Electrostatically actuated oscillating structure with oscillation starting phase control, and manufacturing and driving method thereof

Patent metadata

Field	Value
Publication number	US-2018157030-A1
Application number	US-201815887557-A
Country	US
Kind code	A1
Filing date	Feb 2, 2018
Priority date	Dec 12, 2013
Publication date	Jun 7, 2018
Grant date	—

Abstract

An electrostatically actuated oscillating structure includes a first stator subregion, a second stator subregion, a first rotor subregion and a second rotor subregion. Torsional elastic elements mounted to the first and second rotor subregions define an axis of rotation. A mobile element is coupled to the torsional elastic elements. The stator subregions are electrostatically coupled to respective regions of actuation on the mobile element. The stator subregions exhibit an element of structural asymmetry such that the electrostatic coupling surface between the first stator subregion and the first actuation region differs from the electrostatic coupling surface between the second stator subregion and the second actuation region.

First claim

What is claimed is:

1 . A MEMS projective system, comprising:
an oscillating structure; and a reflecting element, mechanically coupled to a mobile element of the oscillating structure, configured to reflect a light beam; wherein the oscillating structure comprises:
a first stator subregion,
a second stator subregion,
a first rotor subregion,
a second rotor subregion,
wherein the first and second rotor subregions are coupled by torsional elastic elements to the mobile element rotatable about an axis of rotation;
wherein the first and second stator subregions are electrostatically coupled to respective first and second regions of actuation of the mobile element,
wherein the first and second regions of actuation of the mobile element include a respective plurality of first and second elongated elements, which extend in cantilever fashion towards the first and second stator subregions, respectively, the first and second stator subregions including a respective plurality of third and fourth elongated elements comb-fingered to the first and second elongated elements, respectively, and
wherein one of the first and second stator subregions includes at least an element of structural asymmetry in the form of a protuberance of increased thickness extending, at least in part, on the third elongated elements in a direction perpendicular to an upper surface of the first and second stator subregions such that a surface available for electrostatic coupling between the third elongated elements and the first elongated elements is greater than the surface available for the electrostatic coupling between the fourth elongated elements and the second elongated elements.

2 . The system according to claim 1 , further comprising:
a light source actuated for generating a beam of light incident on said reflecting element; and an image-generation module, operatively coupled to said oscillating structure, for generating part of an image associated to the light beam reflected by said reflecting element.

3 . An apparatus, comprising:
a mobile element supported on opposed first and second ends for oscillation about an axis of rotation, wherein the mobile element further includes: a first region of electrostatic coupling including a plurality of first elongated elements disposed on a first side of the mobile element; a second region of electrostatic coupling including a plurality of second elongated elements disposed on a second side of the mobile element diametrically opposite the first region; a stator body including:
a third region of electrostatic coupling including a plurality of third elongated elements, the first elongated elements comb-fingered to the third elongated elements; and
a fourth region of electrostatic coupling including a plurality of fourth elongated elements, the second elongated elements comb-fingered with the fourth elongated elements;
wherein the third region is structurally asymmetric relative to the fourth region because the third region includes a protuberance of increased thickness extending, at least in part, on the third elongated elements in a direction perpendicular to an upper surface of the stator body;
wherein a first area of electrostatic coupling is formed by the adjacent first and third regions of electrostatic coupling; and
wherein a second area of electrostatic coupling is formed by the adjacent second and fourth regions of electrostatic coupling, the first area being greater than the second area because of the protuberance.

4 . A MEMS projective system, comprising:
an oscillating structure; and a reflecting element, mechanically coupled to a mobile element of the oscillating structure, configured to reflect a light beam; wherein the oscillating structure comprises:
a first stator subregion,
a second stator subregion,
a first rotor subregion,
a second rotor subregion,
wherein the first and second rotor subregions are coupled by torsional elastic elements to a mobile element rotatable about an axis of rotation;
wherein the first and second stator subregions are electrostatically coupled to respective first and second regions of actuation of the mobile element,
wherein one of the first and second stator subregions includes at least an element of structural asymmetry such that the surface available for electrostatic coupling between the first stator subregion and the first actuation region is greater than the surface available for the electrostatic coupling between the second stator subregion and the second actuation region.

5 . The system according to claim 4 , further comprising:
a light source actuated for generating a beam of light incident on said reflecting element; and an image-generation module, operatively coupled to said oscillating structure, for generating part of an image associated to the light beam reflected by said reflecting element.

6 . An apparatus, comprising:
a mobile element supported on opposed first and second ends for oscillation about an axis of rotation, wherein the mobile element further includes: a first region of electrostatic coupling on a first side of the mobile element; a second region of electrostatic coupling on a second side of the mobile element diametrically opposite the first region; a stator body including:
a third region of electrostatic coupled positioned adjacent the first region of electrostatic coupling; and
a fourth region of electrostatic coupling positioned adjacent the second region of electrostatic coupling;
wherein a first area of electrostatic coupling is formed by the adjacent first and third regions of electrostatic coupling;
wherein a second area of electrostatic coupling is formed by the adjacent second and fourth regions of electrostatic coupling; and
wherein the third region is structurally asymmetric relative to the fourth region such that the first and second areas of electrostatic coupling are not equal.

7 . The apparatus of claim 6 , wherein the third region includes a protuberance of increased thickness in a direction perpendicular to an upper surface of the stator body.

8 . The apparatus of claim 6 , wherein the third region includes a recess of decreased thickness in a direction perpendicular to an upper surface of the stator body.

Assignees

• St Microelectronics Srl
• St Microelectronics Int Nv

Inventors

• Vigna Benedetto
• Ferrera Marco
• Costantini Sonia
• Salina Marco

Classifications

• B81C1/00198

  comprising elements which are movable in relation to each other, e.g. comprising slidable or rotatable elements · CPC title

• H04N9/3129

  scanning a light beam on the display screen (scanning a light beam on a screen in displays other than projection devices G09G3/02; scanning systems in general G02B26/10; projectors using laser light sources in general H04N9/3161) · CPC title

• H04N9/3135

  Driving therefor · CPC title

• B81B3/0045

  Improve properties related to angular swinging, e.g. control resonance frequency · CPC title

• G02B26/0841 Primary

  the reflecting element being moved or deformed by electrostatic means · CPC title