Lcos column memory effect reduction

• US 20040169754A1
• Filed: 12/08/2003
• Published: 09/02/2004
• Est. Priority Date: 06/08/2001
• Status: Active Grant

• Current Assignee: InterDigital Patent Holdings, Inc. (InterDigital, Inc.)
• Original Assignee: Thomson Licensing (Vantiva SA)
• Inventors: Willis, Donald Henry
• Granted Patent: US 7,411,573 B2
• Time in Patent Office: Days
• US Class Current: 348/308
• CPC Class Codes: G09G 2310/0248 Precharge or discharge of column electrodes before or after applying exact column voltages
• CPC Class Codes: G09G 2320/0257 Reduction of after-image effects
• CPC Class Codes: G09G 3/3648 using an active matrix G09G3/367 - G09G3/3696 take precedence
• CPC Class Codes: G09G 3/3688 suitable for active matrices only

Abstract

The invention concerns a method for reducing the effect of column memory. The method includes the steps of activating (212) one of a plurality of row electrodes, selectively applying (214) a video input signal to a plurality of column electrodes, and setting (216) at least one of the plurality of column electrodes to a substantially constant voltage prior to activating a subsequent row electrode. Ine one arrangement, the substantially constant voltage can correlate to a flat field. The method can also include repeating the steps of activating one of the plurality of row electrodes step, selectively applying the video input signal step, and setting at least one of the plurality of column electrodes to the substantially constant voltage step in which the steps can be performed in a liquid crystal on silicon imager.

Claims

1. A method for reducing the effect of column memory in a video imager, comprising the steps of:

activating one of a plurality of row electrodes;

selectively applying a video input signal to a plurality of column electrodes; and

setting at least one of the plurality of column electrodes to a substantially constant voltage prior to activating a subsequent row electrode.

2. The method according to claim 1, wherein the substantially constant voltage correlates to a flat field.

3. The method according to claim 1, further comprising the steps of:

cyclically repeating the activating, selectively applying and setting steps; and

,

using said cyclically repeating steps to control a liquid crystal on silicon imager.

4. The method according to claim 3, wherein at least a portion of said activating steps is performed sequentially.

5. The method according to claim 3, wherein at least a portion of said activating steps is performed non-sequentially.

6. The method according to claim 1, wherein said activating step further comprises the step of activating a row electrode associated with an active display line.

7. The method according to claim 1, wherein said step of setting at least one of the plurality of column electrodes to a substantially constant voltage further comprises the steps of:

writing the video input signal to a memory;

activating the subsequent row electrode once the plurality of column electrodes are set to the substantially constant voltage; and

selectively applying the video input signal from the memory to the plurality of column electrodes.

8. The method according to claim 7, wherein said step of setting at least one of the plurality of column electrodes to a substantially constant voltage further comprises the step of activating a subsequent row electrode associated with a hidden display line such that a substantially constant brightness associated with the substantially constant voltage can be displayed on the hidden display line.

9. The method according to claim 1, wherein said step of setting at least one of the plurality of column electrodes to a substantially constant voltage comprises the steps of:

prior to activating the subsequent row electrode, applying a pulse to a terminal connected to at least one switch, wherein the pulse activates the switch; and

setting the plurality of column electrodes to the substantially constant voltage through the at least one switch.

10. A system for reducing the effect of column memory, comprising:

a controller, wherein the controller is programmed to activate one of a plurality of row electrodes;

a switch control to selectively apply a video input signal to a plurality of column electrodes; and

a circuit for setting at least one of the plurality of column electrodes to a substantially constant voltage prior to the controller activating a subsequent row electrode.

11. The system according to claim 10, wherein the substantially constant voltage correlates to a flat field.

12. The system according to claim 10, wherein the controller is further programmed to repeatedly activate one of the plurality of row electrodes, the switch control repeatedly applies the video input signal to the plurality of column electrodes and the structure repeatedly sets the plurality of column electrodes to the substantially constant voltage prior to the processor activating the subsequent row electrode, wherein the controller, the switch control and the structure are contained in a liquid crystal on silicon imager.

13. The system according to claim 12, wherein the controller is further programmed to activate at least a portion of the row electrodes sequentially.

14. The system according to claim 12, wherein the controller is further programmed to activate at least a portion of the row electrodes non-sequentially.

15. The system according to claim 10, further comprising an imager having active display lines, wherein the controller is further programmed to activate a row electrode associated with one of the active display lines.

16. The system according to claim 10, wherein the structure further comprises:

a memory for storing the video input signal; and

a multiplexer,

wherein the controller is further programmed to activate the subsequent row electrode once the plurality of column electrodes are set to the substantially constant voltage, wherein the multiplexer feeds the video input signal from the memory to the switch control for selective application of the video input signal to the plurality of column electrodes.

17. The system according to claim 16, further comprising an imager having display lines, wherein at least a portion of the display lines are hidden display lines, wherein the controller is further programmed to activate a subsequent row electrode associated with one of the hidden display lines such that a substantially constant brightness associated with the substantially constant voltage can be displayed on the hidden display line.

18. The system according to claim 10, wherein the structure further comprises at least one switch connected to a terminal and a common voltage source storing the substantially constant voltage, wherein, prior to activating the subsequent row electrode, the controller is further programmed to apply a pulse to the terminal, wherein the pulse activates the switch, wherein the common voltage source sets the plurality of column electrodes to the substantially constant voltage through the at least one switch.