Capacitive detection type electro-mechanical transducer

Patent metadata

Field	Value
Publication number	US-9594103-B2
Application number	US-201414296351-A
Country	US
Kind code	B2
Filing date	Jun 4, 2014
Priority date	Jan 12, 2010
Publication date	Mar 14, 2017
Grant date	Mar 14, 2017

Abstract

A capacitive detection type electro-mechanical transducer comprises; a cell formed by a first electrode arranged on a substrate and a second electrode arranged on a vibration film, and a detection circuit for detecting a displacement of the vibration film, based on a capacity change between the first and second electrodes, wherein a plurality of the cells are classified into a plurality of groups, each one includes at least two cells, and the first electrodes or the second electrodes of the cells of the same one group are commonly connected to the same one detection circuit, and an addition circuit for adding, into single information, signals from the plurality of detection circuits corresponding to the plurality of groups, and for outputting the information, and a capacitive load for each one of the detectors are formulated to be dispersedly arranged.

First claim

What is claimed is:

1. An apparatus comprising:
a plurality of cells, each cell including
(a) a first electrode, and
(b) a second electrode opposed to the first electrode with a gap between the first and second electrodes;
a plurality of detection circuits, each detection circuit being configured to detect a current output from a respective detection electrode that is one of the first and second electrodes; and
an addition circuit for adding signals from the plurality of detection circuits,
wherein the plurality of cells are classified into a plurality of groups, each group including at least two cells,
wherein a plurality of the detection electrodes of the cells in one group are commonly connected to one detection circuit of the plurality of detection circuits,
wherein the one detection circuit adds currents output from the plurality of the detection electrodes of the cells in one group and converts a current resulting from an addition of the currents output from the plurality of the detection electrodes of the cells in one group into a voltage,
wherein the addition circuit adds respective voltages converted by the plurality of the detection circuits,
wherein each detection circuit comprises a current-to-voltage conversion circuit including an operational amplifier, a feedback capacitance, and a feedback resistance, and
wherein, a gain bandwidth of the operational amplifier is GBW, a resistance value of the feedback resistance is RF, a capacitance value of the feedback capacitance is CF, a parasitic capacitance of an inverting input terminal of the operational amplifier is Cin, following Expression (1) is met:
C in≦π× GBW×R F ×( C F ) 2   Expression (1).

2. The apparatus according to claim 1 ,
wherein each detection circuit comprises a trans-impedance circuit including an operational amplifier, such that,
based on a predetermined frequency of the detection circuit, a predetermined feedback capacitance or resistance value of the trans-impedance circuit, a gain band width of the operational amplifier, a parasitic capacitance in the detection electrodes connected to the one detection circuit, and a parasitic capacitance in a wiring between the detection electrodes and the detection circuit,
a number of the plurality of detection circuits is determined.

3. The apparatus according to claim 1 , further comprising:
a first substrate provided such that the plurality of groups of the cells are arranged on one side of the first substrate, and the plurality of detection circuits are arranged on the other side of the first substrate opposite to the one side, and
a second substrate provided such that the addition circuit is arranged on the second substrate,
wherein each detection electrode is connected to an input terminal of the respective detection circuit through a wiring penetrating the first substrate, and
wherein an output terminal of each detection circuit is connected through a bump to an input terminal of the addition circuit.

4. The apparatus according to claim 1 , further comprising;
a first substrate provided such that the plurality of detection circuits are arranged on one side of the first substrate, and
a second substrate provided such that the addition circuit is arranged on the second substrate, and
wherein the plurality of groups of the cells are arranged on the detection circuits corresponding thereto so that the first electrode of each cell is arranged in opposition to the corresponding detection circuit,
wherein a respective output terminal of each detection circuit is connected through a wiring penetrating the first substrate to an electrode arranged on the other side of the first substrate opposite to the one side, and
wherein an input terminal of the addition circuit is connected through a bump to the electrode arranged on the other side of the first substrate.

5. The apparatus according to claim 1 , further comprising;
a first substrate provided such that the detection circuits and the addition circuit are arranged on one side of the first substrate,
wherein the plurality of groups of the cells are arranged two dimensionally on the detection circuits and the addition circuit,
wherein the first electrode of each cell is arranged in opposition to the corresponding detection circuit and the addition circuit.

6. The apparatus according to claim 1 ,
wherein each cell comprises a vibration film on which the second electrode is arranged.

7. The apparatus according to claim 1 ,
wherein the other electrode of the first and second electrodes, which is different from the detection electrode that is one of the first and second electrodes, is a bias electrode to which a bias voltage is applied.

8. The apparatus according to claim 1 ,
wherein each cell receives an ultrasonic wave, and
wherein an output from the addition circuit corresponds to information of the received ultrasonic wave in one pixel.

9. The apparatus according to claim 8 ,
wherein an image of an object is formed based on the output from the addition circuit.

10. The apparatus according to claim 1 ,
wherein each detection circuit and the corresponding one group are connected electrically though a wiring.

11. The apparatus according to claim 1 ,
wherein the plurality of cells are in one pixel and
wherein, when a capacitance parasitic to the plurality of the detection electrodes for one pixel is Cmut, a capacitance parasitic tone wiring connecting between the detection electrode and the current-to-voltage conversion circuit is Cwire and a number of the groups is N, following Expressions (2) and (3) are met:

Cin
=

Cmut
N

+
Cwire

Expression
⁢

⁢

(
2
)

N
≥

Cmut

π
×
GBW
×

R
F

×

(

C
F

)

2

-
Cwire

.

Expression
⁢

⁢

Assignees

• Canon Kk

Inventors

• Kandori Atsushi
• Takagi Makoto
• Majima Masao

Classifications

• G01N29/2406

  Electrostatic or capacitive probes, e.g. electret or cMUT-probes · CPC title

• B06B1/0292

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

• G01N29/2412

  using the magnetostrictive properties of the material to be examined, e.g. electromagnetic acoustic transducers [EMAT]; (investigating the presence of flaws using eddy currents G01N27/90, magnetostrictive transducers B06B1/08, measuring magnetostrictive properties G01R33/18) · CPC title

• B81C1/00246

  Monolithic integration, i.e. micromechanical structure and electronic processing unit are integrated on the same substrate · CPC title

• G01D5/24 Primary

  by varying capacitance · CPC title