Electrostatic microactuator and method for use thereof

• US 5,998,906 A
• Filed: 08/17/1998
• Issued: 12/07/1999
• Est. Priority Date: 01/13/1998
• Status: Expired due to Term

• Current Assignee: Coherent Inc (Coherent Corp.)
• Original Assignee: Seagate Technology plc (Seagate Technology Holdings Plc)
• Inventors: Jerman, John H., Grade, John D., Drake, Joseph D.
• Primary Examiner(s): Ramirez, Nestor
• Assistant Examiner(s): Jones, Judson H.
• Application Number:
  US09/135,158
• Time in Patent Office: 477 Days
• Field of Search: 310/309, 361/283.3, 318/116
• US Class Current: 310/309
• 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 6/3518 the reflective optical element being an intrinsic part of a MEMS device, i.e. fabricated together with the MEMS device MEMS devices in general B81B; manufacture of MEM devices in general B81C; micromechanical devices controlling the direction of light G02B26/0833
• CPC Class Codes: G02B 6/3548 1xN switch, i.e. one input and a selectable single output of N possible outputs
• CPC Class Codes: G02B 6/357 Electrostatic force electrostatic forces controlling reflecting elements in general G02B26/0841
• CPC Class Codes: G02B 6/358 Latching of the moving element, i.e. maintaining or holding the moving element in place once operation has been performed; includes a mechanically bistable system
• 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 6/4216 incorporating polarisation-maintaining fibres polarisation-maintaining fibres per se G02B6/105
• CPC Class Codes: G11B 7/1384 Fibre optics
• CPC Class Codes: H02N 1/008 Laterally driven motors, e.g. of the comb-drive type

Abstract

An electrostatic microactuator comprising a substrate and at least one comb drive assembly having first and second comb drive members. Each of the first and second comb drive members is provided with comb drive fingers. The first comb drive member is mounted on the substrate. The at least one comb drive assembly is disposed between the first and second spaced-apart, beam-like spring members. The second comb drive member overlies the substrate. Each of the first and second beam-like members have a first end portion secured to the substrate and a second end portion secured to the second comb drive member for suspending the second comb drive member over the substrate. The second comb drive member is movable between a first position in which the comb drive fingers of the first and second comb drive members are spaced apart and a second position in which the comb drive fingers of the first and second comb drive members are interdigitated.

Claims

1. An electrostatic microactuator comprising a substrate, at least one comb drive assembly having first and second comb drive members, each of the first and second comb drive members being provided with comb drive fingers, the first comb drive member being mounted on the substrate, first and second spaced-apart, beam-like spring members, the at least one comb drive assembly being disposed between the first and second beam-like spring members, the second comb drive member overlying the substrate, each of the first and second beam-like members having a first end portion secured to the substrate and a second end portion secured to the second comb drive member for suspending the second comb drive member over the substrate, the second comb drive member being movable between a first position in which the comb drive fingers of the first and second comb drive members are spaced apart and a second position in which the comb drive fingers of the first and second comb drive members are interdigitated.

2. An electrostatic microactuator as in claim 1 wherein the first and second beam-like spring members each have a stiffness in a direction perpendicular to the direction of movement of the second comb drive member, each of the first and second beam-like spring members being movable between a first position in which the beam-like spring member is in a nonlinear configuration and occurring when the second comb drive member is in the first position and a second position in which the beam-like spring member is in a linear configuration extending perpendicularly of the direction of movement and occurring when the second comb drive member is in the second position whereby the stiffness of the first and second beam-like spring members in a direction perpendicular to the direction of movement is maximized when the second comb drive member is in the second position.

3. An electrostatic microactuator as in claim 1 wherein the second comb drive member is secured to the substrate solely by the first and second beam-like spring members.

4. An electrostatic microactuator as in claim 1 wherein the second comb drive member is movable under the force of the first and second beam-like spring members from the second position to the first position, the microactuator being free of additional comb drive assemblies having first and second comb drive members with respective comb drive fingers in which the second comb drive member of said additional comb drive assembly is movable to a position in which said comb drive fingers of the additional comb drive assembly are interdigitated when the comb drive fingers of the first-named comb drive assembly are spaced apart.

5. An electrostatic microactuator as in claim 1 further comprising first and second electrostatic clamping electrodes extending perpendicularly of the direction of movement of the second comb drive member, the first and second clamping electrodes being movable between a first position in which the clamping electrodes are spaced apart and occurring when the second comb drive member is in the second position and a second position in which the clamping electrodes are in close proximity to each other and occurring when the second comb drive member is in the first position whereby the clamping electrodes facilitate retention of the second comb drive member in the first position when a voltage potential is applied between the clamping electrodes disposed in the second position in close proximity to each other.

6. An electrostatic microactuator as in claim 1 further comprising an additional comb drive assembly disposed between the first and second beam-like spring members and having first and second comb drive members, each of the first and second comb drive members of the additional comb drive assembly being provided with comb drive fingers, the first comb drive member of the additional comb drive assembly being mounted on the substrate, the second comb drive member of the additional comb drive assembly overlying the substrate and being suspended over the substrate by the first and second beam-like spring members, the second comb drive member of the additional comb drive assembly being movable between a first position in which the comb drive fingers of the first and second comb drive members of the additional comb drive assembly are spaced apart and a second position in which the comb drive fingers of the first and second comb drive members of the additional comb drive assembly are interdigitated, the second comb drive member of the additional comb drive assembly being in the second position when the second comb drive member of the first-named comb drive assembly is in the first position.

7. An electrostatic microactuator as in claim 6 further comprising first and second sets of electrostatic clamping electrodes extending perpendicularly of the direction of movement of the second comb drive members, each of the first and second sets of clamping electrodes having first and second clamping electrodes movable between a first position in which the clamping electrodes are spaced apart and a second position in which the clamping electrodes are in close proximity to each other, the clamping electrodes of the first set being in close proximity to each other when the second comb drive member of the first-named comb drive assembly is in the first position and the clamping electrodes of the second set being in close proximity to each other when the second comb drive member of the additional comb drive assembly is in the first position whereby the clamping electrodes of each set facilitate retention of the second comb drive members in their respective first positions when a voltage potential is applied between said clamping electrodes in the second position in close proximity to each other.

8. An electrostatic microactuator as in claim 1 further comprising a micromotor which is normally closed for locking the second drive member in its first and second positions.

9. An electrostatic microactuator as in claim 1 wherein the comb drive fingers of each of the first and second comb drive members have proximal and distal end portions, each of the proximal end portions having a width and each of the distal end portions having a width which is less than the width of the respective proximal end portion.

10. An electrostatic microactuator as in claim 1 wherein the comb drive fingers of at least one of the first and second comb drive members have varying lengths.

11. An electrostatic microactuator as in claim 1 further comprising travel stop means for limiting the movement of the second comb drive member to the second position whereby the travel stop means facilitates repeatability in the operation of microactuator.

12. An electrostatic microactuator as in claim 11 further comprising a controller and lead means for electrically connecting the travel stop means to the controller whereby the travel stop means permits the controller to monitor when the second comb drive member is in the second position.

13. An electrostatic microactuator as in claim 1 wherein the comb drive fingers of the second comb drive member are movable in a half-stroke from a first position in which the comb drive fingers of the first and second comb drive members are spaced apart to a second position in which said comb drive fingers are partially interdigitated and to a third position in which said comb drive fingers are fully interdigitated, a controller including means for providing a voltage potential between the first and second comb drive members during only a portion of the half-stroke for urging the comb drive fingers of the second comb drive member to the third position.

14. An electrostatic microactuator as in claim 13 wherein the controller includes means for providing a voltage potential between the first and second comb drive members while said comb drive fingers are partially engaged but before said comb drive fingers are fully engaged.

15. An electrostatic actuator as in claim 1 further comprising a mirror and attachment means for coupling the mirror to the at least one comb drive assembly, the attachment means including a bracket member provided with a recess therein, the mirror having a peg portion provided thereon for disposition in the recess to facilitate alignment of the mirror on the bracket member.

16. An electrostatic actuator as in claim 1 further comprising a mirror and attachment means for coupling the mirror to the at least one comb drive assembly, the attachment means including a bracket member provided with a receptacle for receiving the mirror, adhesive means for securing the mirror within the receptacle and a retention member removably mounted on the substrate for retaining the mirror in the receptacle during securement.

17. A method for operating a comb drive assembly having first and second comb drive members with respective comb drive fingers in which the second comb drive member is movable relative to the first comb drive member between a first position in which the comb drive fingers of the first and second comb drive members are spaced apart and a second position in which the comb drive fingers of the first and second comb drive members are interdigitated comprising the steps of oscillating the second comb drive member at resonance to move the second comb drive member to the second position and retaining the second comb drive in the second position.

18. A method as in claim 17 wherein the retaining step includes retaining the second comb drive member in the second position by means of an electrostatic force.

19. A method as in claim 17 wherein the retaining step includes retaining the second comb drive member in the second position by means of a mechanical force.

20. A method as in claim 17 further comprising the step of releasing the second comb drive member from the second position to permit the second comb drive member to move to the first position.

21. An electrostatic microactuator comprising a substrate, at least one comb drive assembly having first and second comb drive members, each of the first and second comb drive members being provided with comb drive fingers, the first comb drive member being mounted on the substrate and the second comb drive member overlying the substrate, and at least one beam-like spring member having a first end portion secured to the substrate and a second end portion secured to the second comb drive member, the second comb drive member being movable in a direction between a first position in which the comb drive fingers of the first and second comb drive members are not substantially fully interdigitated and a second position in which the comb drive fingers of the first and second comb drive members are substantially fully interdigitated, the at least one beam-like spring member having a stiffness in a direction perpendicular to the direction of movement of the second comb drive member and being movable between a first position in which the at least one beam-like spring member is in a nonlinear configuration and occurring when the second comb drive member is in the first position and a second position in which the at least one beam-like spring member is in a linear configuration extending perpendicular to the direction of movement and occurring when the second comb drive member is in the second position whereby the stiffness of the at least one beam-like spring member in a direction perpendicular to the direction of movement increases as the second comb drive member moves from its first position to its second position.

22. An electrostatic microactuator as in claim 21 wherein the second comb drive member is movable in a direction between a first position in which the comb drive fingers of the first and second comb drive members are spaced apart and a second position in which the comb drive fingers of the first and second comb drive members are substantially fully interdigitated.

23. An electrostatic microactuator as in claim 21 further comprising an additional beam-like spring member having a first end portion secured to the substrate and a second end portion secured to the second comb drive member, the additional beam like spring member having a stiffness in a direction perpendicular to the direction of movement of the second comb drive member and being movable between a first position in which the additional beam-like spring member is in a nonlinear configuration and occurring when the second comb drive member is in the first position and a second position in which the additional beam-like spring member is in a linear configuration extending perpendicular to the direction of movement and occurring when the second comb drive member is in the second position.

24. An electrostatic microactuator as in claim 21 further comprising first and second electrostatic clamping electrodes extending perpendicularly of the direction of movement of the second comb drive member, the first and second clamping electrodes being movable between a first position in which the clamping electrodes are spaced apart and occurring when the second comb drive member is in the second position and a second position in which the clamping electrodes are in close proximity to each other and occurring when the second comb drive member is in the first position whereby the clamping electrodes facilitate retention of the second comb drive member in the first position when a voltage potential is applied between the clamping electrodes disposed in the second position in close proximity to each other.

25. An electrostatic microactuator comprising a substrate, at least one comb drive assembly having first and second comb drive members, each of the first and second comb drive members being provided with comb drive fingers, the first comb drive member being mounted on the substrate and the second comb drive member overlying the substrate and being movable in a direction between a first position in which the comb drive fingers of the first and second comb drive members are not substantially fully interdigitated and a second position in which the comb drive fingers of the first and second comb drive members are substantially fully interdigitated, and spring means having a first end portion secured to the substrate and a second end portion secured to the second comb drive member for providing stiffness in a direction perpendicular to the direction of movement of the second comb drive member which increases as the second comb drive member moves from its first position to its second position.

26. An electrostatic microactuator as in claim 25 further comprising means apart from the first and second comb drive members for electrostatically securing the second comb drive member in the first position.

27. An electrostatic microactuator as in claim 26 wherein the means for electrostatically securing the second comb drive member in the first position includes first and second clamping electrodes movable between a first position in which the clamping electrodes are spaced apart and occurring when the second comb drive member is in the second position and a second position in which the clamping electrodes are in close proximity to each other and occurring when the second comb drive member is in the first position.