Grating only optical microphone

Patent metadata

Field	Value
Publication number	US-2016007108-A1
Application number	US-201414325204-A
Country	US
Kind code	A1
Filing date	Jul 7, 2014
Priority date	Jul 7, 2014
Publication date	Jan 7, 2016
Grant date	—

Abstract

A micro-electro-mechanical system (MEMS) optical sensor including an enclosure having a top wall, a bottom wall and a sidewall connecting the top wall and the bottom wall. The sensor further including a compliant membrane positioned within the enclosure, which is configured to vibrate in response to an acoustic wave and having a grating formed therein. A reflector is formed directly on an inner surface of one of the bottom wall or the top wall of the enclosure. A light emitter is positioned within the enclosure along a side of the compliant membrane opposite the reflector, the light emitter is configured to transmit a laser light toward the grating and the reflector. A light detector is positioned along the side of the compliant membrane opposite the reflector, the light detector configured to detect an interference pattern of the laser light, which is indicative of an acoustic vibration of the compliant membrane.

First claim

What is claimed is:

1 . An optical microphone comprising:
an enclosure having a top wall, a bottom wall and a sidewall connecting the top wall and the bottom wall; a compliant membrane positioned within the enclosure, the compliant membrane configured to vibrate in response to an acoustic wave and having a grating formed therein; a reflector formed directly on an inner surface of one of the bottom wall or the top wall of the enclosure; a light emitter positioned within the enclosure along a side of the compliant membrane opposite the reflector, the light emitter configured to transmit a laser light toward the grating and the reflector; and a light detector positioned along the side of the compliant membrane opposite the reflector, the light detector configured to detect an interference pattern of the laser light after reflection from the reflector, wherein the interference pattern is indicative of an acoustic vibration of the compliant membrane.

2 . The optical microphone of claim 1 wherein the compliant membrane comprises a spring from which it is suspended within the enclosure.

3 . The optical microphone of claim 1 wherein the compliant membrane comprises 1) the grating formed within a rigid frame portion of the compliant membrane and 2) a compliant outer portion that is attached to a support member.

4 . The optical microphone of claim 1 wherein the reflector is a metal coated substrate having a top side facing the grating and a bottom side mounted directly to one of the top wall or the bottom wall.

5 . The optical microphone of claim 1 wherein the reflector is a metal coating applied to the inner surface.

6 . The optical microphone of claim 1 wherein the reflector is immovable relative to the compliant membrane.

7 . The optical microphone of claim 1 wherein the reflector is formed on the bottom wall and the enclosure further comprises an acoustic port formed through the top wall.

8 . A micro-electro-mechanical system (MEMS) optical sensor comprising:
a MEMS optical sensor enclosure having a wall upon which a reflector is positioned; a diaphragm positioned within the enclosure, the diaphragm having a grating, the grating spaced a distance above the reflector; a light emitter positioned above the diaphragm, the light emitter configured to transmit a laser light toward the grating and the reflector; and a light detector positioned above the diaphragm, the light detector configured to detect an interference pattern of the laser light after reflection from the reflector, wherein the interference pattern is indicative of an acoustic vibration of the diaphragm.

9 . The optical sensor of claim 8 further comprising:
a diaphragm support member extending from the wall toward an opposing wall of the enclosure; and
a spring for suspending the diaphragm from the support member.

10 . The optical microphone of claim 8 wherein the reflector comprises a reflective plate mounted directly to an inner surface of the wall.

11 . The optical sensor of claim 8 wherein the reflector comprises a reflective coating applied to an inner surface of the wall.

12 . The optical sensor of claim 8 further comprising circuitry connected to the diaphragm and the reflector, the circuitry operable to apply a voltage one or more of the diaphragm and the reflector to tune the distance.

13 . The optical sensor of claim 12 wherein the distance is tuned by moving the diaphragm while the reflector remains stationary.

14 . The optical sensor of claim 8 wherein a vertical position of the reflector with respect to the wall is fixed.

15 . An optical microphone system comprising:
a MEMS microphone enclosure having an acoustic port; a reflector formed on an inner surface of the enclosure; a diaphragm positioned within the enclosure, the diaphragm having a grating that is spaced a distance from the reflector; a light emitter positioned on an inner surface of the enclosure that is different from the reflector, the light emitter configured to transmit a laser light toward the grating and the reflector; a light detector positioned along the same inner surface as the light emitter, the light detector configured to detect an interference pattern of the laser light after reflection from the reflector; and circuitry connected to one or more of the diaphragm and the reflector.

16 . The system of claim 15 wherein the reflector comprises a gold coating applied to the inner surface of the enclosure.

17 . The system of claim 15 wherein the circuitry is operable to apply a voltage to the diaphragm to tune the distance between the grating and the reflector.

18 . The system of claim 17 wherein the voltage is used to tune the distance to any integer multiple of ¼ λ of the laser light.

19 . The system of claim 15 wherein the reflector is fixedly attached to the inner surface of the enclosure.

20 . The system of claim 15 wherein the reflector is formed on the inner surface of a bottom wall of the enclosure and the light emitter and the light detector are formed on the inner surface of a top wall of the enclosure.

Assignees

• Apple Inc

Inventors

• Lee Jae H
• Agashe Janhavi S

Classifications

• H04R2201/003

  Mems transducers or their use · CPC title

• H04R1/08 Primary

  Mouthpieces; {Microphones;} Attachments therefor · CPC title

• H04R23/008 Primary

  using optical signals for detecting or generating sound · CPC title

• H04R7/18

  at the periphery · CPC title

• H04R2307/207

  Shape aspects of the outer suspension of loudspeaker diaphragms · CPC title