Ultrasound probe and ultrasound diagnostic device using same
In order to obtain a high-resolution ultrasound diagnostic image while reducing the back side reflection of a ultrasound irradiated to the side opposite to the ultrasound transmission direction of an ultrasound transmission/reception device, disclosed is an ultrasound probe, wherein a substrate is provided thereon with a cavity, insulation layers having the cavity therebetween, and an upper layer electrode and a lower layer electrode having the cavity and the insulation layers therebetween, so as to form an ultrasound vibration element, the substrate is held by a backing with a low-modulus member therebetween, and a direct voltage and a alternating voltage are applied between the electrodes to vibrate the ultrasound vibration element, and wherein a mechanical impedance by the substrate and the low-modulus member has a substantially equal value as an acoustic impedance of the backing.
1. An ultrasound probe comprising an ultrasound vibration element composing a plurality of cells and a rim disposed between each of the cells, each of the cells constituted on a substrate by a cavity, by insulation layers with the cavity interposed therebetween, and by an upper layer electrode and a lower layer electrode with the cavity and the insulation layers interposed therebetween, the substrate being supported by a backing with a low-modulus member interposed therebetween, the ultrasound vibration element being vibrated by application of a direct-current voltage and an alternating current voltage between the electrodes;
wherein the backing has an acoustic impedance falling within ±1 MRayls (10 6 kg/m 2 s) of a mechanical impedance formed by the substrate and the low-modulus member.
2. The ultrasound probe according to claim 1 , wherein the rim is formed as a part of the insulation layers.
3. The ultrasound probe according to claim 2 , wherein portions of the insulation layers forming the rims protrude toward the substrate and are disposed above the cavity.
4. The ultrasound probe according to claim 1 , wherein the mechanical impedance is formed by the mass of the substrate and by a spring constant of the low-modulus member.
5. The ultrasound probe according to claim 1 , wherein, if Zx denotes the mechanical impedance formed by the mass of the substrate and by the spring constant of the low-modulus member and Zy represents the value of the acoustic impedance of the backing, then the values Zx and Zy are made to fall within ranges meeting the following three expressions:
Zx≤ 7.4 MRayls(106 kg/m2 s),
Zy≤ 8.3 MRayls(106 kg/m2 s), and
Zy≥ 0.883 Zx −0.532 MRayls(106 kg/m2 s).
6. The ultrasound probe according to claim 1 , wherein the substrate is a silicon substrate.
7. The ultrasound probe according to claim 5 , wherein the silicon substrate has a thickness of 50 μm or less.
8. The ultrasound probe according to claim 1 , wherein the backing on a long axis side thereof has a smaller thermal expansion coefficient than on a minor axis side thereof.
9. The ultrasound probe according to claim 1 , wherein the backing is a resin containing carbon fiber.
10. The ultrasound probe according to claim 9 , wherein the resin has added particles of silica or tungsten.
11. The ultrasound probe according to claim 1 , wherein approximately half the resonance frequency of mechanical vibrations of the substrate and the low-modulus member is set as the center frequency of ultrasonic drive.
12. An ultrasound diagnostic device comprising an ultrasound probe according to claim 1 for obtaining an ultrasound diagnostic image of a test object.