Two-dimensional micro-mirror array enhancements

• US 6,744,550 B2
• Filed: 05/28/2002
• Issued: 06/01/2004
• Est. Priority Date: 11/16/1999
• Status: Expired due to Fees

• Current Assignee: RPX Clearinghouse LLC (RPX Corporation)
• Original Assignee: Xros, Inc. (Nortel Networks Corporation)
• Inventors: Ang, Jane, Malhotra, Arun, Bajikar, Sateesh S., Calmes, Sam, Foster, Jack D., Schuman, Marc R., Slater, Timothy G., Neukermans, Armand P., Green, John, Hurst, Jerry
• Primary Examiner(s): Sugarman, Scott J.
• Assistant Examiner(s): Dinh, Jack
• Application Number:
  US10/157,354
• Publication Number:
  US 20030076576A1
• Time in Patent Office: 735 Days
• Field of Search: 359/290, 359/291, 359/295, 359/223, 359/224, 359/298, 359/348, 359/203, 359/205, 735/040.2, 735/041.2
• US Class Current: 359/291
• CPC Class Codes: G02B 26/0833 the reflecting element being a micromechanical device, e.g. a MEMS mirror, DMD G02B26/0825 takes precedence; micromechanical devices in general B81B
• CPC Class Codes: G02B 26/0841 the reflecting element being moved or deformed by electrostatic means
• CPC Class Codes: G02B 26/085 the reflecting means being moved or deformed by electromagnetic means
• CPC Class Codes: G02B 6/262 Optical details of coupling light into, or out of, or between fibre ends, e.g. special fibre end shapes or associated optical elements
• CPC Class Codes: G02B 6/32 having lens focusing means positioned between opposed fibre ends with lens being an integral part of the single fibre end G02B6/262
• CPC Class Codes: G02B 6/3512 the optical element being reflective, e.g. mirror
• CPC Class Codes: G02B 6/356 in an optical cross-connect device, e.g. routing and switching aspects of interconnecting different paths propagating different wavelengths to (re)configure the various input and output links switching polarized beams G02B6/3594; power equalizers G02B6/356 and G02B6/3594; path selecting means H04Q11/0001
• CPC Class Codes: G02B 6/357 Electrostatic force electrostatic forces controlling reflecting elements in general G02B26/0841
• CPC Class Codes: G02B 6/3584 constructional details of an associated actuator having a MEMS construction, i.e. constructed using semiconductor technology such as etching MEMS per se B81B, B81C
• CPC Class Codes: G02B 6/359 of the position of the moving element itself during switching, i.e. without monitoring the switched beams
• CPC Class Codes: G02B 6/4249 comprising arrays of active devices and fibres

Abstract

A micro-mirror strip assembly having a plurality of two-dimensional micro-mirror structures with improved deflection and other characteristics is presented. In the micro-mirror structures, electrodes for electrostatic deflection are disposed on conical or quasi-conical entities that are machined, attached or molded into a substrate. The electrodes are quartered approximately parallel to or offset by 45 degrees from rotational axes to form quadrants. Torsion sensors are provided along the axes of rotation to control deflection of the quadrant deflection electrodes.

Claims

1. A structure comprising:

a reference member having a raised portion thereon;

a mirror suspended above the raised portion; and

driving devices disposed on the raised portion to impart rotational motion to the mirror in two axes of direction.

2. The structure of claim 1, wherein the raised portion has a conical shape.

3. The structure of claim 1, wherein the raised portion has a quasi-conical shape.

4. The structure of claim 1m wherein the raised portion has a polygonal shape.

5. The structure of claim 1, wherein the mirror is coupled to the reference member by torsion hinges, and wherein the torsion hinges each comprise multiple, parallel vertical slots therein, the slots serving to partition the torsion hinge into narrow sections having a lower torque constant than the torsion hinge without such slots.

6. The structure of claim 5, wherein the narrow sections and vertical slots serve to maximize lateral and vertical stiffness while minimizing the torsional spring constant of the torsion hinges.

7. The structure of claim 5, wherein the torsion hinges include a torsional sensor.

8. The structure of claim 5, wherein the slots are etched through the full thickness of the hinge.

9. The structure of claim 1, further comprising:

a mirror frame, the mirror being coupled to the mirror frame by a first pair of torsion hinges located along a first, inner rotational axis and the mirror frame being coupled to the reference member by a second pair of torsion hinges located along a second outer rotational axis; and

wherein torsion hinges in each pair include a torsion sensor coupled to a torsion sensor select circuit, the torsion sensor select circuit for selecting one of the torsion sensors as active.

10. The structure of claim 9, wherein each of the torsion sensors has an input and an output and wherein the torsion select circuit includes select lines for selectively coupling the input of one of the sensors to a current source and the output to an instrumentation amplifier.

11. The structure of claim 9, wherein the driving devices are electrodes that are quartered to form electrodes in four corresponding quadrants of the raised portion.

12. The structure of claim 11, wherein the quartering is generally parallel to a first, inner rotational axis and the second, outer rotational axis.

13. The structure of claim 11, wherein the quartering is offset from the first, inner rotational axis and the second, outer rotational axis by approximately 45 degrees.

14. The structure of claim 11, further comprising a servo control unit, comprising:

an amplifier circuit for driving a corresponding one of the electrodes, the amplifier circuit receiving as inputs a biasing voltage and feedback signals from the torsion sensors, the inputs being weighted for each electrode and the feedback signals being inverted as necessary according to direction of rotation.

15. The structure of claim 9, wherein the torsion hinges, the mirror and the torsion sensors are fabricated to be of different thicknesses.

16. The structure of claim 9, wherein the torsional sensors each comprise a shielded sensor structure including a sensor implant layer and a shield applied over the sensor implant layer to stabilize sensor output and eliminate light sensitivity of such torsional sensor.

17. The structure of claim 1, wherein the reference member is a silicon substrate and the mirror is defined in a SOI top layer.

18. The structure of claim 17, further including an intermediate silicon layer disposed between the silicon substrate and the SOI top layer.

19. The structure of claim 17, further comprising sense amplifiers and currents sources embedded in the SOI top layer.

20. The structure of claim 17, further comprising sense amplifiers and currents sources embedded in the silicon substrate.

21. The structure of claim 1, wherein the mirror is coupled to the reference member by torsion hinges and the torsion hinges each comprise a torsion hinge having a steep return to the mirror to minimize bending on the mirror frame.

22. The structure of claim 1, wherein the mirror is coupled to the reference member by torsion hinges and the torsion hinges each comprise a folded torsion hinge having flexible members coupled by vertically stiff inner and outer members, the inner and outer members being tied together by a torsionally flexible, vertically stiff torsional element.

23. The structure of claim 1, wherein the mirror is coupled to the reference member by torsion hinges and wherein the torsion hinges each comprise a bending hinge including connection members which are connected by bands that are connected by end portions, wherein corresponding ones of the end portions in each band are connected by a torsion element that enables the end portions to rotate with respect to each other while being held together vertically.

24. The structure of claim 1, wherein the driving devices are electrodes and the electrodes are made of a highly resistive material.

25. The structure of claim 24, wherein the highly resistive material is polysilicon.

26. The structure of claim 1, wherein the driving devices are electrodes and the electrodes are coated with an insulating material in locations of the electrodes that may be in contact with the mirror.