EP0436437A1 - Transducteur optoacoustique - Google Patents

Transducteur optoacoustique Download PDF

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Publication number
EP0436437A1
EP0436437A1 EP90403766A EP90403766A EP0436437A1 EP 0436437 A1 EP0436437 A1 EP 0436437A1 EP 90403766 A EP90403766 A EP 90403766A EP 90403766 A EP90403766 A EP 90403766A EP 0436437 A1 EP0436437 A1 EP 0436437A1
Authority
EP
European Patent Office
Prior art keywords
cavity
membrane
light
transducer according
optoacoustic transducer
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP90403766A
Other languages
German (de)
English (en)
French (fr)
Inventor
Jamal Housni
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Societe Industrielle de Liaisons Electriques SA
Original Assignee
Societe Industrielle de Liaisons Electriques SA
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Societe Industrielle de Liaisons Electriques SA filed Critical Societe Industrielle de Liaisons Electriques SA
Publication of EP0436437A1 publication Critical patent/EP0436437A1/fr
Withdrawn legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R23/00—Transducers other than those covered by groups H04R9/00 - H04R21/00
    • H04R23/008—Transducers other than those covered by groups H04R9/00 - H04R21/00 using optical signals for detecting or generating sound

Definitions

  • the present invention relates to an optoacoustic transducer.
  • Optical fibers are being used more and more for the transmission of voice communications, optical fibers having the advantage of being insensitive to electromagnetic disturbances and being able moreover to be used in complete safety in environments presenting a risk of explosion.
  • optical fibers for voice communications remains however limited by the possibility of transforming the light signal conveyed by the optical fiber into an acoustic signal which can be perceived by the user.
  • optoacoustic transducers comprising a cavity into which opens a light transmitting member fixed on one side thereof, and absorption means arranged in the cavity for absorbing light and converting it into heat, the cavity comprising, where appropriate, a wall part formed by a flexible membrane. It has been found that in the transducers of the prior art the temperature variations resulting from the light modulations were not fast enough to accurately translate the light modulations.
  • An object of the present invention is to provide an improved optoacoustic transducer.
  • an optoacoustic transducer comprising a cavity communicating with a light transmitting member fixed on one side thereof and absorption means arranged in the cavity for absorbing the light and convert it into heat, the cavity comprising a wall part formed by a flexible membrane, characterized in that it comprises means for ensuring an accelerated diffusion of the light in the absorption means.
  • the device according to the invention allows this absorption to be carried out on a surface, carried by the membrane, the local temperature variations of the air in the vicinity of this surface then being sufficient to vibrate the membrane.
  • the flexible membrane comprises a substantially rigid central part hingedly connected to a peripheral part.
  • the central part functions like a piston and the acoustic efficiency is improved compared to a membrane operating in an elastic deformation mode.
  • the cavity has a wall facing the membrane having a conformation surface substantially identical to the membrane.
  • the internal volume of the cavity is then in the form of a gas layer of substantially constant thickness favorable to a large amplitude of the vibrations of the membrane and therefore ensuring a further improved acoustic efficiency.
  • the transducer comprises a light diffusing member disposed at one end of the light transmitting member. This increases the speed of transformation of light into heat and therefore the efficiency of the transducer.
  • the transducer comprises a tubular cylindrical body 2 in which is mounted an optical fiber support sleeve 3 fixed inside the tubular body 2 and comprising a cylindrical channel 4 ending at a end by an annular shoulder 5 projecting towards the inside of the channel 4.
  • a spherical lens 6 is disposed in the channel 4 and bears against the shoulder 5.
  • An optical fiber, or a bundle of optical fibers 7 is also mounted in channel 4 with its end in contact with the spherical lens 6. The sheath 8 of the optical fiber is tightly fixed inside the channel 4.
  • the end of the sleeve 3 has a flat annular surface 9 on which an annular washer 10 is supported.
  • the annular surface 11 of the end of the sleeve 3 adjacent to the annular surface 9 has a convex curvature in the form of an arc of a circle according to an axial section of the sleeve 3.
  • the membrane 12 is produced from a semi-rigid plastic film formed to comprise a central part 13 in the form of a spherical cap connected to an annular peripheral part 14 of section in an arc of a circle, this peripheral part being itself connected to an annular collar 15 bearing on the annular washer 10.
  • the membrane 12 thus delimited with the annular washer 10, the end of the sleeve 3 and the spherical lens 6, a sealed cavity 16 into which the transmitting lens 6 opens out. the lumen and a part of the wall of which is formed by the flexible membrane 12.
  • the central part is substantially rigid and hingedly connected to the peripheral part 14.
  • the radii of curvature of the central part 13 and of the peripheral part 14 are respectively homothetic to the radii of curvature of the spherical lens 6 and of the curved annular zone 11 of the end of the sleeve 3, so that the facing surfaces are substantially identical and delimit between them a layer of air of substantially constant thickness.
  • An annular washer 17 is supported on the flange 15 of the membrane 12 on the side opposite to the annular washer 10.
  • the annular washer 17 is kept applied against the membrane 12 by a plug 18 screwed into the body 2.
  • the plug 18 has a acoustic conduit 19 opposite the central part 13 of the membrane 12 and its end surface has a shape identical to the opposite face of the membrane 12 so as to delimit therewith an air layer of substantially constant thickness forming a compression chamber 20.
  • the acoustic conduit 19 is extended outwardly by a slightly frustoconical cavity 21 used for the establishment of a pavilion whose dimensions are adapted to the equivalent impedance produced by the membrane 12 and the volume of the cavity 16, as well as the frequencies which it is desired to be able to listen to by means of the transducer according to the invention.
  • the cavity 16 is preferably equipped with means for absorbing the light and converting it into heat. These means are constituted either by carbon black introduced into the material forming the walls of the cavity 16, or by carbon fibers placed inside the cavity 16, or even carbon black particles in suspension in the cavity. In these latter cases, the membrane 12 preferably comprises a reflective coating 22 on its face facing the interior of the cavity 16.
  • the transducer comprises a one-piece body 23 in which the cavity 16 is hollowed out.
  • the optical fiber 7 equipped with its sheath is fixed in a channel 4 which this time extends opposite a edge of the central part 13 of the membrane 12 so that the light which leaves the optical fiber 7 is then reflected in different directions by the reflecting surface of the membrane 12.
  • the cavity 16 is equipped as previously means of absorption by volume.
  • the membrane 12 is held in place by a circular ring 24 itself fixed to the block 23 by any suitable means, for example by bonding 25.
  • the cavity 16 is not completely sealed but is connected to the open air by a small pressure balancing channel 26.
  • This balancing channel is only intended to compensate for variations in static pressure between the cavity 16 and the external environment in order to avoid permanent deformation of the membrane when the surrounding atmospheric pressure varies.
  • the channel 26 has a very small diameter, for example of the order of 0.2 mm and a great length relative to its diameter, for example several millimeters, so that it appears as an opening opposite. of static pressure but as a tight wall with respect to rapid variations in pressure as they are generated by light power modulations.
  • Such a balancing channel can of course also be provided in the first embodiment.
  • FIG. 3 illustrates a third embodiment in which the body 23 is made in two parts joined to each other to form a first cavity part 16.1 with a substantially spherical reflecting rigid wall into which the optical fiber 7 opens, and a second cavity part 16.2, a wall part of which is formed by a membrane 12 kept fixed to the body 23 by a ring 24 as in the second embodiment.
  • the first and the second cavity part are connected to each other by an orifice 27 having dimensions suitable for transmitting the pressure variations coming from the first cavity part 16.1.
  • the orifice 27 has for example a diameter of the order of 0.8 mm and a length shorter than the diameter, for example 0.5 mm.
  • the first part of cavity 16.1 preferably contains absorption means in volume as before and the reflecting walls ensure multiple reflections of the light rays so that the energy which they transport is very quickly transformed into heat one thus obtains a transducer which not only has good overall optoacoustic performance, but also good dynamic performance.
  • FIG. 4 illustrates an embodiment in which the absorption of light takes place at the surface.
  • the membrane 12 this time comprises a flat central part disposed opposite an optical fiber or a bundle of optical fibers 7 and carries a thin layer of absorbent material 28 facing the end of the bundle 7.
  • the absorbent layer 28 is preferably thermally insulated from the membrane by an insulating pad 29.
  • a light diffusing member has been provided in the form of a spherical lens arranged at the end of the fiber 7, the spherical lens 6 may be replaced by another light-diffusing member, for example an elliptical or other lens or by a blooming of a bundle of fibers inside the cavity 16, or by conical termination of an optical fiber or a bundle of optical fibers.
  • a particular gas therein for example a rare gas such as xenon.

Landscapes

  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Acoustics & Sound (AREA)
  • Signal Processing (AREA)
  • Optical Couplings Of Light Guides (AREA)
EP90403766A 1990-01-03 1990-12-26 Transducteur optoacoustique Withdrawn EP0436437A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR9000032 1990-01-03
FR9000032A FR2656761A1 (fr) 1990-01-03 1990-01-03 Transducteur optoacoustique.

Publications (1)

Publication Number Publication Date
EP0436437A1 true EP0436437A1 (fr) 1991-07-10

Family

ID=9392503

Family Applications (1)

Application Number Title Priority Date Filing Date
EP90403766A Withdrawn EP0436437A1 (fr) 1990-01-03 1990-12-26 Transducteur optoacoustique

Country Status (2)

Country Link
EP (1) EP0436437A1 (enrdf_load_stackoverflow)
FR (1) FR2656761A1 (enrdf_load_stackoverflow)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2688372A1 (fr) * 1992-03-03 1993-09-10 Silec Liaisons Elec Transducteur optoacoustique miniature.

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4002897A (en) * 1975-09-12 1977-01-11 Bell Telephone Laboratories, Incorporated Opto-acoustic telephone receiver
DE2639822B1 (de) * 1976-09-03 1977-12-08 Siemens Ag Opto-akustischer Wandler
US4590620A (en) * 1985-10-17 1986-05-20 Feldman Nathan W Optical telephone
US4689827A (en) * 1985-10-04 1987-08-25 The United States Of America As Represented By The Secretary Of The Army Photofluidic audio receiver

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4002897A (en) * 1975-09-12 1977-01-11 Bell Telephone Laboratories, Incorporated Opto-acoustic telephone receiver
DE2639822B1 (de) * 1976-09-03 1977-12-08 Siemens Ag Opto-akustischer Wandler
US4689827A (en) * 1985-10-04 1987-08-25 The United States Of America As Represented By The Secretary Of The Army Photofluidic audio receiver
US4590620A (en) * 1985-10-17 1986-05-20 Feldman Nathan W Optical telephone

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2688372A1 (fr) * 1992-03-03 1993-09-10 Silec Liaisons Elec Transducteur optoacoustique miniature.
WO1993018628A1 (fr) * 1992-03-03 1993-09-16 Societe Industrielle De Liaisons Electriques Transducteur optoacoustique miniature

Also Published As

Publication number Publication date
FR2656761B1 (enrdf_load_stackoverflow) 1997-02-07
FR2656761A1 (fr) 1991-07-05

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