Method and system for field sequential color image capture using color filter array

• US 6,690,422 B1
• Filed: 11/03/1999
• Issued: 02/10/2004
• Est. Priority Date: 11/03/1999
• Status: Expired due to Fees

• Current Assignee: Sharp Laboratories of America Incorporated (Hon Hai Precision Industry Co., Ltd.)
• Original Assignee: Sharp Laboratories of America Incorporated (Hon Hai Precision Industry Co., Ltd.)
• Inventors: Daly, Scott J., Feng, Xiaofan
• Primary Examiner(s): Garber, Wendy R.
• Assistant Examiner(s): MISLEH, JUSTIN P
• Application Number:
  US09/433,540
• Time in Patent Office: 1,560 Days
• Field of Search: 348/268, 348/269, 348/270, 348/271, 348/272, 348/273, 348/277, 348/280, 348/317, 348/612, 348/620, 348/218.1, 348/490, 348/608, 348/70, 348/234, 348/106, 358/500, 358/503, 358/505, 358/513, 358/515, 358/512, 382/260
• US Class Current: 348/273
• CPC Class Codes: H04N 23/84 for processing colour signals
• CPC Class Codes: H04N 25/134 based on three different wavelength filter elements

Abstract

A method of field sequential color image capture includes: optically capturing a scene frame-by-frame; filtering the scene through an active color shutter to produce a first color component set having plural first color components therein; detecting the scene with a color filter array area sensor, wherein each first color component of the first color component set of the scene is detected at different points in time within a frame; dividing the detected scene into a second color component set having plural second color components therein; aligning the second color component set in time for each frame interval; and combining the stored second color components into a frame image. A system for capturing a field sequential color image includes an optical capture mechanism for capturing a scene frame-by-frame in frame intervals which operates at a predetermined shutter speed; a color shutter for producing a first color component set having plural first color components therein, thereby modifying the spectral transmission of the scene as a function of time; a CFA area sensor for sensing the first color components, wherein each first color component of the scene is detected at a different point in time within a frame; an array field selector for dividing the scene into a second color component set having plural second color components therein; and a field-to-frame combiner for combining the second color components into a frame image.

Claims

1. A method of field sequential color image capture comprising:

optically capturing a scene frame-by-frame;

filtering the scene through an active color shutter to produce a first color component set having plural first color components therein, thereby modifying the spectral transmission of the scene as a function of time, wherein said modifying includes operating a frame control clock at a first predetermined rate, operating a color field clock at a second predetermined rate, and operating an interlaced array field selector at a third predetermined rate, wherein the third predetermined rate is equal to the second predetermined rate, and wherein the second predetermined rate is greater than the first predetermined rate;

detecting the scene with a color filter array area sensor, wherein each first color component of the first color component set of the scene is detected at different points in time within a frame;

dividing the detected scene into a second color component set having plural second color components therein;

aligning the second color component set in time for each frame interval;

storing each second color component in a memory unit;

combining the stored second color components into a frame image; and

processing the frame image for color reproduction and format.

2. The method of claim 1 wherein said dividing includes dividing the scene into Y and combined U and V color components.

3. The method of claim 2 which includes, after said storing, temporally filtering at least some of the second color components.

4. The method of claim 3 wherein said filtering includes temporally filtering and spatially interpolating the U and V color components.

5. The method of claim 3 wherein said filtering includes temporally and spatially filtering the Y color component.

6. The method of claim 1 wherein said operating includes setting the second predetermined rate to about 2×

that of the first predetermined rate.

7. The method of claim 1 wherein said filtering the scene includes filtering the scene to capture B, Y and R first color components.

8. The method of claim 1 wherein said filtering the scene to produce a first color component set includes filtering the scene to acquire green, red and blue first color components.

9. The method of claim 1 wherein said filtering the scene to produce a first color component set includes filtering the scene to acquire cyan-green and green-yellow first color components and spatially interleaving the cyan-green and green-yellow first color components.

10. The method of claim 1 wherein said dividing includes dividing the scene into a luminance color component at a first frame time and dividing the scene into a UV color component at a second frame time.

11. The method of claim 1 wherein said combining includes spatially interleaving the second color components.

12. A method of field sequential color image capture comprising:

optically capturing a scene frame-by-frame;

filtering the scene through an active color shutter to produce a first color component set having plural first color components therein, thereby modifying the spectral transmission of the scene as a function of time, wherein said modifying includes operating a frame control clock at a first predetermined rate, operating a color field clock at a second predetermined rate, and operating an interlaced array field selector at a third predetermined rate, wherein the third predetermined rate is equal to the second predetermined rate, and wherein the second predetermined rate is greater than the first predetermined rate;

detecting the scene with a color filter array area sensor, wherein each first color component of the first color component set of the scene is detected at different points spatially in the image through two different color filters and is detected at different points in time within a frame; and

dividing the detected scene into a second color component set having plural second color components therein.

13. The method of claim 12 wherein said dividing includes dividing the scene into Y and combined U and V color components.

14. The method of claim 13 which includes, after said storing, temporally filtering at least some of the second color components.

15. The method of claim 14 wherein said filtering includes temporally filtering and spatially interpolating the U and V color components.

16. The method of claim 14 wherein said filtering includes temporally and spatially filtering the Y color component.

17. The method of claim 16 wherein said operating includes setting the second predetermined rate to about 2×

that of the first predetermined rate.

18. The method of claim 12 wherein said filtering the scene includes filtering the scene to capture B, Y and R first color components.

19. The method of claim 12 wherein said filtering the scene to produce a first color component set includes filtering the scene to acquire green, red and blue first color components.

20. The method of claim 12 wherein said filtering the scene to produce a first color component set includes filtering the scene to acquire cyan-green and green-yellow first color components and spatially interleaving the cyan-green and green-yellow first color components.

21. The method of claim 12 wherein said dividing includes dividing the scene into a luminance color component at a first frame time and dividing the scene into a UV color component at a second frame time.

22. The method of claim 12 wherein said combining includes spatially interleaving the second color components.

23. The method of claim 12 which further includes:

aligning the second color component set in time for each frame interval;

storing each second color component in a memory unit;

combining the stored second color components into a frame image; and

processing the frame image for color reproduction and format.

24. A system for capturing a field sequential color image, comprising:

an optical capture mechanism for capturing a scene frame-by-frame in frame intervals which operates at a predetermined shutter speed;

a color shutter for producing a first color component set having plural first color components therein, thereby modifying the spectral transmission of the scene as a function of time;

a CFA area sensor for sensing said first color components, wherein each first color component of the scene is detected at a different point in time within a frame;

an array field selector for dividing the scene into a second color component set having plural second color components therein;

a frame clock operating at a first predetermined rate,

a color field control clock, operating at a second predetermined rate under control of said frame clock, for controlling said color shutter and said area sensor at a second predetermined rate, wherein and said array field selector operates at a third predetermined rate;

multiple memory locations for storing each color component; and

a field-to-frame combiner for combining the stored second color components into a frame image.

25. The system of claim 24 wherein said array field selector divides the scene into Y and combined U and V color components.

26. The system of claim 25 which includes temporal and spatial filters for temporally and spatially filtering at least some of the second color components.

27. The system of claim 26 which includes temporal filters and spatial interpolators for temporally filtering and spatially interpolating the U and V color components.

28. The system of claim 26 which includes temporal and spatial filters for temporally and spatially filtering the Y color component.

29. The system of claim 24 wherein said active color filter includes an LCD color field shutter having plural shutter states.

30. The system of claim 29 wherein said LCD color field shutter changes state at said third predetermined rate.

31. The system of claim 24 wherein said third predetermined rate equal to said second predetermined rate, and wherein said second predetermined rate is 2×

that of said first predetermined rate.

32. The method of claim 24, wherein said first color components are G, R and B.

33. The system of claim 24 which further includes a color reproduction processor for processing the frame image for color reproduction and format.