Light modulator having pixel memory decoupled from pixel display

• US 7,362,316 B2
• Filed: 02/27/2002
• Issued: 04/22/2008
• Est. Priority Date: 02/22/2002
• Status: Active Grant

• Current Assignee: Intel Corporation
• Original Assignee: Intel Corporation
• Inventors: Willis, Thomas E.
• Primary Examiner(s): Hjerpe; Richard
• Assistant Examiner(s): ABDULSELAM, ABBAS I
• Application Number:
  US10/086,010
• Publication Number:
  US 20030160803A1
• Time in Patent Office: 2,246 Days
• Field of Search: 345/691, 345/690, 345/84, 345/87, 345/93, 345/204, 345/98, 345/698, 359223-224, 359290-291, 369/112.01, 369/112.02, 369/110.01, 348/743, 348/750, 348/771
• US Class Current: 345/204
• CPC Class Codes: G09G 2300/0809 Several active elements per pixel in active matrix panels
• CPC Class Codes: G09G 2300/0828 forming a digital to analog [D/A] conversion circuit
• CPC Class Codes: G09G 2300/0857 Static memory circuit, e.g. flip-flop
• CPC Class Codes: G09G 2310/0259 with use of an analog or digital ramp generator in the column driver or in the pixel circuit
• CPC Class Codes: G09G 2310/027 Details of drivers for data electrodes, the drivers handling digital grey scale data, e.g. use of D/A converters
• CPC Class Codes: G09G 2330/08 Fault-tolerant or redundant circuits, or circuits in which repair of defects is prepared
• CPC Class Codes: G09G 2340/0407 Resolution change, inclusive of the use of different resolutions for different screen areas
• CPC Class Codes: G09G 2360/18 Use of a frame buffer in a display terminal, inclusive of the display panel
• CPC Class Codes: G09G 3/2003 Display of colours specific for liquid crystal displays G09G3/3607
• 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 3/3622 using a passive matrix G09G3/3674 - G09G3/3696 take precedence
• CPC Class Codes: G09G 3/3648 using an active matrix G09G3/367 - G09G3/3696 take precedence
• CPC Class Codes: G09G 3/3692 suitable for passive matrices only
• CPC Class Codes: G09G 3/3696 Generation of voltages supplied to electrode drivers
• CPC Class Codes: G09G 5/06 using colour palettes, e.g. look-up tables

Abstract

A light modulator such as an SLM, in which the pixel data array is decoupled from the pixel display array. The pixel data array can be located externally, permitting significant reduction in the circuitry present under each pixel of the display, in turn permitting significant reduction in display pixel size and independent scaling of memory cell size and display cell size.

Claims

1. A spatial light modulator comprising:

a multi-pixel display array on a first die, a multi-pixel memory array on a second die separate from the first die, the multi-pixel memory array having pixel storage cells, and wherein at least some pixels of the multi-pixel memory array are disposed outside the multi-pixel display array such that the multi-pixel memory array is physically decoupled from the multi-pixel display array;

at least one local pulse width modulation drive circuit coupled to at least one of the pixel storage cells;

a global counter coupled to the local pulse width modulation drive circuit to provide a global count value thereto, wherein;

the display pixels of the multi-pixel display array comprise first display pixels of a first color, and second display pixels of a second color;

the global counter includes,

a first global counter coupled to the local pulse width modulation drive circuits of the first display pixels, and

a second global counter coupled to the local pulse width modulation drive circuits of the second display pixels.

2. The spatial light modulator of claim 1 wherein all of the pixels of the memory array are disposed outside the display array.

3. The spatial light modulator of claim 1 wherein:

the display pixels of the multi-pixel display array further comprise third pixels of a third color.

4. The spatial light modulator of claim 3 wherein:

the global counter further includes,

a third global counter coupled to the local pulse width modulation drive circuits of the third display pixels.

5. The spatial light modulator of claim 1 wherein;

the multi-pixel display array includes display pixels of at least two different colors; and

the global counter is adapted to count up to two respective different values and is switcheably coupled to the respective different color display pixels to provide global counter values to their local pulse width modulation drive circuits in a time-slice manner.

6. The spatial light modulator of claim 5 wherein:

the multi-pixel display array includes display pixels of three different colors.

7. The spatial light modulator of claim 1, wherein the spatial light modulator comprises a liquid crystal on silicon display.

8. The spatial light modulator of claim 1, wherein each of the pixel storage cells is associated with one pixel of the multi-pixel display array.

9. The spatial light modulator of claim 1, wherein the first die is formed using a first semiconductor technology and the second die is formed using a second semiconductor technology.

10. A method of manufacturing a light modulator, the method comprising:

constructing, on a first die and in a first area of the light modulator, a pixel display array including multiple display pixels, and constructing, on a second die separate from the first die and in a second area of the light modulator that is physically decoupled and substantially non-overlapping with the first area, a pixel memory array including multiple pixel storage cells;

constructing, within each of a plurality of the display pixels, a pulse width modulation driver circuit;

constructing a counter having an output coupled to each of the plurality of display pixels, and constructing, within each of the pulse width modulation driver circuits, a comparator having a first input coupled to the output of the counter and a second input coupled to receive a pixel data value from the pixel memory array, configuring the comparator to determine whether the pixel data value is greater-than-or-equal-to the counter output; and

constructing a lookup table to provide non-linear response in the pulse width modulation.

11. A method of operating a light modulator, the method comprising:

performing a digital function on a pixel data value and a present counter value to generate one of a first result or a second result, wherein a pixel memory array is physically decoupled from a pixel display array to hold the pixel data value;

in response to the first result, activating the pixel cell;

in response to the second result, deactivating the pixel cell;

detecting that a pixel memory cell in the pixel memory array is not operating correctly;

responsively logically replacing that memory cell with a redundant memory cell; and

incrementing the counter value over time from 0 to N-1, wherein N is a number of bits of color depth represented in the pixel data value; and

then wrapping back to 0.

12. The method of claim 11 wherein:

the digital function comprises a comparison.

13. The method of claim 11 further comprising:

performing non-linear pulse width modulation.

14. The method of claim 11 wherein:

the digital function is performed outside the pixel cell.

15. The method of claim 11 wherein:

the digital function comprises using the present counter value to index into a lookup table.

16. An article of manufacture comprising:

a machine-accessible medium including data that, when accessed by a machine system, cause the machine system to perform the method of claim 11.

17. The article of manufacture of claim 16 wherein the machine-accessible medium further includes data that, when accessed by the machine system, cause the machine system to perform the method of claim 12.

18. A projection device comprising:

a polarization beam splitter;

a first light modulator coupled in optical contact with the polarization beam splitter, the first light modulator including,

a first pixel display array in a first region of the first light modulator, and

a first pixel memory array in a second region substantially not overlapping the first region of the first light modulator, such that at least a plurality of pixel memory cells of the first pixel memory array lie outside the first region of the first light modulator and the first and second regions are not physically coupled; and

a second light modulator coupled in optical contact with the polarization beam splitter, the second light modulator including,

a second pixel display array in a first region of the second light modulator, and

a second pixel memory array in a second region substantially not overlapping the first region of the second light modulator, such that at least a plurality of pixel memory cells of the second pixel memory array lie outside the first region of the second light modulator.

19. The projection device of claim 18, wherein the first light modulator comprises a liquid crystal on silicon display.

20. The projection device of claim 18, wherein each of the pixel memory cells of the first pixel memory array is associated with one pixel display cell of the first pixel display array.