Capacitive micromachined ultrasonic transducer and information acquisition apparatus including capacitive micromachined ultrasonic transducer

Patent metadata

Field	Value
Publication number	US-10966682-B2
Application number	US-201615770427-A
Country	US
Kind code	B2
Filing date	Oct 12, 2016
Priority date	Oct 24, 2015
Publication date	Apr 6, 2021
Grant date	Apr 6, 2021

Abstract

A capacitive micromachined ultrasonic transducer having a wide reception band is provided.
The capacitive micromachined ultrasonic transducer includes an element including a first sub-element and a second sub-element each including a cell. The cell includes a vibrating membrane that includes one of two electrodes formed with a spacing therebetween and that is vibratably supported. The capacitive micromachined ultrasonic transducer further includes a first detection circuit, a second detection circuit, and a combining circuit that combines a signal from the first detection circuit and a signal from the second detection circuit. The first sub-element is electrically connected to the first detection circuit, and the second sub-element is electrically connected to the second detection circuit. The first detection circuit and the second detection circuit have different cut-off frequencies.

First claim

The invention claimed is:

1. A capacitive micromachined ultrasonic transducer comprising:
an element including a first sub-element and a second sub-element, the first sub-element including a plurality of first cells, the second sub-element including a plurality of second cells, the first cell including a first electrode and a first membrane, the first membrane including a second electrode, there being a space between the first membrane and the first electrode, the first membrane being vibratably supported, and the second cell including a first electrode and a second membrane, the second membrane including a second electrode, there being a space between the second membrane and the first electrode, the second membrane being vibratably supported;
a first detection circuit configured to generate a first signal generated by a change in capacitance between the first electrode and the second electrode of the first cell;
a second detection circuit configured to generate a second signal generated by a change in capacitance between the first electrode and the second electrode of the second cell; and
a combining circuit configured to combine the first signal and the second signal,
wherein the first sub-element is electrically connected to the first detection circuit,
wherein the second sub-element is electrically connected to the second detection circuit, and
wherein the first detection circuit and the second detection circuit have different cut-off frequencies, and
wherein the first sub-element and the second sub-element are disposed in a pattern of concentric circular rings or concentric polygonal rings, and
wherein the first sub-element is disposed inside the second sub-element.

2. The capacitive micromachined ultrasonic transducer according to claim 1 , wherein each of the first detection circuit and the second detection circuit includes a transimpedance circuit.

3. The capacitive micromachined ultrasonic transducer according to claim 1 , wherein the cut-off frequency of the first detection circuit is higher than the cut-off frequency of the second detection circuit.

4. The capacitive micromachined ultrasonic transducer according to claim 1 , wherein the first electrode of the first cell and the first electrode of the second cell are common, or the second electrode of the first cell and the second electrode of the second cell are common.

5. The capacitive micromachined ultrasonic transducer according to claim 1 , wherein a shape of the first cell is the same as a shape of the second cell.

6. The capacitive micromachined ultrasonic transducer according to claim 5 , wherein peak frequencies of output currents of the first sub-element and the second sub-element are between a cut-off frequency of the first detection circuit and a cut-off frequency of the second detection circuit, and
wherein number of the plurality of the first cells of the first sub-element is greater than number of the plurality of the second cells of the second sub-element.

7. The capacitive micromachined ultrasonic transducer according to claim 6 , wherein the number of the plurality of the first cells of the first sub element is in the range from 55% to 95% of the number of all the cells is within a range from 55% to 95% of a sum of the number of the plurality of the first cells and the number of the plurality of the second cells.

8. The capacitive micromachined ultrasonic transducer according to claim 5 , wherein each of peak frequencies of output currents of the first sub-element and the second sub-element is higher than each of the cut-off frequencies of the first detection circuit and the second detection circuit, and
wherein number of the plurality of the first cells of the first sub-element is the same as number of the plurality of the second cells of the second sub-element.

9. The capacitive micromachined ultrasonic transducer according to claim 8 , wherein the number of the plurality of the first cells is within a range from 25% to 75% of a sum of the number of the plurality of the first cells and the number of the plurality of the second cells.

10. The capacitive micromachined ultrasonic transducer according to claim 1 , wherein a ratio of a peak value of reception sensitivity of the first sub-element to a peak value of reception sensitivity of the second sub-element is 0.5 or greater and 0.9 or less.

11. The capacitive micromachined ultrasonic transducer according to claim 1 , wherein in at least one of the first sub-element and the second sub-element, a DC voltage is applied to one of the two electrodes, and an AC voltage is applied to the other electrode so that an acoustic wave is transmitted.

12. An information acquisition apparatus comprising:
the capacitive micromachined ultrasonic transducer according to claim 1 ;
a light source configured to emit a light beam; and
a processing unit,
wherein the capacitive micromachined ultrasonic transducer detects a photoacoustic wave generated due to the light beam emitted from the light source to a test object and outputs a detection signal, and
wherein the processing unit processes the detection signal and acquires information regarding the test object.

13. An information acquisition apparatus comprising:
the capacitive micromachined ultrasonic transducer according to claim 1 ; and
a processing unit,
wherein the capacitive micromachined ultrasonic transducer is capable of transmitting an ultrasonic wave,
wherein the capacitive micromachined ultrasonic transducer detects an acoustic wave generated by emission of the ultrasonic wave transmitted from the capacitive micromachined ultrasonic transducer to a test object and outputs a detection signal, and
wherein the processing unit processes the detection signal and acquires information regarding the test object.

14. The information acquisition apparatus according to claim 12 , wherein the capacitive micromachined ultrasonic transducer is capable of transmitting an ultrasonic wave, and
wherein the information acquisition apparatus further comprises a circuit unit configured to transmit and receive a signal between the capacitive micromachined ultrasonic transducer and the processing unit and a control unit configured to control the processing unit and the circuit unit.

15. The information acquisition apparatus according to claim 12 , wherein the processing unit processes the detection signal and acquires image information regarding the test object, and
wherein the information acquisition apparatus further comprises a display unit configured to display an image of the test object.

Assignees

• Canon Kk

Inventors

• Maruyama Ayako
• Torashima Kazutoshi
• Kandori Atsushi

Classifications

• B06B2201/51

  Electrostatic transducer · CPC title

• B06B1/0292

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

• A61B8/14

  Echo-tomography · CPC title

• A61B2562/028

  Microscale sensors, e.g. electromechanical sensors [MEMS] · CPC title

• G01S7/52079

  Constructional features (constructional features of transducers B06B; mounting transducers G10K11/00; constructional features of ultrasonic medical diagnostic devices A61B8/44) · CPC title