Ultrasound transducer manufactured by using micromachining process, its device, endoscopic ultrasound diagnosis system thereof, and method for controlling the same
An ultrasound transducer manufactured by using a micromachining process comprises: a first electrode into which a control signal for transmitting ultrasound is input; a substrate on which the first electrode is formed; a second electrode that is a ground electrode facing the first electrode with a prescribed space between the first and second electrodes; a membrane on which the second electrode is formed and which vibrates and generates the ultrasound when a voltage is applied between the first and second electrodes; a piezoelectric film contacting the membrane; and a third electrode electrically continuous to the piezoelectric film.
1. An ultrasound transducer device manufactured by using a micromachining process having an ultrasound transducer comprising:
a first electrode into which a control signal for transmitting ultrasound is input;
a substrate on which the first electrode is formed;
a second electrode that is a ground electrode facing the first electrode with a prescribed space between the first and second electrodes;
a membrane on which the second electrode is formed and which vibrates and generates the ultrasound when voltage is applied between the first and second electrodes;
a first piezoelectric film formed on the second electrode formed on a surface of the membrane; and
a third electrode that is connected to the first piezoelectric film and faces the second electrode via the piezoelectric film, said ultrasound transducer device comprising:
a conversion unit boosting an alternating current low voltage signal conveyed from a conveying cable, and converting it into a direct current voltage signal;
a first switching unit switching an electrical connection between the conversion unit and the first electrode;
a self oscillating unit performing self oscillation on the basis of the direct current voltage signal input into the first electrode in order to drive the ultrasound transducer to transmit ultrasound;
a reception signal processing unit performing a prescribed signal process on a reception signal created on the basis of the ultrasound received by the ultrasound transducer; and
a second switching unit switching an electrical connection between the conversion unit and the reception signal processing unit.
2. The ultrasound transducer according to claim 1 , wherein: the piezoelectric film is a piezoelectric material that does not contain lead.
3. The ultrasound transducer according to claim 2 , wherein: the piezoelectric material is one of aluminum nitride, zinc oxide, barium titanate, and barium strontium titanate.
4. The ultrasound transducer device according to claim 1 , wherein: the first switching unit and the second switching unit are respectively turned on and turned off when transmitting ultrasound, and are respectively turned off and turned on when receiving ultrasound.
5. The ultrasound transducer device according to claim 4 , wherein: the first switching unit and the second switching unit are a pair of electronic switches.
6. The ultrasound transducer device according to claim 5 , wherein: the first switching unit and the second switching unit are integrated on a surface of the substrate or in the substrate.
7. The ultrasound transducer device according to claim 1 , wherein: the ultrasound transducer further comprises:
a piezoelectric supporting member for supporting the membrane formed of a second piezoelectric film; and
a fourth electrode into which the direct current voltage signal for driving the piezoelectric supporting member is input.
8. The ultrasound transducer device according to claim 1 , wherein: the self oscillating unit:
is a positive feedback circuit including at least an amplification element for amplifying the feedback signal and the ultrasound transducer; and
inputs, into the amplification element as a feedback signal, a voltage signal generated from the first piezoelectric film corresponding to deformation of the membrane activated by applying the direct current voltage signal between the first electrode and the second electrode.
9. The ultrasound transducer device according to claim 8 , wherein: the self oscillating unit further comprises: a phase adjustment element for adjusting phases of the feedback signal in a stage earlier than the amplification element.
10. The ultrasound transducer device according to claim 8 , wherein: the self oscillating unit further comprises: a high-frequency wave removal unit removing a high-frequency wave corresponding to a high-order vibration mode.
11. The ultrasound transducer device according to claim 1 , wherein: the reception signal processing unit includes:
a charge amplification unit detecting the reception signal that is a charge signal;
an impedance conversion unit converting the reception signal having a high impedance into a reception signal having a low impedance; and
a voltage amplification unit amplifying the voltage of the reception signal.
12. The ultrasound transducer device according to claim 1 , wherein: the ultrasound transducer, the self oscillating unit, the reception signal processing unit, the first switching unit, and the second switching unit are integrated on the substrate.
13. An Endoscopic ultrasound diagnosis system including the ultrasound transducer device according to claim 1 .
14. The Endoscopic ultrasound diagnosis system according to claim 13 , wherein: the Endoscopic ultrasound diagnosis system is an ultrasound endoscope.
15. The Endoscopic ultrasound diagnosis system according to claim 13 , wherein: the ultrasound transducer device is used as a miniature ultrasound probe inserted into a forceps opening of an endoscope.
16. The Endoscopic ultrasound diagnosis system according to claim 13 , wherein: the ultrasound transducer device is used as an intravascular ultrasound probe.
17. The Endoscopic ultrasound diagnosis system according to claim 13 , wherein: the ultrasound transducer device is used as an ultrasound capsule endoscope.
18. A method of controlling an ultrasound transducer device manufactured by using a micromachining process, comprising:
an ultrasound transducer including:
a first electrode into which a control signal for transmitting ultrasound is input;
a substrate on which the first electrode is formed;
a second electrode that is a ground electrode facing the first electrode with a prescribed space between the first and second electrodes;
a membrane on which the second electrode is formed and which vibrates and generates ultrasound when voltage is applied between the first and second electrodes;
a first piezoelectric film formed on the second electrode formed on a surface of the membrane; and
a third electrode connected to the first piezoelectric film and facing the second electrode via the piezoelectric film; and
a conversion unit boosting an alternating current low-voltage signal conveyed from a conveying cable, and converting it into a direct current voltage signal;
a first switching unit switching an electrical connection between the conversion unit and the first electrode;
a self oscillating unit performing self-oscillation on the basis of the direct current voltage signal input into the first electrode in order to drive the ultrasound transducer to transmit ultrasound;
a reception signal processing unit performing a prescribed signal process on a reception signal created on the basis of the ultrasound received by the ultrasound transducer; and
a second switching unit switching an electrical connection between the conversion unit and the reception signal processing unit, wherein:
when transmitting ultrasound, the first switching unit is turned on and the second switching unit is turned off;
an alternating current voltage signal for controlling vibration of the membrane is boosted by the conversion unit in order to convert it into a direct current voltage signal;
the direct current voltage signal is supplied to the self oscillating unit via the first switching unit; and
ultrasound is transmitted from the ultrasound vibration on the basis of the self oscillating unit.
19. The method of controlling an ultrasound transducer device according to claim 18 , further comprising:
turning off the first switching unit and turning on the second switching unit when receiving ultrasound;
receiving ultrasound by the ultrasound transducer and converting the received ultrasound into an electric signal;
conveying the reception signal converted into the electric signal to the reception signal processing unit; and
amplifying the voltage of the reception signal by the reception signal processing unit, and performing impedance conversion.