Acoustic impedance matching device

Claim 2

An impedance matching device for coupling wideband sonic energy between one or more acoustic transducers and an object, characterized in that it comprises a periodic array of stepped matching structures disposed side-by-side over an active surface of the transducers, each of the matching structures comprising two or more flat parallel strips of sound-conductive material which are disposed, side-by-side, over the active surface in a stepped configuration wherein the thickness of successive strips increases monotonically across the structure.

Claim 3

A device of claim 1 characterized in that the thickness of each of the parallel strips is one quarter wavelength at a frequency within the bandwidth of the coupled sound energy.

Claim 4

The device of claim 1 or 2, characterized in that the sound conductive material comprises a metal filled plastic resin.

Claim 5

The device of claim 3, characterized in that the sound conductive material comprises tungsten powder in an epoxy resin binder.

Claim 9

The device of claim 7, characterized in that the acoustic lens is a cylindrical lens.

Claim 10

A wide bandwidth acoustic transducer assembly comprising: a linear array of acoustic transducer elements formed in a sheet of piezoelectric material, the sheet having a front active surface and a rear surface which is opposite the front surface; a lossy backing layer disposed adjacent the rear surface of the sheet; characterized in that it comprises a matching device including an array of stepped matching structures disposed side-by-side over the active surface of the sheet, each of the stepped structures comprising two or more flat parallel strips of sound conductive material disposed side-by-side on the active surface in a stepped configuration wherein the thickness of successive strips increases monotonically along the width of the structure.

Claim 11

A wide bandwidth acoustic transducer assembly comprising: a linear array of acoustic transducer elements formed in a sheet of piezoelectric material, the sheet having a front active surface and a rear surface which is opposite the front surface; a lossy backing layer disposed adjacent the rear surface of the sheet; characterized in that it comprises a matching device including an array of stepped matching structures disposed side-by-side over the active surface of the sheet, each of the stepped structures comprising two or more flat parallel strips of sound conductive material disposed side-by-side on the active surface in a stepped configuration wherein the thickness of successive strips increases monotonically along the width of the structure.

Claim 12

The assembly of claim 9, characterized in that the rear surface of the sheet is grooved with a series of parallel kerfs to separate the individual transducer elements, the parallel strips of sound conductive material being disposed parallel to the kerfs.

Claim 13

The assembly of claim 10, characterized in that at least two stepped matching structures are disposed over each transducer element.

Claim 14

The assembly of claim 9, 10 or 11, further comprising electrode means for coupling electrical energy to the transducer elements, characterized in that the electrode means comprise a first electrode disposed between the active surface of the sheet and the matching device and a plurality of second electrodes, each second electrode being disposed between the rear surface of a transducer element and the backing layer.

Claim 15

The assembly of one of the claims 9-12, characterized in that it further comprises an acoustic lens disposed over the matching structure and opposite the sheet.

Claim 16

The assembly of claim 13, characterized in that the acoustic lens comprises silicone rubber.

Claim 17

The assembly of one of the claims 9-14, characterized in that the backing layer comprises glass micro-balloons in a resin binder.