Pulse width modulation for spatial light modulator with split reset addressing

• US 5,497,172 A
• Filed: 06/13/1994
• Issued: 03/05/1996
• Est. Priority Date: 06/13/1994
• Status: Expired due to Term

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Doherty, Donald B., Miller, Rodney D., Gove, Robert J., Burton, Mark L.
• Primary Examiner(s): Weldon, Ulysses
• Application Number:
  US08/259,402
• Time in Patent Office: 631 Days
• Field of Search: 345/89, 345/108, 345/85, 345/185, 359/54-58
• US Class Current: 345/85
• CPC Class Codes: G09G 3/2014 by modulation of the duration of a single pulse during which the logic level remains constant
• CPC Class Codes: G09G 3/2018 by time modulation using two or more time intervals
• CPC Class Codes: G09G 3/2022 using sub-frames
• CPC Class Codes: G09G 3/2033 with splitting one or more sub-frames corresponding to the most significant bits into two or more sub-frames
• CPC Class Codes: G09G 3/34 by control of light from an independent source

Abstract

A method of implementing pulse-width modulated image display systems (10, 20) with a spatial light modulator (SLM) (15) configured for split-reset addressing. Display frame periods are divided into time slices. Each frame of data is divided into bit-planes, each bit-plane having one bit of data for each pixel element and representing a bit weight of the intensity value to be displayed by that pixel element. Each bit-plane has a display time corresponding to a number of time slices, with bit-planes of higher bit weights being displayed for more time slices. The bit-planes are further formatted into reset groups, each reset group corresponding to a reset group of the SLM (15). The display times for reset groups of more significant bits are segmented so that the data can be displayed in segments rather than for a continuous time. During loading, segments of corresponding bit-planes are temporally aligned from one reset group to the next. The display times for less significant bits are not segmented but are temporally aligned to the extent possible without loading conflicts.

Claims

1. A method of loading frames of data to a spatial light modulator having individually addressable pixel elements, for a pulse width modulated display, comprising the steps of:

dividing the display period for each said frame of data into a number of time slices;

formatting each frame of data into bit-planes, each bit-plane having one bit of data for each of said pixel elements, and each bit-plane representing a bit-weight of the intensity value to be displayed by that pixel element, and each bit-plane having a display time corresponding to a number of said time slices;

sub-formatting said bit-planes into reset groups, each reset group having data for a group of pixel elements to be loaded at a different time from other pixel elements, wherein said reset groups are defined by one memory cell providing data to more than one pixel element;

segmenting into segments, the display times of reset groups of bit-planes of one or more of the more significant bit weights;

front-frame loading said segments at the beginning of said frame period, such that, for all reset groups, segments having the same bit weight are loaded at substantially the same time;

mid-frame loading the reset groups of bit-planes of one or more of the less significant bits at the middle of said frame period; and

end-frame loading the remaining of said segments at the end of said frame period, such that for all reset groups, segments having the same bit-weight are loaded at substantially the same time.

2. The method of claim 1, wherein said front-frame and said end-frame loading steps are performed by separating the loading for each said reset group by one of said time slices.

3. The method of claim 1, wherein each of said time slices has a duration of the display time of the least significant bit of said intensity values.

4. The method of claim 1, wherein each of said time slices has a duration of twice the display time of the least significant bit of said intensity values.

5. The method of claim 1 wherein said segmenting step is performed such that the number of segments is the number of said time slices less the number of loads of said bit-planes of said less significant bits.

6. The method of claim 1, wherein said front-frame loading step is performed by using one of said segments as a buffer segment, which varies in size among reset groups so as to permit substantial alignment during said mid-frame loading.

7. The method of claim 1, wherein all segments of the same bit-plane have the same number of time slices.

8. The method of claim 1, wherein all segments of the same reset groups have the same number of time slices.

9. The method of claim 1, wherein said front-frame loading and said end-frame loading are the same sequence for all of said reset groups.

10. The method of claim 1, wherein said mid-frame loading is performed in a different sequence for different of said reset groups.

11. The method of claim 1, wherein said more significant bits are bit greater than bit 2.

12. The method of claim 11, wherein said front-frame loading step is performed by using one of said segments as a buffer segment, which varies in size among reset groups so as to permit substantial alignment of bit 3.

13. The method of claim 1, wherein said front-frame loading, mid-frame loading, and end-frame loading are sequenced in n series of every nth reset group.