	US 7,602,672 B2
	Quasi-self focusing high intensity and large power ultrasonic transducer
Ninglei Lai, Room 1504, Building No. 4, Yangguang Square, Longjiang Community, Nanjing City 210000 (China); Qiji Lai, Nanjing (China); Kefan Liu, Nanjing (China); and Guogan Xiong, Nanjing (China)
Assigned to Ninglei Lai, Nanjing (China)
Appl. No. 11/722,858 PCT Filed Dec. 27, 2004, PCT No. PCT/CN2004/001527 § 371(c)(1), (2), (4) Date Jun. 26, 2007, PCT Pub. No. WO2006/069467, PCT Pub. Date Jul. 06, 2006.
Prior Publication US 2008/0112582 A1, May 15, 2008
Int. Cl. H04B 1/02 (2006.01)

U.S. Cl. 367—138

9 Claims

1. A quasi-self focusing ultrasonic transducer including

a backing; and

a plurality of piezo-electric crystal sheets,

wherein:

the backing has a double layer structure and there is an air cavity between the layers,

at least four piezo-electric crystal sheets of the plurality of piezo-electric crystal sheets are adhered on an inside focusing face of the backing,

a protective layer covers a surface of the sheets;

said backing is made of a material with low loss and high acoustic resistance;

the inside focusing face of the backing is a concave spherical zone surface;

a thickness of an inner layer of the backing is an integral multiple ±35% of ½ of a wavelength of a sound wave in the backing material under a working frequency emitted by the piezo-electric crystal sheets; and

the plurality of piezo-electric crystal sheets comprise between 4 and 24 piezo-electric crystal sheets of similar electroacoustical characteristics, with a radius of curvature at all points substantially identical to that of corresponding points of the inside focusing face of the backing, the between 4 and 24 piezo-electric crystal sheets being adhered on the inside focusing face of the backing.