Transducer system

Abstract

A device ( 100 ) for converting an acoustic signal ( 102 ) into an electric signal ( 104 ), wherein the device ( 100 ) includes an interferometer ( 106 ) including two mirrors ( 108 ) adapted for reflecting electromagnetic radiation ( 112 ) coupled into a space ( 110 ) between the mirrors ( 108 ). The acoustic signal ( 102 ) is to be coupled into the space ( 110 ) for influencing the electromagnetic radiation ( 112 ) in accordance with this acoustic signal. An electromagnetic radiation detector ( 112 ) is adapted for detecting the influenced electromagnetic radiation ( 112 ) and for converting the detected influenced electromagnetic radiation ( 112 ) into the electric signal ( 104 ) being indicative for the acoustic signal ( 102 ). An operation point stabilization unit stabilizes an operation point of the device ( 100 ).

What is claimed is: 
     
         1 . A device for converting an acoustic signal into an electric signal, comprising:
 an interferometer;   said interferometer including two spaced mirrors configured to at east partial reflect electromagnetic radiation coupled into a space between said mirrors, said space receiving an acoustic signal influencing the electromagnetic radiation;   said mirrors being arranged plane parallel to each other and spatially fixed relative to each other;   an electromagnetic radiation source configured to generate the electromagnetic radiation coupled into said space between said mirrors;   an electromagnetic radiation detector configured to detect the electromagnetic radiation influenced by the acoustic signal and to generate an electric signal indicative of the acoustic signal; and,   an operation point stabilization unit configured to stabilize interferometer operation by controlling an electric drive current powering said electromagnetic radiation source, said operation point stabilization unit including a feedback loop from said electromagnetic radiation detector.   
     
     
         2 . The device for converting an acoustic signal into an electric signal as claimed in  claim 1 , wherein:
 said interferometer is selected from the group consisting of a Fabry-Perot interferometer, an etalon and a Gires-Tournois arrangement.   
     
     
         3 . The device for converting an acoustic signal into an electric signal as claimed in  claim 1 , wherein:
 said mirrors reflect optical light coupled into said space between said mirrors.   
     
     
         4 . The device for converting an acoustic signal into an electric signal as claimed in  claim 1 , wherein:
 said electromagnetic radiation detector includes a photodiode.   
     
     
         5 . The device for converting an acoustic signal into an electric signal as claimed in  claim 1 , wherein:
 said electromagnetic radiation detector is mechanically attached directly on one of said mirrors.   
     
     
         6 . The device for converting an acoustic signal into an electric signal as claimed in  claim 1 , wherein:
 said electromagnetic radiation source includes a laser.   
     
     
         7 . The device for converting an acoustic signal into an electric signal as claimed in  claim 1 , wherein:
 said electromagnetic radiation source is mechanically attached directly on one of said mirrors.   
     
     
         8 . A device for converting an acoustic signal into an electric signal as claimed in  claim 1 , further comprising:
 a second electromagnetic radiation detector integrated in said electromagnetic radiation source.   
     
     
         9 . A device for converting an acoustic signal into an electric signal as claimed in  claim 1 , further comprising:
 a second electromagnetic radiation detector attached to said electromagnetic radiation source.   
     
     
         10 . A device for converting an acoustic signal into an electric signal as claimed in  claim 9 , further comprising:
 a differential amplifier, said differential amplifier having a first input coupled to said electromagnetic radiation detector, said differential amplifier having a second input coupled to said second electromagnetic radiation detector, and said differential amplifier having an output providing the electric signal indicative of the acoustic signal.   
     
     
         11 . A device for converting an acoustic signal into an electric signal as claimed in  claim 1 , further comprising:
 an amplifier, said amplifier having an input coupled to said electromagnetic radiation detector, and said amplifier having an output providing the electric signal indicative of the acoustic signal.   
     
     
         12 . A device for converting an acoustic signal into an electric signal as claimed in  claim 1 , further comprising:
 a rigid connection element rigidly connecting said mirrors to one another to delimit the space between the mirrors.   
     
     
         13 . A device for converting an acoustic signal into an electric signal as claimed in  claim 1 , further comprising:
 said operation point stabilization unit including an electric signal separator configured to separate the electrical signal generated by said electromagnetic radiation detector into direct current component and into alternating current component indicative of the acoustic signal.   
     
     
         14 . A device for converting an acoustic signal into an electric signal as claimed in  claim 1 , further comprising:
 each of said two mirrors having a respective reflective surface, each of said two respective reflective surfaces mutually facing one another; and,   each of said two mirrors having a respective non-reflective surface opposing its own respective corresponding reflective surface and being respectively covered with a respective antireflection coating.   
     
     
         15 . A method of converting an acoustic signal into an electric signal, comprising the steps of:
 at least partially reflecting electromagnetic radiation coupled into a space between an interferometer's two mirrors arranged plane parallel to each other and spatially fixed relative to each other;   generating with an electromagnetic radiation source the electromagnetic radiation coupled into the space between the mirrors;   coupling an acoustic signal into the space between the mirrors to influence the electromagnetic radiation;   detecting the influenced electromagnetic radiation with an electromagnetic radiation detector to generate an electric signal indicative of the acoustic signal; and,   controlling an electric drive current powering the electromagnetic radiation source to stabilize interferometer operation via an operation point stabilization unit including a feedback loop from the electromagnetic radiation detector.   
     
     
         16 . A method of converting an acoustic signal into an electric signal as claimed in  claim 15 , further comprising the steps of:
 monitoring at least one parameter indicative of a present operation point of the interferometer to determine a deviation from a predefined target operation point; and,   upon determining the deviation from the predefined target operation point, controlling the electromagnetic radiation source to return to the predefined target operation point.   
     
     
         17 . A method of converting an acoustic signal into an electric signal as claimed in  claim 15 , further comprising the step of:
 generating with the electromagnetic radiation source electromagnetic radiation modulated on a carrier wave in the high frequency domain.   
     
     
         18 . A method of converting an acoustic signal into an electric signal as claimed in  claim 15 , further comprising the step of:
 generating with the electromagnetic radiation source divergent electromagnetic radiation between the two mirrors.   
     
     
         19 . A method of converting an acoustic signal into an electric signal as claimed in  claim 15 , further comprising the step of:
 adjusting with the operation point stabilization unit an electric drive current powering the electromagnetic radiation source to adjust the wavelength of the electromagnetic radiation in order to adjust the operating point.   
     
     
         20 . A method of converting an acoustic signal into an electric signal as claimed in  claim 15 , further comprising the steps of:
 supplying an operation point stabilization unit feedback circuit with a direct current component;   determining an actual operating point based on the supplied direct current component; and,   controlling the electromagnetic radiation source to drive the interferometer towards a predefined reference operating point.