Ultrasound probe

1. An ultrasound probe comprising:

an array of transducer elements in which a plurality of transducer elements are arranged two-dimensionally in a first direction corresponding to an elevation direction and in a second direction corresponding to an azimuth direction that is different from the first direction, wherein the array of transducer elements makes an interconversion between an electric pulse and an ultrasonic wave;

an acoustic lens which has a convex surface in a transmission direction of the ultrasonic wave on a cross section that is parallel to the first direction and the transmission direction and which converges ultrasonic waves transmitted from the plurality of transducer elements;

at least two acoustic adjustment layers which are made of a material that has a different sound velocity from the acoustic lens, which are respectively arranged between at least two of the transducer elements of a row of the transducer elements that are arranged in the first direction and the acoustic lens, and of which at least one of the material and a thickness of each of the at least two acoustic adjustment layers in the transmission direction are different from each other, wherein both end surfaces in the first direction of each of the acoustic adjustment layers are arranged so as to substantially coincide with both end surfaces in the first direction of respective transducer elements, and no acoustic adjustment layer is arranged between at least one of the transducer elements of the row of transducer elements and the acoustic lens; and

an acoustic matching layer through which the ultrasonic waves transmitted from the plurality of transducer elements pass.

2. The ultrasound probe of claim 1 , wherein the acoustic adjustment layers are made of a material which has a higher sound velocity than the acoustic lens, and

the closer to the center of the array of transducer elements in the first direction the transducer element associated with an acoustic adjustment layer is, the greater the thickness is.

3. The ultrasound probe of claim 2 , wherein the at least two acoustic adjustment layers include:

a first acoustic adjustment layer which is associated with the transducer element that is located at the center of the array of transducer elements in the first direction; and

a second acoustic adjustment layer which is adjacent to the first acoustic adjustment layer in the first direction, and

the first acoustic adjustment layer is thicker than the second acoustic adjustment layer.

4. The ultrasound probe of claim 1 , wherein the acoustic adjustment layers are made of a material which has a lower sound velocity than the acoustic lens, and

the closer to the center of the array of transducer elements in the first direction the transducer element associated with an acoustic adjustment layer is, the smaller the thickness is.

5. The ultrasound probe of claim 4 , wherein the at least two acoustic adjustment layers include:

a first acoustic adjustment layer which is associated with the transducer element that is located at the center of the array of transducer elements in the first direction; and

a second acoustic adjustment layer which is adjacent to the first acoustic adjustment layer in the first direction, and

the first acoustic adjustment layer is less thick than the second acoustic adjustment layer.

6. The ultrasound probe of claim 1 , wherein the acoustic adjustment layers are made of a material which has a higher sound velocity than the acoustic lens, and

the closer to the center of the array of transducer elements in the first direction the transducer element associated with an acoustic adjustment layer is, the higher the sound velocity of the material of that acoustic adjustment layer is.

7. The ultrasound probe of claim 1 , wherein the acoustic adjustment layers are made of a material which has a lower sound velocity than the acoustic lens, and

the farther away from the center of the array of transducer elements in the first direction the transducer element associated with an acoustic adjustment layer is, the lower the sound velocity of the material of that acoustic adjustment layer is.

8. The ultrasound probe of claim 1 , wherein the acoustic adjustment layers are made of a material having an acoustic impedance which is either the same as, or close to, the acoustic impedance value of the acoustic lens.

9. The ultrasound probe of claim 1 , wherein the acoustic lens includes:

a first acoustic lens portion, of which the surface shape has a first curvature on a cross section which is parallel to the first direction and the transmission direction; and

a second acoustic lens portion which is arranged on the first acoustic lens portion in the transmission direction and of which the surface shape has a second curvature.

10. The ultrasound probe of claim 9 , wherein the second curvature is larger than the first curvature.

11. The ultrasound probe of claim 9 , wherein the first and second acoustic lens portions are made of the same material.

12. An ultrasound probe comprising:

an array of transducer elements in which a plurality of transducer elements are arranged two-dimensionally in a first direction corresponding to an elevation direction and in a second direction corresponding to the azimuth direction that is different from the first direction, wherein the array of transducer elements makes an interconversion between an electric pulse and an ultrasonic wave;

an acoustic lens which has a convex surface in a transmission direction of the ultrasonic wave on a cross section that is parallel to the first direction and the transmission direction and which converges ultrasonic waves transmitted from the plurality of transducer elements;

an acoustic adjustment layer which is made of a material that has a different sound velocity from the acoustic lens and which is arranged between one of the transducer elements of a row of the transducer elements arranged in the first direction and the acoustic lens, wherein both end surfaces in the first direction of the acoustic adjustment layer are arranged so as to substantially coincide with both end surfaces in the first direction of the one of the transducer elements, and no acoustic adjustment layer is arranged between at least some of the transducer elements of the row of transducer elements and the acoustic lens; and

an acoustic matching layer through which the ultrasonic waves transmitted from the plurality of transducer elements pass.