Optical system for detecting acoustic wave energy in a fluid medium
First Claim
1. An optical system for generating a signal related to acoustic wave energy in a fluid medium comprising:
- a source of coherent optical radiation;
optical waveguide means for defining a first pair of optical paths adapted so that different lengths of said first pair of paths are exposed to acoustic wave energy in the fluid medium;
first means for coupling coherent optical radiation from the source into each of said first pair of optical paths;
optical waveguide means for defining a second pair of optical paths;
second means for cross coupling optical radiation from each of said first pair of paths into each of said second pair of paths, so that interference fringes are generated in said second pair of paths as the result of said acoustic wave energy, said second means being adapted so that the phase of said interference fringes in the two paths of said second pair of paths will be different and so that the difference will be substantially different from 180°
; and
signal processing means responsive to the quantity of interference fringes in a first one of said second pair of paths and to the phase relationship between the interference fringes in the second pair of paths for generating said signal related to the acoustic wave energy.
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Accused Products
Abstract
An optical sound source signature transducer system for use in marine seismic exploration in which coherent radiation from a laser is coupled to unequal length optical paths exposed to modulation by the acoustic energy wave generated by the sound source. The reflected beams from the paths are crosscoupled to generate interference fringes in two output beams out of phase with each other. The fringes in one output beam are counted in an up/down counter to determine the magnitude of the pressure as a function of time. The direction of the pressure change is determined by examination of the phase relationship between the fringes in the output beams. Peaks and valleys in the pressure are detected as phase reversals between the fringes in the output beams be detecting the beginning and end of a fringe in one beam without detecting the beginning or end of a fringe in the other beam therebetween. The direction of counting of the counter is reversed upon detection of a peak or valley in the modulating pressure to maintain the count as an accurate representation of the magnitude of the pressure.
86 Citations
20 Claims
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1. An optical system for generating a signal related to acoustic wave energy in a fluid medium comprising:
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a source of coherent optical radiation; optical waveguide means for defining a first pair of optical paths adapted so that different lengths of said first pair of paths are exposed to acoustic wave energy in the fluid medium; first means for coupling coherent optical radiation from the source into each of said first pair of optical paths; optical waveguide means for defining a second pair of optical paths; second means for cross coupling optical radiation from each of said first pair of paths into each of said second pair of paths, so that interference fringes are generated in said second pair of paths as the result of said acoustic wave energy, said second means being adapted so that the phase of said interference fringes in the two paths of said second pair of paths will be different and so that the difference will be substantially different from 180°
; andsignal processing means responsive to the quantity of interference fringes in a first one of said second pair of paths and to the phase relationship between the interference fringes in the second pair of paths for generating said signal related to the acoustic wave energy. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. An optical transducer for generating a signal related to acoustic wave energy in a fluid medium comprising:
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a fluid filled housing adapted for submersion in the fluid medium, at least a portion of the housing being formed from acoustically transparent material; means for substantially sealing the interior of the housing from the surrounding fluid; optical waveguide means within the housing for defining a first pair of optical paths having mutually different lengths exposed to the acousitc energy in the fluid medium; first means for coupling coherent optical radiation into the first pair of paths for modulation by acoustic wave energy within the fluid medium; a second pair of optical paths; second means for coupling optical radiation from each of said first pair of paths into each of said second pair of paths, so that interference fringes are generated in said second pair of paths in response to said acoustic wave energy, said second means being adapted so that the phase of said interference fringes in the two paths of said second pair of paths will be different, and said difference will be substantially different from 180°
; andsignal processing means responsive to the quantity of interference fringes in at least one of said second pair of paths and to the phase relationship between the interference fringes in the second pair of paths for generating said signal related to the acoustic wave energy.
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13. A system for generating a signal related to acoustic wave energy in a fluid medium comprising:
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a source of coherent radiation; a transducer including a first pair of optical paths adapted so that when said transducer is positioned in said fluid medium, acoustic wave energy in the fluid medium will cause the optical lengths of the two paths said first pair of paths to change by different amounts; first means for coupling optical radiation from said source into each of said first pair of paths; a second pair of optical paths; second means for coupling optical radiation from each of said first pair of paths into each of said second pair of paths, so that interference fringes are generated in said second pair of paths in response to said acoustic wave energy, said second means being adapted so that the phase of said interference fringes in the two paths of said second pair of paths will be different, and said difference will be substantially different from 180°
; andsignal processing means responsive to the quantity of interference fringes in at least one of said second pair of paths and to the phase relationship of the interference fringes in the second pair of paths for generating said signal related to the acoustic wave energy. - View Dependent Claims (14, 15, 16, 17, 18, 19, 20)
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Specification