Method and device for driving capacitance transducer

Patent metadata

Field	Value
Publication number	US-10016788-B2
Application number	US-201414547884-A
Country	US
Kind code	B2
Filing date	Nov 19, 2014
Priority date	Nov 22, 2013
Publication date	Jul 10, 2018
Grant date	Jul 10, 2018

Abstract

Provided are a method, a device and the like for driving a capacitance transducer that enable reduction of transmission sound pressure variation caused by variation in characteristics of a capacitance transducer used for, e.g., an ultrasound conversion element. A method for driving a capacitance transducer including a plurality of elements each including cells each having a structure in which a vibration membrane including one electrode of a pair of electrodes formed with a cavity therebetween is supported in such a manner that the vibration membrane can vibrate is provided.

First claim

What is claimed is:

1. A method for driving a capacitance transducer including an element, the element including a cell having a structure in which a vibration membrane including one electrode of a pair of electrodes formed with a cavity therebetween is supported in such a manner that the vibration membrane can vibrate, the method comprising:
in a mode in which the element that receives acoustic waves, applying a voltage that is lower than a pull-in voltage to the element as a reception bias voltage; and
in a mode in which the element transmits an acoustic waves, applying a voltage that is lower than the reception bias voltage to the element as a transmission bias voltage,
wherein the transmission bias voltage is set to be not more than one half of the pull-in voltage.

2. The method for driving a capacitance transducer according to claim 1 , wherein the capacitance transducer includes a plurality of elements each including the cell.

3. The method for driving a capacitance transducer according to claim 2 , wherein variation of reception signals of the acoustic waves in each of the plurality of elements is less than a range of ±25% relative to an average reception signals of the acoustic waves.

4. The method for driving a capacitance transducer according to claim 1 , wherein an absolute value of an amplitude of a transmission drive voltage is set to be lower than the transmission bias voltage.

5. The method for driving a capacitance transducer according to claim 1 ,
wherein in the mode in which the element transmits the acoustic waves, a voltage obtained by superimposing a transmission drive voltage on the transmission bias voltage is applied to the element; and
wherein an absolute value of an amplitude of the transmission drive voltage is lower than a difference between the pull-in voltage and the transmission bias voltage.

6. The method for driving a capacitance transducer according to claim 5 , wherein a sum of the transmission bias voltage and the absolute value of the amplitude of the transmission drive voltage is set to be more than the reception bias voltage.

7. The method for driving a capacitance transducer according to claim 5 , wherein a waveform of the transmission drive voltage is a bipolar pulse.

8. The method for driving a capacitance transducer according to claim 5 , wherein the capacitance transducer performs transmission and reception of the acoustic waves by vibration of the vibration membrane including one electrode of the pair of electrodes, and
wherein a waveform of the transmission drive voltage applied to the electrode included in the vibration membrane is set to the waveform in which positive voltage is firstly applied and then negative voltage is applied in a condition that negative voltage is applied to the other electrode of the pair of electrodes.

9. A device for driving a capacitance transducer including an element, the element including a cell having a structure in which a vibration membrane including one electrode of a pair of electrodes formed with a cavity therebetween is supported in such a manner that the vibration membrane can vibrate,
the device comprising a voltage control unit that controls a voltage to be applied between the pair of electrodes,
wherein in a mode in which the element receives acoustic waves, the voltage control unit applies a voltage that is lower than a pull-in voltage as a reception bias voltage; and
wherein in a mode in which the element transmits acoustic waves, the voltage control unit applies a voltage that is lower than the reception bias voltage to the element as a transmission bias voltage,
wherein the transmission bias voltage is set to be not more than one half of the pull-in voltage.

10. A test object information obtaining apparatus comprising:
a capacitance transducer driven by a drive device according to claim 9 ; and
a processing unit that obtains information on a test object using an electric signal output from the capacitance transducer,
wherein the capacitance transducer receives acoustic waves from the test object and outputs the electric signal.

11. The device for driving a capacitance transducer according to claim 9 ,
wherein in the mode in which the element transmits the acoustic waves, the voltage control unit applies a voltage obtained by superimposing a transmission drive voltage on the transmission bias voltage to the element; and
wherein an absolute value of an amplitude of the transmission drive voltage is set to be lower than a difference between the pull-in voltage and the transmission bias voltage.

12. The device for driving a capacitance transducer according to claim 11 , wherein a sum of the transmission bias voltage and the absolute value of the amplitude of the transmission drive voltage is set to be more than the reception bias voltage.

13. The device for driving a capacitance transducer according to claim 11 , wherein a waveform of the transmission drive voltage is a bipolar pulse.

14. The device for driving a capacitance transducer according to claim 9 , wherein an absolute value of an amplitude of a transmission drive voltage is set to be lower than the transmission bias voltage.

15. The device for driving a capacitance transducer according to claim 14 , wherein the capacitance transducer performs transmission and reception of the acoustic waves by vibration of the vibration membrane including one electrode of the pair of electrodes, and
wherein an waveform of the transmission drive voltage applied to the electrode included in the vibration membrane is set to the waveform in which positive voltage is firstly applied and then negative voltage is applied in a condition that negative voltage is applied to the other electrode of the pair of electrodes.

16. The device for driving a capacitance transducer according to claim 9 , further comprising a switch unit that switches over between the transmission bias voltage in the mode in which the element transmits the acoustic waves and the reception bias voltage in the mode in which the element receives the acoustic waves,
wherein the switch unit performs switching so as to apply the transmission bias voltage from the voltage control unit to the element in driving for transmission, and to apply the reception bias voltage from the voltage control unit to the element in driving for reception.

17. The device for driving a capacitance transducer according to claim 9 , wherein the capacitance transducer includes a plurality of elements each including the cell.

18. The device for driving a capacitance transducer according to claim 17 , wherein variation of the acoustic waves which receives in each a plurality of elements is less than a range of ±25% relative to an average reception signals.

Assignees

• Canon Kk

Inventors

• Kato Ayako
• Torashima Kazutoshi

Classifications

• B06B1/0292 Primary

  Electrostatic transducers, e.g. electret-type · CPC title

• B06B1/0207

  Driving circuits (specially adapted for particular applications, see the relevant subclass, e.g. G01; circuits for steering transducer arrays G10K11/34; basic circuits H03) · CPC title

• B06B2201/20

  Application to multi-element transducer · CPC title