Method and apparatus for varying focus in a scene

• US 6,741,251 B2
• Filed: 08/16/2001
• Issued: 05/25/2004
• Est. Priority Date: 08/16/2001
• Status: Expired due to Fees

• Current Assignee: Hewlett-Packard Development Company, L.P. (HP Inc.)
• Original Assignee: Hewlett-Packard Development Company, L.P. (HP Inc.)
• Inventors: Malzbender, Thomas
• Primary Examiner(s): Jankus, Almis R.
• Application Number:
  US09/932,691
• Publication Number:
  US 20030034977A1
• Time in Patent Office: 1,013 Days
• Field of Search: 345/426, 345/428, 345/582, 345/589, 382/254, 382/255, 382/302, 250/234
• US Class Current: 345/428
• CPC Class Codes: G06T 5/50 using two or more images, e.g. averaging or subtraction

Abstract

A method of varying focus in a scene. Specifically, one embodiment of the present invention discloses a method for modeling a scene using a parametric texture map (PTM) under varying focus conditions of one or more dimensions: e.g., focus depth and depth of field. A dataset of photographs is obtained under separate focus conditions. Approximation of the dataset creates an associated PTM representation that is capable of generating scenes of the photographic scene under varying focus conditions anywhere within the range of focus conditions specified by the initial data set. In addition, extrapolation yields results outside the range of focus conditions.

Claims

1. A method of varying focus in a scene, comprising:

a) obtaining a dataset of photographs of said scene, each of said dataset of photographs created under separate focus conditions within a range of focus conditions;

b) performing an approximation using said dataset of photographs that is capable of representing a spectrum of photographs of said scene, each of said spectrum of photographs having focus conditions within said range of focus conditions; and

c) recording a plurality of values associated with said approximation, said plurality of values capable of generating each of said spectrum of photographs.

2. The method as described in claim 1, further comprising:

obtaining three photographs for said dataset of photographs.

3. The method as described in claim 1, further comprising:

obtaining said dataset of photographs, each of said dataset of photographs created under separate focus conditions that vary in focus depth.

4. The method as described in claim 1, further comprising:

obtaining said dataset of photographs, each of said dataset of photographs created under separate focus conditions that vary in depth of field.

5. The method as described in claim 1, further comprising:

having said dataset of photographs define said range of focus conditions, said dataset of photographs having a first photograph with a minimum focus condition of −

1.0 and a second photograph with a maximum focus condition of +1.0.

6. The method as described in Claim 1, further comprising:

for each subpixel in said scene, obtaining a dataset of color values from said dataset of photographs;

for each subpixel in said scene, performing said approximation to determine a corresponding spectrum of color values from said spectrum of photographs by a corresponding quadratic polynomial function;

for each subpixel in said scene, recording a corresponding plurality of coefficients associated with said corresponding quadratic polynomial function.

7. The method as described in claim 6, further comprising:

for each subpixel in said scene, least mean squares curve fitting a dataset of color values from said dataset of photographs to determine said corresponding plurality of coefficients.

8. The method as described in claim 6, further comprising for each subpixel in said scene, recording said corresponding plurality of coefficients associated with said quadratic polynomial function, comprising:

Color Value(F, Focus Condition) =a₀F²+a₃F +a₅.

9. The method as described in claim 1, further comprising:

extrapolating from said dataset of photographs a plurality of photographs having focus conditions outside said range of focus conditions.

10. The method as described in claim 1, further comprising:

selecting a selected focus condition within said range of focus conditions;

synthesizing a selected photograph for said selected focus condition from said plurality of values; and

displaying said selected photograph.

15. The method as described in claim 1, further comprising:

for each subpixel, obtaining a dataset of color values from said dataset of photographs;

for each subpixel, interpolating a corresponding spectrum of color values from said spectrum of photographs by a corresponding biquadratic polynomial function that represents color values;

for each subpixel, recording a corresponding plurality of coefficients associated with said corresponding biquadratic polynomial function.

16. The method as described in claim 15, further comprising:

for each subpixel, least mean squares curve fitting a dataset of color values from said dataset of photographs to determine said corresponding plurality of coefficients.

17. The method as described in claim 15, further comprising for each subpixel, recording said corresponding plurality of coefficients associated with said quadratic polynomial function, comprising:

Color Value (F, Focus Depth;

D, Depth of Field)=a₀F²+a₁D²+a₂FD+a₃F+a₄D+a₅.

11. A method of varying focus in a scene, comprising:

a) obtaining a dataset of photographs of said scene, each of said dataset of photographs created under separate focus conditions within a region of focus conditions varying in two dimensions;

b) interpolating from said dataset of photographs a spectrum of photographs of said scene, each of said spectrum of photographs having focus conditions within said region of focus conditions;

c) recording a plurality of values associated with said interpolating for deriving each of said spectrum of photographs.

12. The method as described in claim 11, further comprising:

obtaining six photographs for said dataset of photographs.

13. The method as described in claim 11 further comprising:

obtaining said dataset of photographs within said region of focus conditions varying in focus depth and depth of field.

14. The method as described in claim 11, further comprising:

having said dataset of photographs define said region of focus conditions, a first photograph of said dataset of photographs having a minimum focus depth of −

1.0 and a second photograph of said dataset of photographs having a maximum focus depth of +1.0, and a third photograph of said dataset of photographs having a minimum depth of field of −

1.0 and a fourth photograph of said dataset of photographs having a maximum depth of field of +1.0.

18. The method as described in Claim 11, further comprising:

extrapolating from said dataset of photographs a plurality of photographs having focus conditions outside said region of focus conditions.

19. The method as described in claim 11, further comprising:

selecting a selected focus condition within said region of focus conditions;

synthesizing a selected photograph for said selected focus condition from said plurality of values; and

displaying said selected photograph.

20. A computer-readable medium containing computer-readable instructions for causing a computer to perform focus varying operations, comprising:

a) obtaining a dataset of photographs of said scene, each of said dataset of photographs created under separate focus conditions within a range of focus conditions;

b) performing an approximation using said dataset of photographs that is capable of representing a spectrum of photographs of said scene, each of said spectrum of photographs having focus conditions within said range of focus conditions; and

c) recording a plurality of values associated with said approximation, said plurality of values capable of generating each of said spectrum of photographs.

21. The computer-readable medium as described in claim 20, wherein said method further comprises:

obtaining three photographs for said dataset of photographs.

22. The computer-readable medium as described in claim 20, wherein said method further comprises:

obtaining said dataset of photographs, each of said dataset of photographs created under separate focus conditions that vary in focus depth.

23. The computer-readable medium as described in claim 20, wherein said method further comprises:

obtaining said dataset of photographs, each of said dataset of photographs created under separate focus conditions that vary in depth of field.

24. The computer-readable medium as described in claim 20, wherein said method further comprises:

having said dataset of photographs define said range of focus conditions, said dataset of photographs having a first photograph with a minimum focus condition of −

1.0 and a second photograph with a maximum focus condition of +1.0.

25. The computer-readable medium as described in claim 20, wherein said method further comprises:

for each subpixel in said scene, obtaining a dataset of color values from said dataset of photographs;

for each subpixel in said scene, performing said approximation to determine a corresponding spectrum of color values from said spectrum of photographs by a corresponding quadratic polynomial function;

for each subpixel in said scene, recording a corresponding plurality of coefficients associated with said corresponding quadratic polynomial function.

26. The computer-readable medium as described in claim 25, wherein said method further comprises:

for each subpixel in said scene, least mean squares curve fitting a dataset of color values from said dataset of photographs to determine said corresponding plurality of coefficients.

27. The computer-readable medium as described in claim 25, wherein said method further comprises for each subpixel in said scene, recording said corresponding plurality of coefficients associated with said quadratic polynomial function, comprising:

Color Value(F, Focus Condition) a₀F²+a₃F+a₅.

28. The computer readable medium as described in claim 20, wherein said method further comprises:

extrapolating from said dataset of photographs a plurality of photographs having focus conditions outside said range of focus conditions.

29. The computer readable medium as described in claim 20, wherein said method further comprises:

selecting a selected focus condition within said range of focus conditions;

synthesizing a selected photograph for said selected focus condition from said plurality of values; and

displaying said selected photograph.

30. A computer-readable medium having focus varying parameters stored thereon, said focus varying parameters comprising:

approximation data derived from a dataset of photographs of a scene created under separate focus conditions, said approximation data capable of generating a spectrum of photographs of said scene.

31. The computer readable medium as described in claim 30, wherein said approximation data is capable of generating a photographs of said scene outside of said spectrum of photographs.

32. The computer readable medium as described in claim 30, wherein said approximation data is comprised of a plurality of coefficients of a quadratic polynomial function for each subpixel in each of said spectrum of photographs, said coefficients form fitting said quadratic polynomial function to said dataset of photographs.

33. The computer readable medium as described in claim 30;

wherein said set of focus conditions comprise a range of focus depths.

34. The computer readable medium as described in claim 30, wherein said set of focus conditions comprise a range of depths of field.

35. The computer readable medium as described in claim 30, wherein said set of focus conditions comprise a region of focus conditions varying in two dimensions, including a first dimension varying in focus depth, and a second dimension varying in depth of field.

36. The computer readable medium as described in claim 30, wherein said approximation data is for at least one subpixel of said scene.

37. A computer system comprising:

a processor;

a display coupled to said processor;

a computer readable memory coupled to said processor and containing program instructions that, when executed, implement a method of varying focus in a scene, comprising;

a) obtaining a dataset of photographs of said scene, each of said dataset of photographs created under separate focus conditions within a range of focus conditions;

b) performing an approximation using said dataset of photographs that is capable of representing a spectrum of photographs of said scene, each of said spectrum of photographs having focus conditions within said range of focus conditions; and

c) recording a plurality of values associated with said approximation, said plurality of values capable of generating each of said spectrum of photographs.

38. The computer system as described in claim 37, wherein said method further comprises:

obtaining three photographs for said dataset of photographs.

39. The computer system as described in claim 37, wherein said method further comprises:

obtaining said dataset of photographs, each of said dataset of photographs created under separate focus conditions that vary in focus depth.

40. The computer system as described in claim 37, wherein said method further comprises:

obtaining said dataset of photographs, each of said dataset of photographs created under separate focus conditions that vary in depth of field.

41. The computer system as described in claim 37, wherein said method further comprises:

having said dataset of photographs define said range of focus conditions, said dataset of photographs having a first photograph with a minimum focus condition of −

1.0 and a second photograph with a maximum focus condition of +1.0.

42. The computer system as described in claim 37, wherein said method further comprises:

for each subpixel in said scene, obtaining a dataset of color values from said dataset of photographs;

for each subpixel in said scene, performing said approximation to determine a corresponding spectrum of color values from said spectrum of photographs by a corresponding quadratic polynomial function;

for each subpixel in said scene, recording a corresponding plurality of coefficients associated with said corresponding quadratic polynomial function.

43. The computer system as described in claim 42, wherein said method further comprises:

for each subpixel in said scene, least mean squares curve fitting a dataset of color values from said dataset of photographs to determine said corresponding plurality of coefficients.

44. The computer system as described in claim 42, wherein said method further comprises for each subpixel in said scene, recording said corresponding plurality of coefficients associated with said quadratic polynomial function, comprising:

Color Value(F, Focus Condition)=a₀F²+a₃F+a₅.

45. The computer as described in claim 37, wherein said method further comprises:

extrapolating from said dataset of photographs a plurality of photographs having focus conditions outside said range of focus conditions.

46. The computer system as described in claim 37, wherein said method further comprises:

selecting a selected focus condition within said range of focus conditions;

synthesizing a selected photograph for said selected focus condition from said plurality of values; and

displaying said selected photograph.