Spatial light modulator and method

• US 5,061,049 A
• Filed: 09/13/1990
• Issued: 10/29/1991
• Est. Priority Date: 08/31/1984
• Status: Expired due to Term

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Hornbeck, Larry J.
• Primary Examiner(s): Moskowitz, Nelson
• Application Number:
  US07/582,804
• Time in Patent Office: 411 Days
• Field of Search: 350/6.9
• US Class Current: 359/224.1
• CPC Class Codes: G02B 26/02 for controlling the intensity of light G02B26/004 takes precedence
• CPC Class Codes: G02B 26/08 for controlling the direction of light in light guides G02B6/35
• CPC Class Codes: G02B 26/0841 the reflecting element being moved or deformed by electrostatic means
• CPC Class Codes: G02B 6/12004 Combinations of two or more optical elements
• CPC Class Codes: G02B 7/1827 Motorised alignment
• CPC Class Codes: G03F 7/70291 Addressable masks, e.g. spatial light modulators [SLMs], digital micro-mirror devices [DMDs] or liquid crystal display [LCD] patterning devices
• CPC Class Codes: G06K 15/1252 using an array of light modulators, e.g. a linear array
• CPC Class Codes: H04N 5/7458 the modulator being an array of deformable mirrors, e.g. digital micromirror device [DMD]

Abstract

An electrostatically deflectable beam spatial light modulator with the beams (30), address electrodes (42, 46), and landing electrodes (40, 41) to provide soft-landing of the beams on the landing electrodes (40, 41) which gives uniform large-angle deflection plus high reliability.

Claims

1. A spatial light modulator, comprising:

(a) a plurality of pixels, each of said pixels including a deflectable beam, an address electrode adjacent said beam, and a landing electrode adjacent said beam;

(b) wherein a voltage applied between said beam and said address electrode deflects said beam toward said address electrode, and said landing electrode is located to contact said beam deflected toward said address electrode and prevent said deflected beam from contacting said address electrode.

2. The spatial light modulator of claim 1, wherein:

(a) said deflectable beams are formed in a reflecting layer supported away from said address electrodes and landing electrodes, said deflectable beams connected to said reflecting layer by hinges formed in said reflecting layer.

3. The spatial light modulator of claim 2, wherein:

(a) said reflecting layer is supported away from said address electrodes and landing electrodes by a spacer layer with wells between said deflectable beams and said electrodes.

4. The spatial light modulator of claim 3, wherein:

(a) each of said deflectable beams is connected to said reflecting layer by two torsion hinges; and

(b) each of said pixels has two address electrodes and two landing electrodes.

5. The spatial light modulator of claim 4, wherein:

(a) said deflectable beams and landing electrodes are connected to a voltage source.

6. The spatial light modulator of claim 2, wherein:

(a) said reflecting layer is supported away from said address electrodes and landing electrodes by a plurality of posts.

7. The spatial light modulator of claim 6, wherein:

(a) each of said deflectable beams is connected to said reflecting layer by two torsion hinges; and

(b) each of said pixels has two address electrodes and two landing electrodes.

8. The spatial light modulator of claim 7, wherein:

(a) said deflectable beams and landing electrodes are connected to a voltage source.

9. A spatial light modulator, comprising:

(a) a plurality of pixels formed in a layered structure;

(b) said layered structure including an insulated substrate, a spacer layer on said substrate, a conductive reflecting layer on said spacer layer, and a plurality of addressing and landing electrodes;

(c) each of said pixels including

i. a deflectable element formed in said reflecting layer and connected to the remainder of said reflecting layer by at least one hinge formed from said reflecting layer,

ii. a well formed in said spacer layer and extending from said deflectable element to said substrate,

iii. a first addressing electrode on said substrate at the bottom of said well and located to deflect said deflectable element by electrostatic attraction, and

iv. a first landing electrode on said substrate at the bottom of said well, said first landing electrode located both to contact said deflectable element when said deflectable element is deflected by attraction by said first addressing electrode to said substrate and to prevent said deflectable element from contacting said addressing electrode.

10. The spatial light modulator of claim 9, wherein:

(a) said deflectable element and said first landing electrode are electrically connected.

11. The spatial light modulator of claim 9, wherein:

(a) said deflectable element is connected to the remainder of said reflecting layer by two hinges formed from said reflecting layer, said deflectable element deflectable by rotation about the axis defined by said two hinges.

12. The spatial light modulator of claim 11, wherein said each pixel further includes:

(a) a second addressing electrode on said substrate at the bottom of said well and located to deflect said element by electrostatic attraction in a direction of rotation opposite the direction of rotation due to attraction by said first addressing electrode; and

(b) a second landing electrode on said substrate at the bottom of said well, said second landing electrode located to contact said deflectable element when said deflectable element is deflected by attraction by said second addressing electrode to said substrate.

13. The spatial light modulator of claim 12, wherein said each pixel further includes:

(a) a voltage supply connected between said deflectable element plus said landing electrodes and said substrate.

14. The spatial light modulator of claim 9, wherein:

(a) said reflecting layer is made of first and second sublayers, each of said sublayers a metal; and

(b) said at least one hinge is formed from only said first sublayer.

15. A spatial light modulator, comprising:

(a) a plurality of pixels formed in a layered structure;

(b) said layered structure including a bottom layer, a plurality of electrodes on said bottom layer, a planarizing spacer layer on said electrodes and bottom layer, and a conductive reflecting layer on said spacer layer;

(c) each of said pixels including;

i. a deflectable element formed in said reflecting layer;

ii. first and second of said electrodes, said first and second electrodes both extending beneath said deflectable element, said first electrode an addressing electrode and said second electrode a landing electrode; and

iii. a well formed in said spacer layer, said well extending from said deflectable element to said first and second electrodes and of width greater than the width of said deflectable element.

16. The spatial light modulator of claim 15, wherein:

(a) said deflectable element is a portion of said reflecting layer connected to the remainder of said reflecting layer by two hinges formed from said reflecting layer.

17. The spatial light modulator of claim 16, wherein:

(a) said portion of said reflecting layer is of square shape and said hinges are located at diagonally opposite corners of said portion.

18. The spatial light modulator of claim 15, wherein:

(a) said well is characterized by a plasma etching of said spacer layer after said reflecting layer is on said spacer layer and said spacer layer is on said electrodes and said bottom layer and said deflectable element has been formed in said reflecting layer.

19. The spatial light modulator of claim 15, wherein said each pixel further includes:

(a) third and fourth of said electrodes extending beneath said deflectable element, said third electrode an addressing electrode and said fourth electrode a landing electrode.

20. A deflectable beam light modulator, comprising:

(a) an air gap capacitor with a first capacitor plate being a light-reflecting deflectable and conductive beam and a second capacitor plate being an addressing electrode; and

(b) a conductive landing electrode of a selected potential different from the potential of said addressing electrode located to stop the deflection of said beam at a predetermined position away from maid addressing electrode.

21. The light modulator of claim 20, wherein said:

(a) said beam is conductive; and

(b) said deflection stop is a conductive landing electrode has the same electrical potential as said beam.

22. The light modulator of claim 20, wherein:

(a) said beam is metal;

(b) said landing electrode is a metal landing electrode adjacent said addressing electrode; and

(c) said addressing electrode is metal.

23. The light modulator of claim 20, wherein:

(a) said landing electrode is insulated.

24. A deflectable beam light modulator, comprising:

(a) an air gap capacitor with a first capacitor plate being a light reflecting deflectable beam and a second capacitor plate being an addressing electrode; and

(b) an insulated landing electrode located to stop the deflection of said beam at a predetermined position away from said addressing electrode.

25. A deflectable beam light modulator, comprising:

(a) an air gap capacitor with a first capacitor plate being a light-reflecting deflectable beam having a deflection axis and a second capacitor plate being an addressing electrode; and

(b) a deflection stop located outwardly of said deflection axis and said addressing electrode, said deflection stop to stop the deflection of said beam when said beam comes in contact with said deflection stop at a predetermined position away from said addressing electrode.

26. The light modulator of claim 25, wherein:

(a) said beam is conductive; and

(b) said deflection stop is a conductive landing electrode at a selected electrical potential different from that of said addressing electrode.

27. The light modulator of claim 26, wherein:

(a) said beam is metal;

(b) said deflection stop is a metal landing electrode adjacent said addressing electrode; and

(c) said addressing electrode is metal.

28. The light modulator of claim 25, wherein:

(a) said deflection stop is an insulated landing electrode.