Strain-based sensing of mirror position

Patent metadata

Field	Value
Publication number	US-2015241196-A1
Application number	US-201414552500-A
Country	US
Kind code	A1
Filing date	Nov 25, 2014
Priority date	Feb 26, 2014
Publication date	Aug 27, 2015
Grant date	—

Abstract

Mechanical apparatus includes a base, a moving element, and a hinge, having a first end attached to the moving element. A supporting structure is attached to the base and to the second end of the hinge and has at least a component perpendicular to the hinge so as to translate rotation of the moving element about the hinge into elongation of the component, whereby the moving element rotates about the hinge relative to the base while the supporting structure is deformed as a result of the rotation of the moving element about the hinge. A strain-based rotation sensor is associated with the supporting structure and is configured to provide a signal indicative of the rotation of the moving element responsively to a strain induced due to deformation of the supporting structure as the result of the rotation of the moving element.

First claim

1 . Mechanical apparatus, comprising:
a base; a moving element; a hinge, having a first end attached to the moving element and having a second end; a supporting structure, which is attached to the base and to which the second end of the hinge is attached and which has at least a component perpendicular to the hinge so as to translate rotation of the moving element about the hinge into elongation of the component, whereby the moving element rotates about the hinge relative to the base while the supporting structure is deformed as a result of the rotation of the moving element about the hinge; and a strain-based rotation sensor, which is associated with the supporting structure and is configured to provide a signal indicative of the rotation of the moving element responsively to a strain induced due to deformation of the supporting structure as the result of the rotation of the moving element.

2 . The apparatus according to claim 1 , wherein the component of the supporting structure that is perpendicular to the hinge comprises a beam, having ends that are attached to the base.

3 . The apparatus according to claim 1 , wherein at least the base, supporting structure, moving element and hinge are formed from a semiconductor wafer in a MEMS process, and the strain-based rotation sensor is formed on the semiconductor wafer as a part of the MEMS process.

4 . The apparatus according to claim 3 , wherein the strain-based rotation sensor comprises a piezoresistive sensor, which is formed by doping the semiconductor material in the supporting structure.

5 . The apparatus according to claim 3 , wherein the strain-based rotation sensor comprises a metallic strain sensor, comprising a metal trace deposited on the supporting structure.

6 . The apparatus according to claim 1 , wherein the moving element comprises a scanning mirror, and the base comprises a gimbal.

7 . The apparatus according to claim 1 , wherein the rotation sensor has a resistance that varies responsively to the strain in the supporting structure, and wherein the apparatus comprises a sensing circuit, which is coupled to output an indication of an angle of the rotation of the moving element responsively to the varying resistance.

8 . The apparatus according to claim 7 , wherein the sensing circuit comprises a resistor bridge.

9 . The apparatus according to claim 7 , wherein the rotation sensor comprises a cruciform strain sensor having two pairs of mutually-perpendicular arms, and wherein the sensing circuit is coupled to respective ends of the arms in order to sense the angle of the rotation.

10 . The apparatus according to claim 1 , wherein the hinge is one of a pair of hinges, attached to opposite sides of the moving element, and the strain-based rotation sensor is one of a pair of rotation sensors that are associated with supporting structures to which the hinges are attached on the opposite sides of the moving element.

11 . A method for sensing, comprising:
mounting a moving element to rotate on a hinge relative to a base, such that a first end of the hinge is attached to the moving element; attaching a second end of the hinge to a supporting structure attached to the base, the supporting structure having at least a component perpendicular to the hinge so as to translate rotation of the moving element about the hinge into elongation of the component, whereby the moving element rotates about the hinge relative to the base while the supporting structure is deformed as a result of the rotation of the moving element about the hinge; and measuring the rotation of the moving element by sensing a strain in the supporting structure induced due to deformation of the supporting structure as the result of the rotation of the moving element.

12 . The method according to claim 11 , wherein the component of the supporting structure that is perpendicular to the hinge comprises a beam, having ends that are attached to the base.

13 . The method according to claim 11 , wherein at least the base, supporting structure, moving element and hinge are formed from a semiconductor wafer in a MEMS process, and wherein sensing the strain comprises forming a strain-based rotation sensor on the semiconductor wafer as a part of the MEMS process.

14 . The method according to claim 13 , wherein the strain-based rotation sensor comprises a piezoresistive sensor, which is formed by doping the semiconductor material in the supporting structure.

15 . The method according to claim 13 , wherein the strain-based rotation sensor comprises a metallic strain sensor, comprising a metal trace deposited on the supporting structure.

16 . The method according to claim 11 , wherein the moving element comprises a scanning mirror, and the base comprises a gimbal.

17 . The method according to claim 11 , wherein the rotation sensor has a resistance that varies responsively to the strain in the supporting structure, and wherein sensing the strain comprises measuring a signal that varies responsively to the varying resistance.

18 . The method according to claim 17 , wherein measuring the signal comprises coupling a strain sensor on the supporting structure to a resistor bridge.

19 . The method according to claim 17 , wherein the rotation sensor comprises a cruciform strain sensor having two pairs of mutually-perpendicular arms, and wherein the signal is measured between respective ends of the arms in order to sense the angle of the rotation.

20 . The method according to claim 11 , wherein the hinge is one of a pair of hinges, attached to opposite sides of the moving element, and wherein sensing the strain comprises receiving signals from a pair of rotation sensors that are associated with supporting structures to which the hinges are attached on the opposite sides of the moving element.

Assignees

• Apple Inc

Inventors

• Gerson Yuval

Classifications

• G01B7/18

  using change in resistance · CPC title

• B81B3/00

  Devices comprising flexible or deformable elements, e.g. comprising elastic tongues or membranes (B81B5/00 takes precedence) · CPC title

• G02B26/0833 Primary

  the reflecting element being a micromechanical device, e.g. a MEMS mirror, DMD (G02B26/0825 takes precedence; micromechanical devices in general B81B) · CPC title

• G02B26/101

  with both horizontal and vertical deflecting means, e.g. raster or XY scanners (colour television using laser beams scanning a display screen H04N9/3129) · CPC title

• G02B26/0858

  the reflecting means being moved or deformed by piezoelectric means · CPC title