INTERFEROMETRIC MODULATORS HAVING CHARGE PERSISTENCE

• US 20100079421A1
• Filed: 12/09/2009
• Published: 04/01/2010
• Est. Priority Date: 09/27/2004
• Status: Active Grant

• Current Assignee: Snaptrack Incorporated (Qualcomm, Inc.)
• Original Assignee: Qualcomm MEMS Technologies Incorporated (Qualcomm, Inc.)
• Inventors: Chui, Clarence
• Granted Patent: US 7,995,265 B2
• Time in Patent Office: Days
• US Class Current: 345/204
• CPC Class Codes: G02B 26/001 based on interference in an adjustable optical cavity interference filters G02B5/28; devices or arrangements using multiple reflections in spectrometry or monochromators G01J3/26

Abstract

An interferometric modulator is formed having a dielectric with charge persistence. The interferometric modulator is addressed by a method making advantageous use of the charge persistence property, wherein the interferometric modulator is pre-charged in such a way that the pre-charging is not observable to a viewer, and the actuation voltage threshold of the imod is significantly lowered. Subsequently the interferometric modulator may be actuated with a significantly lower actuation voltage, thereby saving power.

Claims

1. A display device configured to display an image based on image data, the display device comprising:

an array of display elements; and

a driving circuit configured to embed a charge in at least one of the display elements thereby shifting an actuation threshold to one of a plurality of functional differentiable actuation thresholds.

2. The display device of claim 1, wherein the driving circuit is further configured to actuate the at least one of the display elements to embed the charge.

3. The display device of claim 1, wherein the at least one of the display elements comprises:

a movable reflective layer; and

a dielectric layer coupled to an electrode, dielectric layer being configured to store the charge, wherein a cavity is formed between the movable reflective layer and the dielectric layer.

4. The display device of claim 3, wherein the driving circuit is configured to actuate the at least one of the display elements causing the movable reflective layer to contact the dielectric layer.

5. The display device of claim 4, wherein the driving circuit is configured to actuate the at least one of the display elements by applying an electrical potential between the electrode and the movable reflective layer, the electrical potential being greater than the actuation threshold.

6. The display device of claim 4, wherein the driving circuit is configured to embed the charge by actuating the at least one of the display elements.

7. The display device of claim 1, wherein the driving circuit is configured to remove the charge from the at least one of the display elements by applying an alternating current to the at least one of the display elements.

8. The display device of claim 1, wherein the driving circuit is configured to remove the charge from the at least one of the display elements by applying an electrical pulse to the at least one of the display elements.

9. A display device comprising:

means for transferring a charge to a dielectric of a display element during a pre-charge period without substantially altering a perceived appearance; and

means for applying a first electrical potential difference to the display element during a period sufficient to actuate the display element and alter the perceived appearance.

10. The display device of claim 9, wherein the transferring means is further configured to repeat the act of transferring charge before the applying means applies the first electrical potential difference.

11. The display device of claim 9, further comprising means for applying a second electrical potential difference to the display element such that a movable layer of the display element contacts the dielectric and substantially removes the transferred charge therefrom.

12. The display device of claim 9, wherein said first electrical potential difference comprises a first polarity, and wherein the transferring means is further configured to apply a second electrical potential difference of a second polarity that is opposite the first polarity.

13. The display device of claim 9, wherein the applying means is configured to apply the first electrical potential difference by applying said first electrical potential difference for at least ten milliseconds.