US 8,948,603 B2Granted

Optical microphone

AssigneePanasonic Intellectual Property Management Co., Ltd.

InventorsTakuya Iwamoto, Masahiko Hashimoto, Ushio Sangawa, Yuriko Kaneko

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Abstract

An optical microphone includes: a propagation medium portion; a light source to output a light wave passing through the propagation medium portion across the acoustic wave propagating through the propagation medium portion; a reflecting section to retroreflect the light wave having passed through the propagation medium portion; and a photoelectric conversion section to receive the light wave having been reflected by the reflecting section and passed through the propagation medium portion to output an electric signal. 0th-order, +1st-order and −1st-order diffracted light waves are respectively produced on outward and return paths, by virtue of a refractive index distribution across the propagation medium portion caused by the propagation of the acoustic wave therethrough. The photoelectric conversion section detects interference light between the +1st-order or −1st-order diffracted light wave of the outward path and the −1st-order or +1st-order diffracted light wave of the return path.

Claims20

Dependent claims

An optical microphone for detecting an acoustic wave propagating through an environment fluid by using a light wave, the optical microphone comprising:

a propagation medium portion through which the acoustic wave propagates;
a light source configured to output a light wave passing through the propagation medium portion across the acoustic wave propagating through the propagation medium portion;
a reflecting section configured to retroreflect the light wave having passed through the propagation medium portion;
and
a photoelectric conversion section configured to receive the light wave having been reflected by the reflecting section and passed through the propagation medium portion to output an electric signal, wherein:
on an outward path along which the light wave output from the light source passes through the propagation medium portion, a 0th-order diffracted light wave, a +1st-order diffracted light wave and a −1st-order diffracted light wave are produced by virtue of a refractive index distribution across the propagation medium portion caused by the propagation of the acoustic wave therethrough;
on a return path along which the 0th_order diffracted light wave having been produced on the outward path passes through the propagation medium portion after being reflected by the reflecting section, a 0th-order diffracted light wave, a +1st-order diffracted light wave and a −1st-order diffracted light wave are produced by virtue of a refractive index distribution across the propagation medium portion caused by the propagation of the acoustic wave therethrough;
and
the photoelectric conversion section detects at least one of interference light between the +1st-order diffracted light wave produced on the outward path and the −1st-order diffracted light wave produced on the return path, and interference light between the −1st-order diffracted light wave produced on the outward path and the +1st-order diffracted light wave produced on the return path.

6 more elements

A flaw detection device comprising:

a sound source configured to generate an acoustic wave in a subject;
a light source configured to output a light wave passing through the subject across a reflected wave of the acoustic wave caused by a flaw in the subject;
a reflecting section configured to retroreflect the light wave having passed through the subject;
and
a photoelectric conversion element array including a plurality of photoelectric conversion elements for receiving the light wave having been reflected by the reflecting section and passed through the subject to output an electric signal, wherein:
on an outward path along which the light wave output from the light source passes through the subject, a 0th-order diffracted light wave, a +1st-order diffracted light wave and a −1st-order diffracted light wave are produced from the light wave by virtue of a refractive index distribution across the subject caused by the propagation of the reflected wave therethrough;
on a return path along which the 0th-order diffracted light wave having been produced on the outward path passes through the subject as a result of the reflection by the reflecting section, a 0th-order diffracted light wave, a +1st-order diffracted light wave and a −1st-order diffracted light wave are produced from the 0th-order diffracted light on the outward path by virtue of the refractive index distribution across the subject caused by the propagation of the reflected wave;
the photoelectric conversion element array detects, using one or more of the plurality of photoelectric conversion elements, at least one of a first interference light wave obtained as a result of interference between the +1st-order diffracted light wave produced on the outward path and the −1st-order diffracted light wave produced on the return path, and a second interference light wave obtained as a result of interference between the −1st-order diffracted light wave produced on the outward path and the +1st-order diffracted light wave produced on the return path;
a propagation direction of the reflected wave is identified based on a position or positions, in the photoelectric conversion element array, of the one or more of the photoelectric conversion elements that have detected at least one of the first interference light wave and the second interference light wave;
a distance over which the reflected wave propagates through the subject is calculated based on a time when at least one of the first interference light wave and the second interference light wave is detected by the photoelectric conversion element array and a time of generation of the acoustic wave in the subject;
and
a position of the flaw in the subject is estimated from the identified propagation direction and the calculated distance.

9 more elements

An acoustic wave detection method for detecting an acoustic wave using a light wave, the method comprising the steps of:

(A) propagating an acoustic wave through a propagation medium portion;
(B) causing a light wave to pass across the acoustic wave propagating through the propagation medium portion, thereby producing a 0th-order diffracted light wave, a +1st-order diffracted light wave and a −1st-order diffracted light wave by virtue of a refractive index distribution across the propagation medium portion caused by the propagation of the acoustic wave therethrough;
(C) retroreflecting the 0th-order diffracted light wave, the +1st-order diffracted light wave and the −1st-order diffracted light wave produced in the step (B);
(D) causing the retroreflected 0th-order diffracted light wave to pass across the acoustic wave propagating through the propagation medium portion, thereby producing a +1st-order diffracted light wave and a −1st-order diffracted light wave by virtue of a refractive index distribution across the propagation medium portion caused by the propagation of the acoustic wave therethrough;
and
(E) detecting, using a photoelectric conversion element array including a plurality of photoelectric conversion elements, at least one of a first interference light wave between the +1st-order diffracted light wave having been produced in the step (B) and retroreflected and the −1st-order diffracted light wave produced in the step (D), and a second interference light wave between the −1st-order diffracted light wave having been produced in the step (B) and retroreflected and the +1st-order diffracted light wave produced in the step (D), and identifying a propagation direction of the acoustic wave based on a position or positions, in the photoelectric conversion element array, of the one or more of the photoelectric conversion elements that have detected at least one of the first interference light wave and the second interference light wave.

3 more elements

Dependencies are inferred from the claim text.

Facts

Application: 13/752,817Filed 29 Jan 2013 · continuation
Priority: JP 2011-06296522 Mar 2011
Published: US 2013/0142519 A16 Jun 2013
Granted: 3 Feb 2015
Term ends: Not estimatedThe source records don’t support an estimate.

Classification4 codes

H04R 23/008
Transducers other than those covered by groups H04R9/00 - H04R21/00: using optical signals for detecting or generating sound
G01H 9/00
Measuring mechanical vibrations or ultrasonic, sonic or infrasonic waves by using radiation-sensitive
H04R
Loudspeakers, microphones, gramophone pick-ups or like acoustic electromechanical transducers
G01H
Measurement of mechanical vibrations or ultrasonic, sonic or infrasonic waves