. The method according to claim 9, further including a step of inputting the luminance value of external illumination used in said selection step.

11. The method according to claim 9, further including a step of measuring the luminance value of external illumination used in said selection step.

14. The image display unit according to claim 12, having a plurality of correction curves obtained using different said predetermined luminance values.

16. The image display unit according to claim 12, wherein said desired input tone range comprises a middle tone range and the vicinity thereof.

17. The image display unit according to claim 12, wherein said tone reproduction characteristic in a dark surround and said tone reproduction characteristic in an illuminated surround are normalized to a predetermined luminance range, and in the desired input tone range of input image data the normalized tone reproduction characteristic in an illuminated surround is approximated to the normalized tone reproduction characteristic in a dark surround.

18. The image display unit according to claim 12, wherein a correction curve is subjected to a rounding processing in a low or high tone region.

19. The image display unit according to claim 18, wherein the degree of said rounding processing is adjustable.

20. The image display unit according to claim 12, wherein the degree of approximation is adjustable.

21. The image display unit according to claim 14, including a selection means for selecting one of plural correction curves on the basis of a luminance value of external illumination, and wherein the input image data is subjected to an image processing on the basis of the selected correction curve.

22. The image display unit according to claim 21, further including a means for inputting the luminance value of external illumination used in said selection means.

23. The image display unit according to claim 21, further including a means for measuring the luminance value of external illumination used in said selection means.

25. The computer-readable medium according to claim 24, having a plurality of correction curves obtained using different said predetermined luminance values.

26. The computer-readable medium according to claim 24, wherein said desired input tone range comprises a middle tone range and the vicinity thereof.

27. The computer-readable medium according to claim 24, wherein said tone reproduction characteristic in a dark surround and said tone reproduction characteristic in an illuminated surround are normalized to a predetermined luminance range, and in the desired input tone range of input image data the normalized tone reproduction characteristic in an illuminated surround is approximated to the normalized tone reproduction characteristic in a dark surround.

28. The computer-readable medium according to claim 24, wherein a correction curve is subjected to a rounding processing in a low or high tone region.

29. The computer-readable medium according to claim 28, wherein the degree of said rounding processing is adjustable.

30. The computer-readable medium according to claim 24, wherein the degree of approximation is adjustable.

31. The computer-readable medium according to claim 25, including a selection processing of selecting one of plural correction curves on the basis of a luminance value of external illumination, and wherein the input image data is subjected to an image processing on the basis of the selected correction curve.

32. The computer-readable medium according to claim 31, further including a processing of inputting the luminance value of external illumination used in said selection processing.

33. The computer-readable medium according to claim 31, further including a processing of measuring the luminance value of external illumination used in said selection processing.

35. The computer-readable medium according to claim 34, having a plurality of correction curves obtained using different said predetermined luminance values.

36. The computer-readable medium according to claim 34, wherein said desired input tone range comprises a middle tone range and the vicinity thereof.

37. The computer-readable medium according to claim 34, wherein said tone reproduction characteristic in a dark surround and said tone reproduction characteristic in an illuminated surround are normalized to a predetermined luminance range, and in the desired input tone range of input image data the normalized tone reproduction characteristic in an illuminated surround is appropriated to the normalized tone reproduction characteristic in a dark surround.

38. The computer-readable medium according to claim 34, wherein a correction curve is subjected to a rounding processing in a low or high tone region.

39. The computer-readable medium according to claim 38, wherein the degree of said rounding processing is adjustable.

40. The computer-readable medium according to claim 34, wherein the degree of approximation is adjustable.

12. An image display unit for performing an image processing for an inputted image data, using a correction curve based on an tone reproduction characteristic in an illuminated surround of said image display unit under illumination of a predetermined luminance value, said tone reproduction characteristic in an illuminated surround having been approximated to an tone reproduction characteristic in a dark surround of the image display unit.

13. An image display unit for performing an image processing for an inputted image data, wherein the image display unit performs the image processing for the inputted data based on a correction curve, which is sequentially generated by sequentially repeating a method for generating the correction curve comprising:

a measuring step of measuring an tone reproduction characteristic in a dark surround of said image display unit and an tone reproduction characteristic in an illuminated surround of the image display unit under illumination of a predetermined luminance value;

a characteristic approximating step of approximating said tone reproduction characteristic in an illuminated surround to said tone reproduction characteristic in a dark surround in a desired input tone range of input image data; and

a correction curve generating step of generating a correction curve on the basis of the approximated tone reproduction characteristic in an illuminated surround.

15. An image display unit for performing an image processing for an inputted image data, comprising a storage means for storing a plurality of correction curves, which are generated by repeating a method for generating the correction curve, wherein a predetermined luminance value is changed each time, comprising:

a measuring step of measuring an tone reproduction characteristic in a dark surround of said image display unit and an tone reproduction characteristic in an illuminated surround of the image display unit under illumination of the predetermined luminance value;

a characteristic approximating step of approximating said tone reproduction characteristic in an illuminated surround to said tone reproduction characteristic in a dark surround in a desired input tone range of input image data; and

a correction curve generating step of generating a correction curve on the basis of the approximated tone reproduction characteristic in an illuminated surround.

24. A computer-readable medium having a program of instructions for execution by the computer to perform an image processing for image data inputted to an image display unit, using a correction curve based on an tone reproduction characteristic in an illuminated surround of said image display unit under illumination of a predetermined luminance value, said tone reproduction characteristic in an illuminated surround having been approximated to an tone reproduction characteristic in a dark surround of the image display unit.

34. A computer-readable medium storing a correction curve for performing an image processing for image data inputted to an image display unit, wherein the correction curve is based on an tone reproduction characteristic in an illuminated surround of said image display unit under illumination of a predetermined luminance value, said tone reproduction characteristic in an illuminated surround having been approximated to an tone reproduction characteristic in a dark surround of the image display unit.