Light modulator having pixel memory decoupled from pixel display

• US 20080062158A1
• Filed: 10/30/2007
• Published: 03/13/2008
• Est. Priority Date: 02/27/2002
• Status: Active Grant

• Current Assignee: Thomas Willis
• Original Assignee: Thomas Willis
• Inventors: Willis, Thomas
• Granted Patent: US 7,956,857 B2
• Time in Patent Office: Days
• US Class Current: 345/204
• CPC Class Codes: G09G 2330/08 Fault-tolerant or redundant circuits, or circuits in which repair of defects is prepared
• 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 formed on a first die; and

a multi-pixel memory array formed on a second die separate from the first die, the multi-pixel memory array having pixel storage cells, and wherein the multi-pixel memory array is physically decoupled from the multi-pixel display array.

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, further comprising:

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

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

4. The spatial light modulator of claim 3 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; and

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.

5. The spatial light modulator of claim 4, wherein the display pixels of the multi-pixel display array further comprise third pixels of a third color.

6. The spatial light modulator of claim 5, wherein the global counter further includes a third global counter coupled to the local pulse width modulation drive circuits of the third display pixels.

7. The spatial light modulator of claim 3, wherein the multi-pixel display array includes display pixels of at least two different colors;

and

the global counter is 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.

8. The spatial light modulator of claim 7, wherein the multi-pixel display array includes display pixels of three different colors.

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

10. 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.

11. The spatial light modulator of claim 1, wherein the multi-pixel display array is formed using a first semiconductor technology and the multi-pixel memory array is formed using a second semiconductor technology.

12. A spatial light modulator comprising:

control logic;

a pixel memory array coupled to the control logic and formed on a first die; and

a pixel display array coupled to the control logic and the pixel memory array, and formed on a second die, wherein the first and second die are physically decoupled and substantially non-overlapping, the pixel display array comprising a plurality of pixel display cells, each having disposed within its area an associated pulse width modulation driver circuit.

13. The spatial light modulator of claim 12, wherein:

the control logic comprises a counter to provide a count value;

the pulse width modulation driver circuit comprises a comparator coupled to compare the count value to a pixel value stored in an associated pixel array cell of the pixel memory array.

14. The spatial light modulator of claim 12, wherein the pixel memory array comprises:

more memory cells than the pixel display array has pixel display cells; and

a redundancy mechanism in the pixel memory array.

15. The spatial light modulator of claim 12, wherein the spatial light modulator comprises a liquid crystal on silicon display.

16. The spatial light modulator of claim 12, wherein each of a plurality of pixel memory cells is associated with one pixel display cell of the pixel display array.

17. A 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 of a first die stores the pixel data value and the pixel memory array is physically decoupled from a pixel display array of a second die;

activating or deactivating a pixel cell of the pixel display array based on the digital function; and

logically replacing a pixel memory cell with a redundant memory cell if the pixel memory cell is detected to not be operating correctly.

18. The method of claim 17, further comprising incrementing the present counter value 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.

19. The method of claim 17, wherein the digital function comprises using the present counter value to index into a lookup table.