Method and apparatus for sequential color imaging

• US 5,448,314 A
• Filed: 01/07/1994
• Issued: 09/05/1995
• Est. Priority Date: 01/07/1994
• Status: Expired due to Term

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Sampsell, Jeffrey B., Doherty, Donald B., Marshall, Stephen W., Davis, Carl W., Gove, Robert J., Sextro, Gary L., Egan, Joseph G., Heimbuch, Scott D.
• Primary Examiner(s): Groody, James J.
• Assistant Examiner(s): HSIA, SHERRIE Y
• Application Number:
  US08/179,028
• Time in Patent Office: 606 Days
• Field of Search: 348/743, 348/742, 348/771, 348/268, 348/270, 348/269, 358/42, 358/230
• US Class Current: 348/743
• CPC Class Codes: G09G 2310/0235 Field-sequential colour display
• CPC Class Codes: G09G 3/2025 the sub-frames having all the same time duration
• CPC Class Codes: G09G 3/34 by control of light from an independent source
• CPC Class Codes: G09G 3/346 based on modulation of the reflection angle, e.g. micromirrors micromirrors devices per se G02B26/0833
• CPC Class Codes: H04N 9/30 using solid-state colour display devices
• CPC Class Codes: H04N 9/3114 by using a sequential colour filter producing one colour at a time

Abstract

A sequential color system is provided in which a processor (22) is coupled to a memory (24) and a receiver (27). Images are generated by shining light from a light source (28) through a color wheel (30) and onto DMD array (26). Light from the DMD array (26) is shone on screen (32). By adjusting the speed and make-up of color wheel (30) color separation is greatly reduced or eliminated. Also there are techniques for sequential imaging which may be applied to other technologies, such as CRT technologies.

Claims

1. A method of sequential imaging, comprising the steps of:

generating at least two color subframes of a first color during one image frame;

generating at least two color subframes of a second color during said one image frame; and

generating at least two color subframes of a third color during said one image frame, wherein said generating of said first, second and third colors is accomplished by pulse width modulation of individual elements of a spatial light modulator for predetermined on and off times.

2. The method of claim 1, and further comprising the steps of:

shining light through a color wheel onto said spatial light modulator; and

rotating the color wheel to generate each of the color subframes.

3. The method of claim 2, wherein the color wheel is rotated at least twice during the image frame.

4. The method of claim 2, wherein the color wheel is rotated once during the image frame.

5. A method of sequential imaging, comprising the steps of:

generating at least two color subframes of a first color during one image frame;

generating at least one color subframe of a second color during said one image frame; and

generating at least one color subframe of a third color during said one image frame, wherein said generating of said first, second and third colors is accomplished by pulse width modulation of individual elements of a spatial light modulator for predetermined on and off times.

6. The method of claim 5, wherein said color subframes of the first color are generated at the beginning and end of the image frame.

7. The method of claim 6, wherein:

two color subframes of the first color are generated;

one color subframe of the third color is generated; and

two color subframes of the second color are generated, one each of the color subframes of the second color being generated before and after the color subframe of the third color.

8. The method of claim 5, and further comprising the steps of:

shining light through a color wheel onto said said spatial light modulator; and

rotating the color wheel to generate each of the color subframes.

9. The method of claim 5, wherein the color wheel is rotated at least twice during the image frame.

10. The method of claim 5, wherein the color wheel is rotated once during the image frame.

11. The method of claim 5, and further comprising the steps of:

distributing the on times within each color subframe such that said on times occur as near in time as possible as the on times within adjacent color subframes.

12. A method of sequential imaging, comprising the steps of:

generating a color subframe of a first color during one image frame;

after the first color subframe, generating a color subframe of a second color during said one image frame;

after the second color subframe, generating a color subframe of a third color during said one image frame; and

during the next image frame, generating the color subframes in reverse order.

13. The method of claim 12, and further comprising the steps of:

shining light through a color wheel onto a spatial light modulator; and

rotating the color wheel to generate each of the color subframes.

14. A sequential imaging system, comprising:

a light source;

a color wheel through which light from said light source is shone;

a spatial light modulator including a plurality of individual elements for receiving the light through said color wheel and operable to generate images using said light;

a processor operable to control said light source, said color wheel, and said spatial light modulator such that at least two color subframes of a first color are generated during said one image frame, at least one color subframe of a second color is generated during said one image frame and at least one color subframe of a third color is generated during said one image frame, wherein generating of said first, second and third colors is accomplished by said processor controlling the pulse width modulation of said individual elements of said spatial light modulator for predetermined on and off times.

15. The system of claim 14, wherein said color subframes of the first color are generated at the beginning and end of the image frame.

16. The system of claim 14, wherein said color wheel comprises:

a first area of the first color, the size of which is approximately one-third of the useful area of said color wheel;

a second area of the second color, the size of which is approximately one-sixth of the useful area of said color wheel;

a third area of the third color, the size of which is approximately one-third of the useful area of said color wheel; and

a fourth area of the second color, the size of which is approximately one-sixth of the useful area of said color wheel, said second and fourth areas being separated angularly by said third area.

17. The system of claim 14, wherein the color wheel is rotated at least twice during the image frame.

18. The system of claim 14, wherein said color wheel is rotated once during the image frame.

19. The system of claim 14, wherein said processor distributes the on times within each color subframe as near in time as possible to on times of adjacent color subframes.

20. The system of claim 14, wherein the system is a split reset DMD system having a plurality of groups of individual elements, wherein there are two color subframes for each color during the image frame, and wherein said individual elements are controlled with pulse width modulation bits for the predetermined on and off times, and further comprising circuitry operable to:

load one half of said bits for each color during a first respective color subframe for each color;

reset said individual bits at the end of each color subframe; and

load the remaining portion of said bits for each color during a second respective color subframe for each color.