Non-terminating pulse width modulation for displays

• US 6,573,951 B1
• Filed: 10/06/1999
• Issued: 06/03/2003
• Est. Priority Date: 10/09/1998
• Status: Expired due to Term

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Hewlett, Gregory J., Doherty, Donald B.
• Primary Examiner(s): Miller, John
• Assistant Examiner(s): YENKE, BRIAN P
• Application Number:
  US09/413,582
• Time in Patent Office: 1,336 Days
• Field of Search: H04/N.574, H04/N.912, 348/742, 348/743, 348/750, 348/759, 348/770, 348/771, 345/84, 345/88, 345/89, 345/691, 345/692, 345/693
• US Class Current: 348/770
• CPC Class Codes: H04N 5/7458 the modulator being an array of deformable mirrors, e.g. digital micromirror device [DMD]
• CPC Class Codes: H04N 9/3114 by using a sequential colour filter producing one colour at a time
• CPC Class Codes: H04N 9/3123 using pulse width modulation

Abstract

A method for using pulse-width modulation in displays. A series of PWM sequences is established. Each subsequent sequence clears the previous sequence before it, eliminating the need for a separate clearing reset at the end of the previous sequence. This allows for use of spoke bits in color-sequential systems. In non-color sequential systems and rapid color-switching systems it allows the sequence for one frame to flow directly into the sequence for the next frame.

Claims

1. A method of displaying image data using a spatial light modulator, the method comprising:

establishing an interval between a first division point and a second division point;

receiving a word of image data for each pixel of an image, each word comp of at least two data bits each said data bit having a significance;

for each said data bit;

loading said data bit into a said spatial light modulator; and

resetting said spatial light modulator to respond to said loaded data bit to begin a display period of said loaded data bit and to end a display period of a previously loaded data bit;

wherein all of said data bits are displayed during said interval, said display period for each said data bit determined by said significance of said data bit except for said display period of a last data bit in said word, which display period is terminated at said second division point such that said display period of said last data bit is not equal to a period determined by the significance of said last display bit.

2. The method of claim 1, said establishing an interval between a first division point and a second division point comprising:

establishing an interval between a first division point defined by a color switching boundary of a color wheel and a second division point defined by a color switching boundary of a color wheel.

3. The method of claim 2, comprising:

displaying spoke bits during said color switching boundary of said color wheel.

4. The method of claim 1, said establishing an interval between a first division point and a second division point comprising:

establishing an interval between a first division point defined by an image frame boundary and a second division point defined by an image frame boundary.

5. The method of claim 1, said establishing an interval between a first division point and a second division point comprising:

establishing an interval between a first division point defined by a color switching boundary and a second division point defined by a color switching boundary.

6. The method of claim 1, said establishing an interval between a first division point and a second division point comprising:

establishing an interval between a first division point defined by a switching LED illumination system and a second division point defined by said switching LED illumination system.