Method and system for field sequential color image capture

• US 6,697,109 B1
• Filed: 05/06/1999
• Issued: 02/24/2004
• Est. Priority Date: 05/06/1999
• 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.
• Primary Examiner(s): Garber, Wendy R.
• Assistant Examiner(s): MISLEH, JUSTIN P
• Application Number:
  US09/306,685
• Time in Patent Office: 1,755 Days
• Field of Search: 348/272, 348/273, 348/277, 348/270, 348/280, 348/317, 348/266, 348/267, 348/268, 348/269, 348/612, 348/620, 348/218.1, 348/490, 348/70, 348/607, 348/608, 348/613, 348/234, 348/453, 348/456, 348/488, 348/503, 348/513, 358/500, 358/503, 358/505, 358/512, 358/513, 358/515, 382/260, 349/106
• US Class Current: 348/268
• CPC Class Codes: H04N 23/125 Colour sequential image capture, e.g. using a colour wheel

Abstract

A method of field sequential color image capture includes optically capturing a scene; filtering the scene through an active color filter to product first color components, thereby modifying the spectral transmission of the scene as a function of time; detecting the scene with a single, monochrome sensor and dividing the scene into multiple second color components, whereby each first color component of the scene is detected at a different point in time; aligning the second color components in time for each frame interval; storing each 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. A system for capturing a field sequential color image, includes an optical capture mechanism for capturing a scene frame-by-frame in frame intervals; an active color filter for producing multiple first color components; a single monochrome area sensor; an array field selector for dividing the scene into multiple second color components; multiple memory locations for storing each color component; a field-to-frame combiner for combining the stored second color components into a frame image; and a color reproduction processor for processing the frame image for color reproduction and format.

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 filter to product a first color component set having plural first color components therein, thereby modifying the spectral transmission of the scene as a function of time, including operating a color field clock at a first predetermined rate and operating a frame control clock at a second predetermined rate, wherein the first predetermined rate is greater than the second predetermined rate, and wherein the first predetermined rate is set to about 2X that of the second predetermined rate;

detecting the scene with a single, monochrome sensor, wherein each first color component of the first color component set of the scene is detected at a different point in time within a frame;

dividing the detected scene into a second color component set having plural second color components therein, including temporally dividing the scene into U, Y and V color components;

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 which includes, after said storing, filtering at least some of the second color components to reduce noise.

3. The method of claim 2 wherein said filtering includes temporally and spatially filtering the U and V color components.

4. The method of claim 2 wherein said filtering includes temporally and spatially filtering the Y color component.

5. The method of claim 1 wherein said operating includes setting the first predetermined rate to about 3X that of the second predetermined rate.

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

7. The method of claim 6 wherein said dividing includes storing B, Y and R first color components and differenfiating B-Y to form a U second color component and differentiating R-Y to form a V color component.

8. The method of claim 7 wherein said differentiating is temporal differentiating.

9. The method of claim 1 wherein said capturing includes directly capturing a luminance color component.

10. The method of claim 1 wherein said capturing includes capturing each first color component of the first color component set in a time interval that is less than the inverse of the number of first color components in the first color component set applied to a per-frame capture cycle time for the first color component set.

11. 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 exposure duration;

an active color filter 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 single monochrome 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 color field control clock for controlling said active color filter, said area sensor and said array field selector at a first predetermined rate and for aligning the second color components in time for each frame interval;

multiple memory locations for storing each color component;

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

a color reproduction processor for processing the frame image for color reproduction and format; and

a frame clock for controlling said color field clock, said memory locations, and said field-to-frame combiner at a second predetermined rate, wherein said first predetermined rate is greater than said second predetermined rate.

12. The system of claim 11 wherein said array field selector divides the scene into U, Y and V color components.

13. The system of claim 12 which includes temporal and spatial filters for temporally and spatially filtering at least some of the second color components.

14. The system of claim 13 which includes temporal and spatial filters for temporally and spatially filtering the U and V color components.

15. The system of claim 13 which includes temporal and spatial filters for temporally and spatially filtering the Y color component.

16. The system of claim 11 wherein said first predetermined rate is 3X that of the said second predetermined rate.

17. The system of claim 11 wherein said first predetermined rate is 2X that of the said second predetermined rate.

18. The system of claim 11 wherein said color field clock operates at a time interval less than the inverse of the number of said first color components in said first color component set, applied to a per-frame capture cycle time for the first color component set, to reduce color lag as said predetermined shutter speed increases.

19. The method of claim 11 wherein said first color components are B, Y and R.

20. The method of claim 19 wherein said array field selector stores B, Y and R first color components and differentiates B-Y to form a U second color component and differentiates R-Y to form a V color component.

21. The method of claim 19 wherein said array field selector stores B, Y and R first color components and temporally differentiates B-Y to form a U second color component and temporally differentiates R-Y to form a V color component.