Ultrasound probe and ultrasound diagnostic apparatus

1. An ultrasound probe comprising:

a piezoelectric body that transmits and receives ultrasound for obtaining images of internal forms of a living subject;

a backing that is disposed behind the piezoelectric body; and

a reflector that is disposed between the piezoelectric body and the backing and that has an acoustic impedance greater than an acoustic impedance of the piezoelectric body; and

a plurality of intermediate layers disposed between the reflector and the backing, each intermediate layer of the plurality of intermediate layers having an acoustic impedance different from an acoustic impedance of the reflector and an acoustic impedance of the backing,

wherein an acoustic impedance of an intermediate layer of the plurality of intermediate layers nearer to the reflector is less than an acoustic impedance of an intermediate layer of the plurality of intermediate layers nearer to the backing,

wherein, a thickness of the piezoelectric body is approximately 0.25λ and a thickness of the reflector is within the range of more than 0 to less than 0.05λ, where λ is a wavelength of the ultrasound, and

wherein at least one intermediate layer of the plurality of intermediate layers has a substantially uniform thickness or has an uneven thickness that varies continuously, gradually, regularly, or irregularly.

2. The ultrasound probe according to claim 1 , wherein the thickness of the reflector is within the range of 0.01λ to less than 0.05λ, where λ is the wavelength of the ultrasound.

3. The ultrasound probe according to claim 1 , wherein the reflector has an uneven thickness that varies continuously, gradually, regularly, or irregularly.

4. The ultrasound probe according to claim 1 , wherein the reflector has an uneven thickness and has an uneven pattern on a surface facing away from the piezoelectric body.

5. The ultrasound probe according to claim 1 , wherein a plurality of materials of the plurality of intermediate layers are conductive.

6. An ultrasound probe comprising:

a piezoelectric body that transmits and receives ultrasound for obtaining images of internal forms of a living subject;

a backing that is disposed behind the piezoelectric body; and

a reflector that is disposed between the piezoelectric body and the backing and that has an acoustic impedance greater than an acoustic impedance of the piezoelectric body; and

an intermediate layer disposed between the reflector and the backing, the intermediate layer having an acoustic impedance different from an acoustic impedance of the reflector and an acoustic impedance of the backing,

wherein, a thickness of the piezoelectric body is 0.25λ and a thickness of the reflector is within the range of more than 0 to less than 0.05λ, where λ is a wavelength of the ultrasound, and

wherein the intermediate layer has an uneven thickness with an uneven pattern that varies irregularly such that ultrasound transmitted from the reflection layer to the intermediate layer is scattered by the uneven pattern.

7. The ultrasound probe according to claim 6 , wherein the thickness of the reflector is within the range of 0.01λ to less than 0.05λ, where λ is the wavelength of the ultrasound.

8. The ultrasound probe according to claim 6 , wherein the intermediate layer has an acoustic impedance that is greater than the acoustic impedance of the backing.

9. The ultrasound probe according to claim 6 , wherein the thickness td of the reflection layer relative to the wavelength of the ultrasound, the acoustic impedance Zm of the intermediate layer, and a thickness tm of the intermediate layer relative to the wavelength of the ultrasound are in an area surrounded by a polyhedron with vertexes respectively at Points A 1 to A 18 in orthogonal coordinates (td, Zm, tm) of td, Zm, and tm:

Point A 1 (0.01, 4, 0.02);

Point A 2 (0.01, 4, 0.12);

Point A 3 (0.01, 16, 0.02);

Point A 4 (0.01, 16, 0.34);

Point A 5 (0.01, 28, 0.02);

Point A 6 (0.01, 28, 0.08);

Point A 7 (0.03, 4, 0.02);

Point A 8 (0.03, 4, 0.12);

Point A 9 (0.03, 16, 0.02);

Point A 10 (0.03, 16, 0.42);

Point A 11 (0.03, 28, 0.4);

Point A 12 (0.03, 28, 0.5);

Point A 13 (0.049, 4, 0.02);

Point A 14 (0.049, 4, 0.12);

Point A 15 (0.049, 16, 0.18);

Point A 16 (0.049, 16, 0.42);

Point A 17 (0.049, 28, 0.42); and

Point A 18 (0.049, 28, 0.5).

10. The ultrasound probe according to claim 6 ,

wherein the intermediate layer comprises a plurality of intermediate layers,

wherein an acoustic impedance of an intermediate layer nearer to the reflector is less than an acoustic impedance of an intermediate layer nearer to the backing.

11. The ultrasound probe according to claim 6 , wherein a material of the intermediate layer is conductive.

12. The ultrasound probe according to claim 6 , wherein the intermediate layer comprises an insulative or semiconductive material, and a conductor that is disposed around the insulative or semiconductive material or that penetrates the insulative or semiconductive material.

13. The ultrasound probe according to claim 6 , wherein the intermediate layer has the uneven pattern on a surface facing away from the reflector.

14. An ultrasound diagnostic apparatus comprising:

the ultrasound probe according to claim 6 ;

a transmitter that generates a driving signal and outputs the driving signal to the ultrasound probe; and

an image generator that generates ultrasound image data based on a reception signal input from the ultrasound probe.

15. The ultrasound probe according to claim 6 , wherein the intermediate layer has an acoustic impedance within a range including 4 to 28 MRayls.

16. The ultrasound probe according to claim 6 , wherein the reflector has an even or uneven thickness.

17. The ultrasound probe according to claim 16 , wherein the reflector has an uneven thickness that varies continuously, gradually, regularly, or irregularly.

18. The ultrasound probe according to claim 16 , wherein the reflector has an uneven thickness and has an uneven pattern on a surface facing away from the piezoelectric body.