Transducer hydrophone with filled reservoir
First Claim
1. A hydrophone device for use in probing the acoustic properties of a fluid medium, comprising:
- supporting hoop means of a selected area;
first sheet means of biaxially oriented polymer material secured in said hoop means and held thereby in a taut condition;
means having a poled piezoelectrically active area of predetermined size, the selected area of said first sheet means defined by said hoop means being larger than the size of said poled piezoelectrically active area, and said poled piezoelectrically active area being located in said first sheet means and spaced from said hoop means such that said hoop means during use remains outside, and said poled piezoelectrically active area remains inside, the region of the medium subjected to the acoustic energy and the point being probed by said hydrophone device, said sheet means having respective outer and inner electrode means of electrically conductive material on opposite outer and inner surfaces of said poled piezoelectrically active area, said first sheet means having a thickness selected such that it is substantially acoustically transparent in said fluid medium, and first and second electrical leads on said first sheet means, electrically connected to said inner and outer electrode means, respectively, and extending toward the periphery of said first sheet means, said second electrical lead electrically connected to said hoop means, said hoop means connected to an outer conductor of a coaxial connector, said first electrical lead electrically connected to an inner conductor of said coaxial connector;
an electrically conductive coating on the entire outer surface of said first sheet means, and in electrical contact with said hoop means;
a reservoir defined by the inner surface of said first sheet means, said hoop means, and an electrically conductive backing means secured to and electrically connected to said hoop means and spaced from the inner surface of said first sheet means, said reservoir being filled by a low-dielectric constant material having an acoustic impedance which is about equal to that of said medium, a dielectric constant of less than about 4 and a volume resistivity of greater than about 1014 ohm-cm.
1 Assignment
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Accused Products
Abstract
A hydrophone device with one or more very small active spots located on a large continuous ferroelectric sheet, such as PVDF, overcomes many of the problems in prior art constructions associated with the high dielectric constant of various media in which the device is used. Additional improvements include increased signal to noise ratio and a sensitivity independent of the medium properties. The hydrophone device includes a piezoelectrically active sheet stretched and clamped on over the top of a hoop ring. A backing is attached to the back of the hoop ring. A low-dielectric material fills the space between the backing and the sheet. This material eliminates the capacitive loading effect which would otherwise be presented by the medium being probed.
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Citations
18 Claims
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1. A hydrophone device for use in probing the acoustic properties of a fluid medium, comprising:
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supporting hoop means of a selected area; first sheet means of biaxially oriented polymer material secured in said hoop means and held thereby in a taut condition; means having a poled piezoelectrically active area of predetermined size, the selected area of said first sheet means defined by said hoop means being larger than the size of said poled piezoelectrically active area, and said poled piezoelectrically active area being located in said first sheet means and spaced from said hoop means such that said hoop means during use remains outside, and said poled piezoelectrically active area remains inside, the region of the medium subjected to the acoustic energy and the point being probed by said hydrophone device, said sheet means having respective outer and inner electrode means of electrically conductive material on opposite outer and inner surfaces of said poled piezoelectrically active area, said first sheet means having a thickness selected such that it is substantially acoustically transparent in said fluid medium, and first and second electrical leads on said first sheet means, electrically connected to said inner and outer electrode means, respectively, and extending toward the periphery of said first sheet means, said second electrical lead electrically connected to said hoop means, said hoop means connected to an outer conductor of a coaxial connector, said first electrical lead electrically connected to an inner conductor of said coaxial connector; an electrically conductive coating on the entire outer surface of said first sheet means, and in electrical contact with said hoop means; a reservoir defined by the inner surface of said first sheet means, said hoop means, and an electrically conductive backing means secured to and electrically connected to said hoop means and spaced from the inner surface of said first sheet means, said reservoir being filled by a low-dielectric constant material having an acoustic impedance which is about equal to that of said medium, a dielectric constant of less than about 4 and a volume resistivity of greater than about 1014 ohm-cm. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18)
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Specification