Ultrasonic transducer

1. An ultrasonic transducer, comprising:

a piezoceramic element with a first surface, a second surface opposite to said first surface across said piezoceramic element and a lateral surface connecting said first surface and said second surface;

a first acoustic matching layer comprising a base and a sidewall extending from an edge of said base, wherein said base is provided with a third surface and a fourth surface opposite to said third surface across said base, and said third surface is attached with said second surface of said piezoceramic element, and an inner surface of said sidewall of said first acoustic matching layer is attached with said lateral surface of said piezoceramic element, and wherein a thickness of said base of said first acoustic matching layer is smaller than ¼ wavelength of an ultrasonic wave emitted by said piezoceramic element in said first acoustic matching layer in an operating frequency of said ultrasonic transducer, and a height of said sidewall of said first acoustic matching layer is larger than 1/20 height of said lateral surface of said piezoceramic element; and

a second acoustic matching layer with a fifth surface and a sixth surface opposite to said fifth surface across said second acoustic matching layer, and said fifth surface is attached with said fourth surface of said first acoustic matching layer.

2. The ultrasonic transducer of claim 1 , further comprising a barrel-shaped carrier with a carrier base and a carrier sidewall, wherein said barrel-shaped carrier is provided with a seventh surface and an eighth surface opposite to said seventh surface across said carrier base, and said piezoceramic element, said first acoustic matching layer and said second acoustic matching layer are disposed in said barrel-shaped carrier, and said seventh surface of said carrier base of said barrel-shaped carrier is attached with said sixth surface of said second acoustic matching layer.

3. The ultrasonic transducer of claim 2 , further comprising a damping element disposed in said barrel-shaped carrier and encapsulating said piezoceramic element, said first acoustic matching layer and said second acoustic matching layer.

4. The ultrasonic transducer of claim 1 , further comprising a tubular carrier with an inner surface, an outer surface opposite to said inner surface across said tubular carrier, a first opening and a second opening opposite to said first opening across said tubular carrier, and a damping element encapsulating said piezoceramic element, said first acoustic matching layer and said second acoustic matching layer, wherein said inner surface of said tubular carrier surrounds and contacts said damping element, and said sixth surface of said second acoustic matching layer is exposed from said first opening of said tubular carrier.

5. The ultrasonic transducer of claim 4 , wherein an edge of said fifth surface of said second acoustic matching layer is attached with one end of said tubular carrier at said first opening.

6. The ultrasonic transducer of claim 1 , wherein said second acoustic matching layer is provided with a sidewall extending from an edge of said second acoustic matching layer, and said sidewall of said second acoustic matching layer is attached with said sidewall of said first acoustic matching layer.

7. The ultrasonic transducer of claim 1 , wherein said first acoustic matching layer comprises organic polymer materials or composite materials made of organic polymer materials mixing with hollow particles or solid particles, and a material of said organic polymer materials comprises epoxy, vinyl ester resin, acrylic resin, polyurethane or UV resin.

8. The ultrasonic transducer of claim 7 , wherein said first acoustic matching layer further comprises solid particle, organic fiber, inorganic fiber or mesh sheet to control a thickness of said base of said first acoustic matching layer.

9. The ultrasonic transducer of claim 1 , wherein said second acoustic matching layer comprises organic polymer materials or composite materials made of organic polymer materials mixing with hollow particles or solid particles, and said organic polymer materials comprises epoxy, vinyl ester resin, UV resin, polyurethane, acrylic resin or cyanate ester resin.

10. The ultrasonic transducer of claim 1 , wherein said piezoceramic element comprises solid piezoceramic material in a shape of square, polygon or circle, or ringlike piezoceramic material, or multilayer piezoceramic material, or a piezoceramic material with grooves.

11. The ultrasonic transducer of claim 2 , wherein a material of said barrel-shaped carrier is selected from metallic materials of following group or the combination thereof: aluminum, titanium, copper, stainless steel, or is selected from non-metallic materials of following group or the combination thereof: glass, acrylic, polytetrafluoroethylene (PTFE), polyvinylidene difluoride (PVDF), polypropylene (PP), polyethylene (PE), polyvinyl chloride (PVC), polybutylene terephthalate (PBT), acrylonitrile butadiene styrene (ABS), polyphenylene sulfide (PPS), liquid-crystal polymer (LCP) or polyether ether ketone (PEEK).

12. The ultrasonic transducer of claim 4 , wherein a material of said tubular carrier is selected from metallic materials of following group or the combination thereof: aluminum, titanium, copper, stainless steel, or is selected from non-metallic materials of following group or the combination thereof: glass, acrylic, polytetrafluoroethylene (PTFE), polyvinylidene difluoride (PVDF), polypropylene (PP), polyethylene (PE), polyvinyl chloride (PVC), polybutylene terephthalate (PBT), acrylonitrile butadiene styrene (ABS), polyphenylene sulfide (PPS), liquid-crystal polymer (LCP) or polyether ether ketone (PEEK).