Electrophoretic Light Modulator

• US 20090201570A1
• Filed: 02/06/2009
• Published: 08/13/2009
• Est. Priority Date: 02/08/2008
• Status: Active Grant

• Current Assignee: Raytheon Company (Rtx Corporation)
• Original Assignee: Raytheon Company (Rtx Corporation)
• Inventors: Trent, Catherine, Frazier, Gary A.
• Granted Patent: US 8,130,441 B2
• Time in Patent Office: Days
• US Class Current: 359/296
• CPC Class Codes: G02F 1/167 by electrophoresis
• CPC Class Codes: G02F 1/1676 Electrodes
• CPC Class Codes: G02F 1/1677 Structural association of cells with optical devices, e.g. reflectors or illuminating devices
• CPC Class Codes: G02F 1/1685 Operation of cells; Circuit arrangements affecting the entire cell

Abstract

An electrophoretic light modulator includes a plurality of similarly charged particles comprising a first optical characteristic. The electrophoretic light modulator also includes at least one reflecting surface comprising a second optical characteristic different that the first optical characteristic. The electrophoretic light modulator further includes a pair of electrodes that create an electric field that causes the plurality of charged particles to obscure or expose the reflecting surface based on the polarity of the electric field.

Claims

1. An electrophoretic light modulator, comprising:

an optically transparent upper electrode through which light can pass;

a lower electrode;

an enclosed volume between the upper electrode and the lower electrode;

an electrophoretic fluid within the enclosed volume;

a voltage source coupled to the upper electrode and the lower electrode, the voltage source operable to apply a bias between the upper electrode and the lower electrode and further operable to switch between a first bias state and a second bias state;

a plurality of electrophoretic particles suspended in the electrophoretic fluid, the electrophoretic particles comprising a first optical characteristic and responsive to the bias applied between the upper electrode and the lower electrode; and

at least one reflecting surface comprising a second optical characteristic, the reflecting surface arranged so that when the first bias state is applied between the upper electrode and the lower electrode the plurality of electrophoretic particles obscure the reflecting surface from the light and when the second bias state is applied between the upper electrode and the lower electrode the plurality of electrophoretic particles expose the reflecting surface to the light.

2. The electrophoretic light modulator of claim 1, wherein the at least one reflecting surface comprises a perforated surface within the enclosed volume that is substantially parallel to the upper electrode through which light passes, wherein the perforations are sized based on an average size of the plurality of electrophoretic particles.

3. The electrophoretic light modulator of claim 1, wherein the at least one reflecting surface comprises a plurality of substantially coplanar reflecting surfaces, each reflecting surface coupled to the lower electrode via a post.

4. The electrophoretic light modulator of claim 1, further comprising a plurality of capsules filled with the electrophoretic fluid, each capsule comprising a subset of the plurality of electrophoretic particles.

5. The electrophoretic light modulator of claim 1, wherein the lower electrode comprises an electrode grid, the electrode grid comprising a plurality of intersecting electrodes that are substantially parallel with the upper electrode.

6. The electrophoretic light modulator of claim 1, wherein the first optical characteristic comprises an optically absorbent characteristic and the second optical characteristic comprises an optically reflective characteristic.

7. An electrophoretic light modulator, comprising:

a pair of electrodes comprising a space there between;

an electrophoretic fluid within the space between the pair of electrodes;

a plurality of electrically charged particles suspended in the electrophoretic fluid each having a first optical characteristic;

a voltage source coupled to the pair of electrodes and operable to;

generate a first bias attracting the charged particles towards a first electrode of the pair of electrodes; and

generate a second bias attracting the charged particles towards a second electrode of the pair of electrodes; and

at least one reflecting surface comprising a second optical characteristic, wherein the reflecting surface is obscured by the charged particles when the voltage source generates the first bias and the reflecting surface is exposed when the voltage source generates the second bias.

8. The electrophoretic light modulator of claim 7, wherein the at least one reflecting surface comprises a perforated surface within the enclosed volume that is substantially parallel to one of the electrodes of the pair of electrodes, wherein the perforations are sized based on an average size of the plurality of electrically charged particles.

9. The electrophoretic light modulator of claim 7, wherein the at least one reflecting surface comprises a plurality of substantially coplanar reflecting surfaces, each reflecting surface coupled to an electrode of the pair of electrodes via a post.

10. The electrophoretic light modulator of claim 7, further comprising a plurality of capsules filled with the electrophoretic fluid, each capsule comprising a subset of the plurality of charged particles.

11. The electrophoretic light modulator of claim 7, wherein one electrode of the pair of electrodes comprises an electrode grid, the electrode grid comprising a plurality of intersecting electrodes that are substantially parallel with the other electrode of the pair of electrodes.

12. The electrophoretic light modulator of claim 7, wherein the first optical characteristic comprises an optically absorbent characteristic and the second optical characteristic comprises an optically reflective characteristic.

13. An electrophoretic light modulator, comprising:

a plurality of similarly charged particles each having a first optical characteristic;

at least one reflecting surface comprising a second optical characteristic different that the first optical characteristic; and

a pair of electrodes that create an electric field that causes the plurality of charged particles to obscure or expose the reflecting surface based on the polarity of the electric field.

14. The electrophoretic light modulator of claim 13, wherein the at least one reflecting surface comprises a perforated surface situated between, and substantially parallel with, the pair of electrodes, wherein the perforations are sized based on an average size of the plurality of charged particles.

15. The electrophoretic light modulator of claim 13, wherein the at least one reflecting surface comprises a plurality of substantially coplanar reflecting surfaces situated between the pair of electrodes, each reflecting surface coupled to one of the electrodes of the pair of electrodes via a post.

16. The electrophoretic light modulator of claim 13, further comprising a plurality of capsules filled with an electrophoretic fluid, the electrophoretic fluid within each capsule suspending a subset of the plurality of charged particles.

17. The electrophoretic light modulator of claim 13, wherein one electrode of the pair of electrodes comprises an electrode grid, the electrode grid comprising a plurality of intersecting electrodes that are substantially parallel with the other electrode of the pair of electrodes.

18. The electrophoretic light modulator of claim 13, wherein the first optical characteristic comprises an optically absorbent characteristic and the second optical characteristic comprises an optically reflective characteristic.

19. A method of modulating light, comprising:

receiving light from a light source;

attracting a plurality of charged electrophoretic particles having a first optical characteristic towards a first electrode of two electrodes by applying a first bias between the two electrodes;

obscuring a reflecting surface having a second optical characteristic from the received light by attracting the charged electrophoretic particles to the first electrode, the charged electrophoretic particles;

attracting the plurality of charged electrophoretic particles towards a second electrode of the two electrodes by applying a second bias between the two electrodes; and

exposing the reflecting surface to the received light by attracting the particles to the second electrode.

20. The method of claim 19, further comprising switching between applying the first bias and the second bias.