Sequential color display system with spoke synchronous frame rate conversion

• US 6,002,452 A
• Filed: 06/06/1996
• Issued: 12/14/1999
• Est. Priority Date: 06/08/1995
• Status: Expired due to Term

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Morgan, Dan
• Primary Examiner(s): Peng, John K.
• Assistant Examiner(s): DESIR, JEAN WICEL
• Application Number:
  US08/659,485
• Time in Patent Office: 1,286 Days
• Field of Search: 348/743, 348/742, 348/771, 348/739, 348/268, 348/269, 348/270, 348/271, 348/68, 348/69, 348/70
• US Class Current: 348/742
• CPC Class Codes: G02B 26/008 in the form of devices for effecting sequential colour changes, e.g. colour wheels
• CPC Class Codes: G09G 2340/0435 Change or adaptation of the frame rate of the video stream
• CPC Class Codes: G09G 2340/10 Mixing of images, i.e. displayed pixel being the result of an operation, e.g. adding, on the corresponding input pixels
• CPC Class Codes: H02P 23/18 Controlling the angular speed together with angular position or phase
• CPC Class Codes: H04N 9/3114 by using a sequential colour filter producing one colour at a time
• CPC Class Codes: H04N 9/312 Driving therefor driving of electronic spatial light modulators in displays other than projection devices G09G3/34, G09G3/36; control of liquid crystal elements G02F1/133; control of micromechanical modulators G02B26/08

Abstract

A sequential color display system (10) suited to receive data (20) at different rates without discarding or filtering video data. The mismatch of bandwidths between the input source video data and the output sequential color display is accommodated by retaining a modified synchronous operation. A color wheel (50) having a plurality of segments is utilized whereby the input frame rate in reference to the color wheel rate is always a ratio of integers. Using a digital micromirror device (44) spatial light modulator, no mixing of frame-to-frame bit planes is required during a colored segment. In the preferred embodiment, the ratio of integers is 7-to-6 for a 50 hertz input, such as a PAL system, or a 5-to-6 ratio for a 72 hertz input. The color wheel is maintained at about a 60 hertz rate.

Claims

1. A display system, comprising:

a spatial light modulator;

a light source providing light;

a color wheel rotating at a wheel rate and coloring said light, said colored light illuminating said spatial light modulator;

a logic circuit having an input receiving frames of data at a frame rate and communicating said data to said spatial light modulator; and

a control circuit detecting said frame rate, responsive to a vertical sync rate corresponding to said frame rate, and providing a wheel motor sync output at a rate as a function of said vertical sync rate of said frames of data, said sync output rate being unequal to said vertical sync rate when said vertical sync rate deviates from a predetermined rate, said wheel rate being a function of said sync output, and adjusting said color wheel rate so that said wheel rate compared to said frame rate is a ratio of integers, said integer ratio being other than one-to-one.

2. The display system as specified in claim 1 wherein said color wheel has a plurality of colored segments, wherein each said colored segment, but one or more, is illuminated for each said frame of data when said frame rate is less than said wheel rate.

3. The display system as specified in claim 1 wherein said color wheel has a plurality of colored segments, wherein at least one said colored segment is illuminated one more time than said other colored segments when said frame rate is greater than said wheel rate.

4. The display system as specified in claim 1 wherein said color wheel has multiple colored segments, wherein each said colored segment except one or more is illuminated equally in time for each said frame of data by said light source when said frame rate is less than said wheel rate.

5. The display system as specified in claim 1 wherein said color wheel has multiple colored segments, wherein each said colored segment except one or more is illuminated equally in time for each said frame of data by said light source when said frame rate is greater than said wheel rate.

6. The display system as specified in claim 1 wherein said color wheel has n colored segments, wherein no more than n-1 said segments are illuminated each said data frame when said frame rate is less than said wheel rate.

7. The display system as specified in claim 1 wherein said color wheel has n colored segments, wherein at least n+1 said segments are illuminated each said data frame when said frame rate is greater than said wheel rate.

8. The display system as specified in claim 1 wherein the ratio of said frame rate to said wheel rate is 7-to-6 when said frame rate is less than said wheel rate.

9. The display system as specified in claim 1 wherein the ratio of said frame rate to said wheel rate is 5-to-6 when said frame rate is greater than said wheel rate.

10. The display system as specified in claim 1 wherein said sync output rate is identical to said vertical sync rate when said frame rate is identical to said predetermined rate.

11. The method of operating a sequential display system, comprising:

a) utilizing a color wheel having a plurality of colored segments to color source light illuminating a spatial light modulator, said color wheel rotating at a wheel rate;

b) modulating said colored light with said spatial light modulator according to frames of data received at a frame rate; and

c) controlling said wheel rate by responding to a vertical sync rate corresponding to said frame rate, and providing a wheel motor sync output at a rate as a function of said vertical sync rate of said frames of data, said sync output rate being unequal to said vertical sync rate when said vertical sync rate deviates from a predetermined rate, said wheel rate being a function of said sync output, and adjusting said color wheel rate so that said wheel rate compared to said frame rate is a ratio of integers, wherein said ratio of integers is other than one-to-one.

12. The method as specified in claim 11 wherein said color wheel has at least six said colored segments.

13. The method as specified in claim 11 wherein a transition time between said frames of data occurs when a transition between said wheel colored segments is at a predetermined position relative to said source light.

14. The method as specified in claim 13 wherein said predetermined position is such that said source light illuminates said transition between said colored segments.