U.S. patent application number 11/666372 was filed with the patent office on 2007-12-27 for capacitive ultrasonic transducer and endo cavity ultrasonic diagnosis system using the same.
Invention is credited to Hideo Adachi, Tatsuo Kaimai, Yu Kondo, Akiko Mizunuma, Miyuki Murakami, Kiyoshi Nemoto, Atsushi Osawa, Kousei Tamiya, Katsuhiro Wakabayashi, Shinji Yasunaga.
Application Number | 20070299345 11/666372 |
Document ID | / |
Family ID | 36227711 |
Filed Date | 2007-12-27 |
United States Patent
Application |
20070299345 |
Kind Code |
A1 |
Adachi; Hideo ; et
al. |
December 27, 2007 |
Capacitive Ultrasonic Transducer and Endo Cavity Ultrasonic
Diagnosis System Using the Same
Abstract
A capacitive ultrasonic transducer (c-MUT) comprising a silicon
substrate and a transducer element which comprises transducer
cells, each of which is constituted by a first electrode equipped
on the top surface of the silicon substrate, a second electrode
placed opposite to the first electrode with a predetermined gap
therefrom and a membrane for supporting the second electrode,
wherein a trench is equipped between the adjacent transducers and a
conductive film is formed in the trench.
Inventors: |
Adachi; Hideo; (Iruma,
JP) ; Wakabayashi; Katsuhiro; (Tokyo, JP) ;
Mizunuma; Akiko; (Tokyo, JP) ; Osawa; Atsushi;
(Tokyo, JP) ; Kaimai; Tatsuo; (Tokyo, JP) ;
Yasunaga; Shinji; (Asaka, JP) ; Nemoto; Kiyoshi;
(Tokyo, JP) ; Murakami; Miyuki; (Tokyo, JP)
; Tamiya; Kousei; (Sagamihara, JP) ; Kondo;
Yu; (Yamato, JP) |
Correspondence
Address: |
SCULLY SCOTT MURPHY & PRESSER, PC
400 GARDEN CITY PLAZA
SUITE 300
GARDEN CITY
NY
11530
US
|
Family ID: |
36227711 |
Appl. No.: |
11/666372 |
Filed: |
October 20, 2005 |
PCT Filed: |
October 20, 2005 |
PCT NO: |
PCT/JP05/19336 |
371 Date: |
July 11, 2007 |
Current U.S.
Class: |
600/459 ;
29/594 |
Current CPC
Class: |
B06B 1/0292 20130101;
Y10T 29/49005 20150115; A61B 8/445 20130101; B06B 2201/76 20130101;
G10K 9/12 20130101; A61B 8/12 20130101 |
Class at
Publication: |
600/459 ;
029/594 |
International
Class: |
A61B 8/14 20060101
A61B008/14; H04R 31/00 20060101 H04R031/00 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 27, 2004 |
JP |
2004-312172 |
Jan 21, 2005 |
JP |
2005-014414 |
Jan 21, 2005 |
JP |
2005-014415 |
Claims
1. A capacitive ultrasonic transducer (c-MUT) comprising a silicon
substrate and a transducer element which comprises transducer
cells, each of which is constituted by a first electrode equipped
on the top surface of the silicon substrate, a second electrode
placed opposite to the first electrode with a predetermined gap
therefrom and a membrane for supporting the second electrode,
wherein a trench is equipped between the adjacent transducer
elements, a conductive film is formed in the trench, and the c-MUT
further comprises a flexible printed circuit board joined to the
back surface of the silicon substrate by way of electrode pads
placed on the back surface of the silicon substrate respectively
for the individual transducer elements.
2. (canceled)
3. The c-MUT according to claim 1, wherein a bottom of the trench
equipped between transducer units constituted by the transducer
elements, a plurality of which is one-dimensionally arrayed,
reaches at a surface of the flexible printed circuit by penetrating
the silicon substrate and electrode pad.
4. The c-MUT according to claim 1, wherein the conductive film is
formed on a trench interior wall and bottom of the trench and the
conductive film formed on the bottom is joined to an Ohmic contact
zone which is featured on the silicon substrate surface.
5. The c-MUT according to claim 1, wherein the trench is filled
with an ultrasonic attenuation material.
6. The c-MUT according to claim 5, wherein the ultrasonic
attenuation material is a composite resin mixing a fine tungsten
powder with a resin of which the main component is at least either
one of epoxy resin, silicone resin, or urethane resin.
7. The c-MUT according to claim 1, wherein a cross-sectional form
of the trench is a taper form in which a trench width is decreased
with the depth of the trench.
8. The c-MUT according to claim 1, wherein the inside wall of the
trench is featured with a surface irregularity of no less than an
order of a sub-micrometer.
9. The c-MUT according to claim 3, wherein the penetrating trench
surface is covered with the conductive film and is connected to a
ground wire equipped on the flexible printed circuit by way of a
conductive adhesive, ball bump or anisotropic dielectrics film.
10. The c-MUT according to claim 1, wherein the trench has a curve
form or saw-tooth form, at least other than a straight line form
when viewing the transducer element from the above.
11. A production method for a capacitive ultrasonic transducer
(c-MUT) comprising a silicon substrate and a transducer element
which comprises transducer cells, each of which is constituted by a
first electrode equipped on the top surface of the silicon
substrate, a second electrode placed opposite to the first
electrode with a predetermined gap therefrom and a membrane for
supporting the second electrode, comprising: a trench forming
process for equipping in between the adjacent transducer elements
with a trench; and a conductivity forming process for forming a
third electrode on a bottom of the trench by making it
conductive.
12. The production method for a c-MUT according to claim 11,
wherein the conductivity forming process applies an ion
implantation or chemical vapor deposition method, followed by
applying an expansion process, thereby forming the third
electrode.
13. The production method for a c-MUT according to claim 11,
wherein the conductivity forming process forms the third electrode
by a physical vapor deposition.
14. The production method for a c-MUT according to claim 11,
further comprising an ultrasonic attenuation material filling
process for filling the trench, in which the third electrode is
formed, with an ultrasonic attenuation material.
15. The production method for a c-MUT according to claim 14,
further comprising a first cutting process for cutting the trench
filled with the ultrasonic attenuation material.
16. The production method for a c-MUT according to claim 11,
comprising a second cutting process for cutting the trench by
cutting through the silicon substrate and electrode pad and
reaching at a surface of the flexible printed circuit.
17. The production method for a c-MUT according to claim 15,
wherein the first cutting process cuts by using a laser beam.
18. The production method for a c-MUT according to claim 16,
wherein the second cutting process cuts by using a laser beam.
19. An ultrasonic endoscope comprising the c-MUT according to claim
1.
20. An endo cavity ultrasonic endoscopic diagnosis system,
comprising: an ultrasonic endoscopic scope equipped with a
capacitive ultrasonic transducer (c-MUT) for transmitting and
receiving an ultrasound; a transducer state discernment unit for
discerning a state of the c-MUT; and an image construction unit for
constructing an ultrasonic diagnosis image from sensed information
sensed by the c-MUT according to the state discerned by the
transducer state discernment unit.
21. The endo cavity ultrasonic endoscopic diagnosis system
according to claim 20, wherein the transducer state discernment
unit comprises a state detection unit for detecting a state of the
c-MUT either of being on the outside of a body and moving within an
endo cavity until reaching an inside wall of the endo cavity, or
that of reaching a target diagnosis region, and a detection
information discernment unit for discerning the state based on
detection information obtained from the state detection unit.
22. The endo cavity ultrasonic endoscopic diagnosis system
according to claim 20, further comprising: a storage unit for
storing the sensed information, and a storage control unit for
having the storage unit, which corresponds to a discernment result,
store the sensed information based on the discernment result by the
transducer state discernment unit.
23. The endo cavity ultrasonic endoscopic diagnosis system
according to claim 21, wherein the state detection unit is an
optical sensor equipped approximately in the neighborhood of the
c-MUT, and the detection information discernment unit discerns a
state of the c-MUT either of being on the outside of a body,
reaching an endo cavity and yet not touching an inside wall
thereof, or contacting therewith based on an output of the optical
sensor.
24. The endo cavity ultrasonic endoscopic diagnosis system
according to claim 21, wherein the state detection unit is a
pressure sensor equipped approximately in the neighborhood of the
c-MUT, and the detection information discernment unit discerns a
state of the c-MUT either of being on the outside of a body,
reaching an endo cavity and yet not touching an inside wall
thereof, or contacting therewith based on an output of the pressure
sensor.
25. The endo cavity ultrasonic endoscopic diagnosis system
according to claim 21, wherein the state detection unit generates
the detection information corresponding to an electric signal
expressing the sensed information, and detection information
discernment unit discerns a state of the c-MUT either of being on
the outside of a body, reaching an endo cavity and yet not touching
an inside wall thereof, or contacting therewith based on the state
detection information.
26. The endo cavity ultrasonic endoscopic diagnosis system
according to claim 25, wherein a state detection unit is a filter
circuit letting the electric signal pass if a frequency thereof is
equal to or less than a predefined threshold value.
27. An endo cavity ultrasonic endoscopic diagnosis system,
comprising: an ultrasonic endoscope equipped with a capacitive
ultrasonic transducer (c-MUT) for transmitting and receiving an
ultrasound; a transducer state discernment unit for discerning a
state of the c-MUT; a storage unit for storing sensed information
sensed by the c-MUT; a storage control unit for having the storage
unit, which corresponds to a discernment result, store the sensed
information based on the discernment result by the transducer state
discernment unit; an arithmetic operation unit for performing an
arithmetic operation process based on at least one piece of the
sensed information among the sensed information stored in the
storage unit; and an image construction unit for constructing an
ultrasonic diagnosis image from an arithmetic operation result of
the operation process performed by the arithmetic operation
unit.
28. The endo cavity ultrasonic endoscopic diagnosis system
according to claim 27, wherein the c-MUT is a one-dimensional or
two-dimensional array type C-MUT which is constituted by a
plurality of c-MUT elements and which arrays the plurality thereof
on an outer circumference of a cylinder.
29. The endo cavity ultrasonic endoscopic diagnosis system
according to claim 28, wherein a trench is featured in between the
adjacent transducer elements.
30. The endo cavity ultrasonic endoscopic diagnosis system
according to claim 29, wherein a conductive film is formed in the
trench.
31. The endo cavity ultrasonic endoscopic diagnosis system
according to claim 28, further comprising a radial scan control
unit for making a compound ultrasonic beam, which is transmitted
from the c-MUT, perform a radial scan along a circumferential
direction of the cylinder.
32. The endo cavity ultrasonic endoscopic diagnosis system
according to claim 31, wherein the radial scan control unit makes
the compound ultrasonic beam perform a sector scan in the
longitudinal axis direction of the cylinder.
33. The endo cavity ultrasonic endoscopic diagnosis system
according to claim 27, wherein the arithmetic operation unit
performs an arithmetic operation for calculating a sum, difference
or correlation of at least two pieces of the sensed information
among the sensed information stored in the storage unit.
34. The endo cavity ultrasonic endoscopic diagnosis system
according to claim 27, wherein the arithmetic operation unit
performs an arithmetic operation for calculating an autocorrelation
from one piece of the sensed information.
35. The endo cavity ultrasonic endoscopic diagnosis system
according to claim 27, wherein the transducer state discernment
unit comprises a state detection unit for detecting a state of the
c-MUT either of being on the outside of a body and moving within an
endo cavity until reaching an inside wall of the endo cavity, or
that of reaching a target diagnosis region, and a detection
information discernment unit for discerning the state based on
detection information obtained from the state detection unit.
36. The endo cavity ultrasonic endoscopic diagnosis system
according to claim 35, wherein the state detection unit is an
optical sensor equipped approximately in the neighborhood of the
c-MUT, and the detection information discernment unit discerns a
state of the c-MUT either of being on the outside of a body,
reaching an endo cavity and yet not touching an inside wall
thereof, or contacting therewith based on an output of the optical
sensor.
37. The endo cavity ultrasonic endoscopic diagnosis system
according to claim 35, wherein the state detection unit is a
pressure sensor equipped approximately in the neighborhood of the
c-MUT, and the detection information discernment unit discerns a
state of the c-MUT either of being on the outside of a body,
reaching an endo cavity and yet not touching an inside wall
thereof, or contacting therewith based on an output of the pressure
sensor.
38. The endo cavity ultrasonic endoscopic diagnosis system
according to claim 35, wherein the state detection unit generates
the detection information corresponding to an electric signal
expressing the sensed information, and detection information
discernment unit discerns a state of the c-MUT either of being on
the outside of a body, reaching an endo cavity and yet not touching
an inside wall thereof, or contacting therewith based on the state
detection information.
39. The endo cavity ultrasonic endoscopic diagnosis system
according to claim 38, wherein a state detection unit is a filter
circuit letting the electric signal pass if a frequency thereof is
equal to or less than a predefined threshold value.
40. The endo cavity ultrasonic endoscopic diagnosis system
according to claim 27, wherein the storage control unit stores at
least one piece of the sensed information among pieces thereof
which is sensed in a state of the c-MUT either of being on the
outside of a body, reaching an endo cavity and yet not touching an
inside wall thereof, or contacting therewith.
41. The endo cavity ultrasonic endoscopic diagnosis system
according to claim 27, wherein the sensed information stored in a
first storage unit among the storage unit is first sensed
information sensed by making the c-MUT transmit an ultrasound under
a condition of the ultrasound not reflecting.
42. The endo cavity ultrasonic endoscopic diagnosis system
according to claim 41, wherein the sensed information stored in a
second storage unit among the storage unit is second sensed
information sensed by the c-MUT transmitting and receiving an
ultrasound in a state of being in an endo cavity and yet not
touching an inside wall thereof, and the arithmetic operation unit
calculates a correlation or difference between the second sensed
information and first sensed information.
43. The endo cavity ultrasonic endoscopic diagnosis system
according to claim 41, wherein the sensed information stored in a
third storage unit among the storage unit is third sensed
information sensed by the c-MUT transmitting and receiving an
ultrasound in a state of touching an inside wall of an endo cavity,
and the arithmetic operation unit calculates a correlation or
difference between the third sensed information and first sensed
information.
44. The endo cavity ultrasonic endoscopic diagnosis system
according to claim 41, wherein the sensed information stored in a
second storage unit among the storage unit is second sensed
information sensed by the c-MUT transmitting and receiving an
ultrasound in a state of being in an endo cavity and yet not
touching an inside wall thereof, the sensed information stored in a
third storage unit among the storage unit is third sensed
information sensed by the c-MUT transmitting and receiving an
ultrasound in a state thereof touching an inside wall of an endo
cavity, and the arithmetic operation unit performs a first
arithmetic operation for calculating a correlation or difference
between the second sensed information and first sensed information;
a second arithmetic operation for calculating a correlation or
difference between the third sensed information and first sensed
information; and adds the results of the first and second
arithmetic operations.
45. The endo cavity ultrasonic endoscopic diagnosis system
according to claim 42, wherein said ultrasonic diagnosis image is
an image expressing a contour of an inside wall surface of an endo
cavity.
46. The endo cavity ultrasonic endoscopic diagnosis system
according to claim 43, wherein said ultrasonic diagnosis image is
an image expressing a tomography of an organization of an endo
cavity.
47. The endo cavity ultrasonic endoscopic diagnosis system
according to claim 44, wherein said ultrasonic diagnosis image is
an image expressing a contour of an inside wall surface of an endo
cavity and one expressing a tomography of an organization
thereof.
48. A noise elimination apparatus for eliminating a noise component
from sensed information sensed by a capacitive ultrasonic
transducer (c-MUT) used for an endo cavity ultrasonic endoscopic
diagnosis system comprising an ultrasonic endoscopic scope equipped
with the c-MUT for transmitting and receiving an ultrasound,
comprising: a first storage unit for storing the first sensed
information sensed by making the c-MUT transmit an ultrasound under
a condition of the ultrasound not reflecting; a second storage unit
for storing the second sensed information sensed by the c-MUT
transmitting and receiving an ultrasound under a condition thereof
in a state of being in the inside of an endo cavity and yet not
touching an inside wall thereof; and an arithmetic operation unit
for calculating a correlation or difference between the second
sensed information and first sensed information.
49. A noise elimination apparatus for eliminating a noise component
from sensed information sensed by a capacitive ultrasonic
transducer (c-MUT) used for an endo cavity ultrasonic endoscopic
diagnosis system comprising an ultrasonic endoscopic scope equipped
with the c-MUT for transmitting and receiving an ultrasound,
comprising: a first storage unit for storing the first sensed
information sensed by making the c-MUT transmit an ultrasound under
a condition of the ultrasound not reflecting; a third storage unit
for storing the third sensed information sensed by the c-MUT
transmitting and receiving an ultrasound under a condition thereof
touching an inside wall of an endo cavity; and an arithmetic
operation unit for calculating a correlation or difference between
the third sensed information and first sensed information.
50. A noise elimination method for eliminating a noise component
from sensed information sensed by a capacitive ultrasonic
transducer (c-MUT) used for an endo cavity ultrasonic endoscopic
diagnosis system comprising an ultrasonic endoscopic scope equipped
with the c-MUT for transmitting and receiving an ultrasound,
comprising: obtaining the first sensed information sensed by making
the c-MUT transmit an ultrasound under a condition of the
ultrasound not reflecting; obtaining the second sensed information
sensed by the c-MUT transmitting and receiving an ultrasound under
a condition thereof in a state of being in the inside of an endo
cavity and yet not touching an inside wall thereof; and calculating
a correlation or difference between the second sensed information
and first sensed information.
51. A noise elimination method for eliminating a noise component
from sensed information sensed by a capacitive ultrasonic
transducer (c-MUT) used for an endo cavity ultrasonic endoscopic
diagnosis system comprising an ultrasonic endoscopic scope equipped
with the c-MUT for transmitting and receiving an ultrasound,
comprising: obtaining the first sensed information sensed by making
the c-MUT transmit an ultrasound under a condition of the
ultrasound not reflecting; obtaining the third sensed information
sensed by the c-MUT transmitting and receiving an ultrasound under
a condition thereof touching an inside wall of an endo cavity; and
calculating a correlation or difference between the third sensed
information and first sensed information.
Description
TECHNICAL FIELD
[0001] The present invention relates to a capacitive micromachined
ultrasonic transducer (c-MUT) produced using silicon process and an
endoscopic ultrasonic diagnostic system including c-MUT.
BACKGROUND ART
[0002] An ultrasonic diagnosis method for transmitting an
ultrasound to an endo cavity wall and diagnosing by imaging the
body tissue using an echo signal from body tissue targets has
become widely used. One of the equipment used for the ultrasonic
diagnosis method is an ultrasonic endoscope. The ultrasonic
endoscope is equipped with an ultrasonic transducer at the head
part of an insertion tube which is for inserting into an endo
cavity. The transducer is configured to transmit an ultrasound into
an endo cavity by converting an electric signal into an ultrasound,
receive an ultrasound which is reflected from the body tissue and
convert it into an electric signal.
[0003] A conventional ultrasonic transducer has been using a
ceramic lead zirconate titanate (PZT) as a piezoelectric element
for converting an electric signal into an ultrasound. However,
attention is recently focused on a capacitive micromachined
ultrasonic transducer (abbreviated as "c-MUT" hereinafter) produced
by processing a silicon semiconductor substrate by means of a
silicon micromachining technique. This is one of devices generally
called a micromachine (i.e., Micro Electro-Mechanical System:
MEMS).
[0004] A MEMS device is formed on a silicon substrate or glass
substrate as a miniature structure which is an electrically and
mechanically combined component sometimes accompanied with driving
integral circuit, such as a transducer for outputting a mechanical
force, a driving mechanism for driving the transducer and a
semiconductor integrated circuit for controlling the driving
mechanism. The basic characteristic of the MEMS device lies in
integrating the transducer, which is configured as a mechanical
structure, of a part of the device, and driving the transducer
electrically by applying a Coulomb attraction between
electrodes.
[0005] Meanwhile, a non-patent document 1 has disclosed a c-MUT as
shown in FIG. 1. FIG. 1(a) shows the top face of two sets of a
single-dimensional c-MUT array consisting of 64 pieces of elements;
FIG. 1(b) shows a singularized one piece of c-MUT element equipped
with dummy neighbors; and FIG. 1(c) shows an enlarged diagram of a
c-MUT element structured by parallelly connected by 8.times.160
pieces of cells.
[0006] The c-MUT element 150 comprises a plurality of cells 151,
upper electrodes 152 equipped on the upper parts of individual
cells, ground electrodes 153, dummy neighbors 155 and trenches 156.
The upper electrodes 152 are connected to one another and they are
connected to the electrodes 153 on the ends. The dummy neighbors
155 are for preventing a crosstalk with the adjacent elements. A
trench 156 is equipped between the electrode 153 and dummy neighbor
155.
[0007] The upper electrodes are supported by a membrane. Bottom
electrodes (not shown herein) are equipped at a position opposite
to the upper electrodes 152 within the cells, and there is a cavity
between the bottom electrode and the membrane.
[0008] As a voltage is applied to the upper and bottom electrodes
of the element, each cell is simultaneously driven to vibrate
concurrently in the same phase, thereby transmitting an
ultrasound.
[0009] The non-patent document 1 documents a finding that a Lamb
wave (i.e., A0 mode) and a Stoneley wave (i.e., a boundary wave)
transmitting between the solid phase and fluid phase give a great
influence on a crosstalk between the elements.
[0010] FIG. 2 shows a vibrational wave occurring in a membrane 160
in the case of generating an ultrasound by using the c-MUT shown in
FIG. 1. FIG. 2 is a cross-sectional diagram of the element shown in
FIG. 1. If there are distinctive end parts 161 by equipping the
trenches 156 on both ends, as in the element 150, a standing wave
162 is generated with the end parts 161 as nodes.
[0011] That is, a standing wave is generated between a pair of
walls existing apart from each other by a frequency which is
determined by the distance between the walls and by the transverse
sonic velocity of a material (i.e., silicon in the configuration of
FIG. 2) filling therebetween. Considering a pair of adjacent
trenches, an vibrational wave excited on a membrane is first
transmitted along the surface of the membrane as a Lamb wave or
Stoneley wave. Then an ultrasound, that is the vibrational wave, is
multiply reflected by the right side wall on the left side trench
and left side wall of the right side trench, becoming possibly a
transverse standing wave. The transverse standing wave becomes an
vibrational wave with a base having a frequency component of which
a distance L is 1/2.lamda. overlapped with a high-order standing
wave of the base. Therefore, the existence of such a pair of walls
generates a standing wave. The standing wave 162 is possible to
become a noise component in an transducing of an ultrasound.
[0012] Non-patent document 1: Xuecheng Jin, et al (3),
"Characterization of One-Dimensional Capacitive Micromachined
Ultrasonic Immersion Transducer Arrays", in "IEEE Transactions on
Ultrasonic, Ferroelectrics and Frequency Control", Vol. 48, NO. 3,
P 750-760, May 2001
[0013] Non-patent document 2: A. G. Bashford, et al (2),
"Micromachined Ultrasonic Capacitance Transducers for Immersion
Applications", in "IEEE Transactions on Ultrasonic, Ferroelectrics
and Frequency Control", Vol. 45, No. 2, March (1998), P.
367-375
DISCLOSURE OF INVENTION
[0014] A capacitive ultrasonic transducer (c-MUT) according to the
present invention is one comprising a silicon substrate and a
transducer element which comprises transducer cells, each of which
is constituted by a first electrode equipped on the top surface of
the silicon substrate, a second electrode placed opposite to the
first electrode with a predetermined gap therefrom and a membrane
for supporting the second electrode, wherein a trench is equipped
between the adjacent transducer elements and a conductive film is
formed in the trench.
[0015] A production method for a c-MUT comprising a silicon
substrate and a transducer element which comprises transducer
cells, each of which is constituted by a first electrode equipped
on the top surface of the silicon substrate, a second electrode
placed opposite to the first electrode with a predetermined gap
therefrom and a membrane for supporting the second electrode
according to the present invention comprises: a trench forming
process for equipping in between the adjacent transducer elements
with a trench; and a conductivity forming process for forming a
third electrode on a bottom of the trench by making it
conductive.
[0016] An endo cavity ultrasonic endoscopic diagnosis system
according to the present invention comprises: an ultrasonic
endoscopic scope equipped with a c-MUT for transmitting and
receiving an ultrasound; a transducer state discernment unit for
discerning such a wrong state of the c-MUT as an electrical short;
and an image construction unit for constructing an ultrasonic
diagnosis image from sensed information sensed by the c-MUT
according to the state discerned by the transducer state
discernment unit.
[0017] An endo cavity ultrasonic endoscopic diagnosis system
according to the present invention comprises: an ultrasonic
endoscope equipped with a c-MUT for transmitting and receiving an
ultrasound; a transducer state discernment unit for discerning a
state of the c-MUT; a storage unit for storing information sensed
by the c-MUT; a storage control unit for having the storage unit,
which corresponds to a discernment result, store the information
based on the discernment result by the transducer state discernment
unit; an arithmetic operation unit for performing an arithmetic
operation process based on at least one piece of the information
among the information stored in the storage unit; and an image
construction unit for constructing an ultrasonic diagnosis image
from an arithmetic operation result of the operation process
performed by the arithmetic operation unit.
[0018] A noise elimination apparatus for eliminating a noise
component from information sensed by a c-MUT used for an endo
cavity ultrasonic endoscopic diagnosis system comprising an
ultrasonic endoscopic scope equipped with the c-MUT for
transmitting and receiving an ultrasound according to the present
invention comprises: a first storage unit for storing the first
information sensed by making the c-MUT transmit an ultrasound under
a condition of the ultrasound not reflecting; a second storage unit
for storing the second information sensed by the C-MUT transmitting
and receiving an ultrasound under a condition thereof in a state of
being in the inside of an endo cavity and yet not touching an
inside wall thereof; and an arithmetic operation unit for
calculating a correlation or difference between the second
information and first information.
BRIEF DESCRIPTION OF DRAWINGS
[0019] FIG. 1 is a diagram showing a conventional c-MUT;
[0020] FIG. 2 is a diagram showing a situation of generating a
standing wave in a membrane in the case of using the c-MUT shown in
FIG. 1;
[0021] FIG. 3 is a diagram showing a radial scanning ultrasonic
transducer according to a first-1 embodiment;
[0022] FIG. 4 is a diagram showing a top view of a single body of a
transducer unit according to the first-1 embodiment;
[0023] FIG. 5 is a diagram showing a top view of a single body of a
transducer element according to the first-1 embodiment;
[0024] FIG. 6 is a diagram of cross-section Aa-Ab of FIG. 5;
[0025] FIG. 7A is a diagram showing a production process of a c-MUT
according to the first-1 embodiment (part 1);
[0026] FIG. 7B is a diagram showing a production process of a c-MUT
according to the first-1 embodiment (part 2);
[0027] FIG. 7C is a diagram showing a production process of a c-MUT
according to the first-1 embodiment (part 3);
[0028] FIG. 8 is a diagram exemplifying a variation of a trench
form according to the first-2 embodiment (part 1);
[0029] FIG. 9 is a diagram exemplifying a variation of a trench
form according to the first-2 embodiment (part 2);
[0030] FIG. 10 is a diagram exemplifying a variation of a trench
form according to the first-2 embodiment (part 3);
[0031] FIG. 11 is a diagram exemplifying a variation of a c-MUT
element according to the first-3 embodiment (part 1);
[0032] FIG. 12 is a diagram exemplifying a variation of a c-MUT
element according to the first-3 embodiment (part 2);
[0033] FIG. 13 is a diagram exemplifying a variation of a c-MUT
element according to the first-3 embodiment (part 3);
[0034] FIG. 14 is a diagram exemplifying a variation of a c-MUT
element according to the first-3 embodiment (part 4);
[0035] FIG. 15 is a diagram exemplifying a variation of a c-MUT
element according to the first-3 embodiment (part 5);
[0036] FIG. 16A is a diagram exemplifying the case of forming a
trench of a curved line when viewing the transducer element
according to the first-3 embodiment from above;
[0037] FIG. 16B is a diagram exemplifying the case of forming a
trench of a curved line when viewing the transducer element
according to the first-3 embodiment from above;
[0038] FIG. 16C is a diagram exemplifying the case of forming a
trench of a curved line when viewing the transducer element
according to the first-3 embodiment from above;
[0039] FIG. 17 is a diagram showing an outline of an endo cavity
ultrasonic diagnosis system according to a second embodiment;
[0040] FIG. 18 is a diagram showing an external configuration of an
ultrasonic endoscopic scope according to the present embodiment of
the second embodiment;
[0041] FIG. 19 is a diagram showing a comprisal of a capacitive
radial and sector scanning array ultrasonic transducer according to
the second embodiment;
[0042] FIG. 20 is a diagram showing an ultrasonic anechoic cell
according to the second embodiment;
[0043] FIG. 21A is a diagram showing the case of inserting, into an
endo cavity (i.e., in the state of inserting into a mouth), an
ultrasonic transducer according to the second embodiment;
[0044] FIG. 21B is a diagram showing the case of inserting, into an
endo cavity (i.e., in the states of contacting an ultrasonic
transducer with the inside wall of a stomach and
transmitting/receiving an ultrasound), an ultrasonic transducer
according to the second embodiment;
[0045] FIG. 22 is a diagram showing an outline of an internal
comprisal of an endo cavity ultrasonic diagnosis system according
to the second embodiment;
[0046] FIG. 23 is a diagram showing a frequency characteristic when
a target object is contacting and not contacting with an ultrasonic
transducer according to a third embodiment;
[0047] FIG. 24 is a diagram showing an outline of an internal
comprisal of an endo cavity ultrasonic diagnosis system according
to the third embodiment; and
[0048] FIG. 25 is a diagram showing an arithmetic operation control
circuit for performing a signal process of a plurality of patterns
according to a fourth embodiment.
BEST MODE FOR CARRYING OUT THE INVENTION
[0049] However, the equipment of the trench 156, dummy neighbor 155
and electrode zone 153 between the trench 156 and cell zone for
transmitting and receiving an ultrasound, as in the transducer
element 150, makes a ratio of the transducer zone to the entirety
of the transducer element small.
[0050] If the area size of the cell zone is desired to maintain at
a certain size in this case, the transducer element needs to be
enlarged, resulting in negating a possibility of miniaturizing an
ultrasonic transducer employing the c-MUT. If the size of the
element is attempted to maintain a similar size as before, on the
other hand, requiring the area size of the cell zone to be smaller,
resulting in decreasing a generated output of ultrasounds.
[0051] A preferred embodiment of the present invention is to
provide a c-MUT not allowing a decrease of an area size ratio of a
cell zone to the entirety of the c-MUT equipped with trenches
respectively on both ends of a transducer element, and a reduced
output of a generated ultrasound.
[0052] Incidentally, if a conventional piezoelectric transducer is
operated in the air, there is a possibility of a breakdown or rapid
deterioration of a characteristic occurring, and therefore an
operation in the air has been avoided. This has conventionally
limited a use of the ultrasonic endoscopic scope only in the state
of contacting with an inside wall of an endo cavity. Likewise, it
is unable to transmit an ultrasound in the air, hence precluding a
detection of a noise signal stemming only from a transducer.
[0053] Also, a detection of an aerial sonic wave has been
conventionally impossible by the same structure as a piezoelectric
transducer of a type to be contacting with an endo cavity wall
because there is a large difference in acoustic impedance between a
live tissue and air.
[0054] Due to this, there has not conventionally been necessary to
detect information related to a state of an ultrasonic transducer
as to whether or not it contacts with an endo cavity wall.
[0055] In the case of using an ultrasonic transducer capable of
transmitting and receiving an ultrasound (called as "aerial
ultrasound") in the state of the ultrasonic transducer not touching
with an endo cavity wall, however, a detection of information
related to a state of whether or not the ultrasonic transducer
touching an endo cavity wall becomes necessary.
[0056] A preferred embodiment of the present invention accordingly
provides an endo cavity ultrasonic diagnosis system which detects
information related to a state of whether or not the ultrasonic
transducer touching an endo cavity wall.
[0057] Meanwhile, there has conventionally been no endo cavity
ultrasonic diagnosis system existing to obtain an ultrasonic
diagnosis image which is picked up with an ultrasonic transducer
touching an endo cavity wall and one which is picked up with the
transducer not touching the endo cavity wall by using the same
transducer.
[0058] Next, the technique disclosed in the non-patent document 1
equips trenches respectively on both ends of a transducer element,
thereby suppressing a crosstalk between elements, as noted above.
The equipment of such trenches, however, has been faced with the
problem of generating a noise caused by a standing wave when using
an element equipped with the trenches respectively on both ends as
described for FIG. 2.
[0059] Another preferred embodiment of the present invention
accordingly provides an endo cavity ultrasonic diagnosis system
which builds up an ultrasonic diagnosis image related to an
asperity of an endo cavity wall while inserting, into the endo
cavity, an ultrasonic endoscopic scope equipped with the same c-MUT
regardless of it contacting the endo cavity wall, and which also
builds up an ultrasonic diagnosis image related to a fault by being
stationary held in contact with the endo cavity wall when reaching
a diagnosis region, with a noise component being removed from the
thusly buildup ultrasonic diagnosis images.
[0060] Now, the following is a description on the preferred
embodiment of the present invention.
First Embodiment
The First-1 Embodiment
[0061] The present embodiment describes a production of a
transducer element equipped with a ground electrode on the bottom
of a trench.
[0062] FIG. 3 shows a capacitive radial scanning array ultrasonic
transducer according to the present embodiment. The radial scanning
ultrasonic transducer 1 comprises a transducer unit 2 constituted
by a plurality of transducer elements 3, by a control circuit unit
4 and by a flexible print circuit board (FPC) 5 for
interconnection.
[0063] A plurality of rectangular transducer units 2 is serially
connected in a short direction thereof, resulting in featuring a
cylindrical form. The FPC 5 is featured with a wiring pattern and
electrode pads on the FPC. The control circuit unit 4 is placed, as
one control circuit for one transducer unit, on the reverse side of
the c-MUT vis-a-vis the FPC 5 and in equi-position with the
transducer unit 2. The control circuit unit 4, being equipped on
the rear surface of the transducer unit 2 (i.e., on the internal
circumference of the cylindrical form), is configured for
controlling an exchange of electrical signals to and from the
transducer units 2. A through hole penetrating the FPC is featured
for an element of the c-MUT as unit, and is placed so as to connect
the c-MUT unit to control circuit unit via the through hole. The
control circuit unit 4 is constituted by an integrated circuit such
as a pulser, charge amplifier and multiplexer, or by such
component. Note that the form of the transducer unit 2 is not
limited to a rectangle.
[0064] FIG. 4 shows a top view of a single body of the transducer
unit 2 according to the present embodiment. The transducer unit 2
is constituted by a plurality of square transducer elements 3. The
transducer unit 2 shown in FIG. 4 is configured by arraying a
plurality of transducer elements 3 in one dimension. In between the
adjacent transducer units is featured with a trench 7 (i.e., trench
formed along an array direction of transducer unit) penetrating
until the FPC 5 vertically to the array direction of transducer
units. Also, in between the adjacent transducer elements within
each transducer unit is featured with a trench 6 separating
transducer elements of a depth of approximately halfway of a
silicon substrate 16. Incidentally, a feature of the transducer
element is not limited to a square.
[0065] FIG. 5 shows a top view of a single body of the transducer
element 3 according to the present embodiment. The transducer
element 3 comprises trenches 7, trenches 6, interconnection
combining transducer electrodes 8, 9 and 10, a transducer cell's
upper electrode 11, a sacrifice layer material removal hole 13 and
a through-hole electrode 14 from a bottom electrode. The back
surface (in the direction vertical to the drawing) of the
transducer cell's upper electrode 11 is featured with a cavity
which is indicated as a cavity periphery part 12.
[0066] The transducer element 3 is constituted by a plurality of
transducer cells, of which the number thereof is equal to the
number of cavities. FIG. 5 shows a configuration of four transducer
cells. The numerical 15 shows a dicing line for separating the
units.
[0067] FIG. 6 is a diagram of cross-section Aa-Ab of FIG. 5.
Referring to the cross section, a constituent unit indicated by the
numerical 30 is called a transducer cell of the transducer element
3 as noted above. A film covering the upper part of the transducer
cell 30 is called a membrane which is a film constituted by the
upper electrode 11, upper layer 24 above membrane and under layer
22 beneath membrane in the configuration shown in FIG. 6. The
membrane is an vibrating film fixed by members supporting membrane
20 on both ends of each transducer cell. A bottom electrode 19 is
structured on the surface of a silicon substrate 16 (at the bottom
of a concave part) between the members supporting membrane 20 in a
manner to be opposite to the upper electrode 11, and the bottom
electrode 19 is covered over with a dielectric film 27 (e.g.,
SiO.sub.2, Si.sub.3N.sub.4, Ta.sub.2O.sub.5, BaTiO.sub.3,
SrTiO.sub.3, AlN and such).
[0068] The bottom electrode 19 is equipped with the through-hole
electrode 14 from bottom electrode for electrically connecting the
bottom electrode 19 to a electrode pad 26 as signal input-output
terminal which is equipped on the bottom face of the silicon
substrate 16. Specifically, the bottom electrode 19 is electrically
continuous with the electrode pad 26 as signal input-output
terminal by way of an interconnection 28 featured on the hole
surface of the through-hole electrode 14.
[0069] The bottom surface of the silicon substrate 16 is covered
with a silicon oxide film 17. The upper electrode 11 and
interconnection combining transducer electrodes 10 are constituted
by a metallic film of Au, Al, Pt, Ta, Mo, W or such. The upper
electrode 11 is electrically continuous with a metallic film
covering the side and bottom surfaces of the trenches 6 and 7.
[0070] A ground electrode pad 25 is one for making the bottom
surface of the silicon substrate 16 electrically continuous with an
electrode featured on the bottom surface of the trenches 6 and 7
for connecting the upper electrode 11 to the ground (GND).
[0071] The dielectric film 27 is for amplifying a capacitance
between the upper electrode 11 and bottom electrode 19 which
sandwich a cavity. A depletion layer 18 is one in a state of an
electron or electron hole hardly existing, and there is a case of
reducing a capacity possessed by a depletion layer, that is
reducing a parasitic capacitance by applying a reverse bias.
[0072] Note that a cavity (i.e., an air gap) 21 is a space
surrounded by the membrane, member supporting membrane 20, bottom
electrode 19 and dielectric film 27. Incidentally, a sacrifice
layer is formed in the cavity in terms of the production process
and a under layer beneath membrane 22 (Si.sub.3N.sub.4) is equipped
with a sacrifice layer removal hole 23 for removing the sacrifice
layer followed by removing the sacrifice layer from the hole when
forming the cavity 21.
[0073] A "contact resistance" between the ground electrode pad 25
and electrode featured on the bottom of the trenches 6 and 7 is
configured to be minimally small (i.e., an ohmic contact). The
numerical 29 shows a diffusion region.
[0074] Describing on an operation of the transducer cell 30, an
application of a voltage to a pair of electrodes of the upper
electrode 11 and bottom electrode 19 makes the electrodes mutually
pull each other, followed by reverting back to the original state
when reducing the voltage to zero. This movement causes the
membrane to vibrate, resulting in generating an ultrasound and
transmitting it to the upward direction of the upper electrode
11.
[0075] Next is a description of a production process of the c-MUT
according to the present embodiment by referring to FIG. 7 (i.e.,
FIGS. 7A, 7B and 7C).
[0076] First, the top surface of an N type silicon substrate 40 (of
a thickness of 100 through 500 micrometers) is masked by an oxide
film (SiO.sub.2) 41 (step 1). The mask forming forms an oxide film
of a thickness of 3000 to 4000 angstroms for example by a Wet
oxidization method. This is followed by a photolithography process
applying a patterning for featuring a through-hole 42 for
through-hole electrode from bottom electrode and by an etching
process removing the patterned oxide film.
[0077] Next is to apply an Inductively Coupled Plasma-Reactive Ion
Etching (ICP-RIE), thereby penetrating a through-hole 42 where it
is not masked in the step 1 (step 2).
[0078] Next is to form the depletion layer 43 (step 3). First is to
mask the bottom surface of the N type silicon substrate 40 with an
oxide film (SiO.sub.2), followed by applying a patterning to the
top and bottom surfaces of the N type silicon substrate 40 for
forming the depletion layer 43 in a photolithography process and
removing the oxide film patterned in the etching process. It is
then followed by doping a P type ion (Dope (P+)) and applying a
heat treatment, thereby forming a P type diffused layer.
[0079] The next is to form a contact layer (N+) 44 on both surfaces
(step 4). The mask forming process, photolithography process and
etching process mask other than a part for forming a contact layer
44 with SiO.sub.2. It is followed by doping an N type ion (Dope
(N+)) to the unmasked part, and applying a heat treatment, thereby
forming an N type diffusing layer. This is applied to the contact
layers (N+) 44 of both surfaces of the silicon substrate.
[0080] The next is to form an electrode film (Pt/Ti) 45 on both
surfaces (step 5). The first is to remove the mask 41, and mask a
part other than that part for forming an electrode film with a
resist material, followed by forming an electrode film 45 by means
of a sputtering and removing the resist material masked in the
liftoff process. Note that a material of the electrodes may be
Au/Cr, Mo, W, phosphor bronze, Al or such, in lieu of being limited
to Pt/Ti.
[0081] The next is to form a dielectric film (step 6). The
dielectric film (e.g., SrTiO.sub.3) 50 is formed by being subjected
to the mask forming process, sputtering process and liftoff
process. Note that the dielectric film 50 may use a material having
a high dielectric constant, such as barium titanate BaTiO.sub.3,
barium-strontium titanate, tantrum pentoxide, niobium
oxide-stabilized tantrum pentoxide, aluminum oxide or titanium
oxide TiO.sub.2, in lieu of the material being limited to
SrTiO.sub.3.
[0082] The next is to form a layer for supporting membrane (step
7). The application of a mask to apart other than ones for forming
the member supporting membrane is followed by a chemical vapor
deposition (CVD) forming an SiN layer and removing the mask, thus
resulting in forming the member supporting membrane formed by the
SiN.
[0083] The next fills in between the member supporting membrane
formed in the step 7 with a polysilicon 52 as the sacrifice layer
(step 8). Note that a material for the sacrifice layer may use a
material allowing an etching, such as SiO.sub.2 in lieu of being
limited to a material such as polysilicon which is used for the
present embodiment.
[0084] The next forms a under layer beneath membrane 22 (step 9).
The first step masks a part becoming a hole 54 for etching out of
sacrifice layer material and trench 55, followed by the CVD forming
an SiN film 53 and removing the mask. This results in forming the
membrane 53 formed by the SiN, the hole 54 and the trench 55.
[0085] The next removes the sacrifice layer 52 by means of an
etching (step 10). Since the present embodiment is configured to
use a polysilicon for the sacrifice layer, the etching is carried
out by using XeF.sub.2 as an etching agent for removing the
sacrifice layer (of polysilicon) from the hole 54 for etching out
of sacrifice layer material. This results in forming the cavity 56
and trench 55.
[0086] The next closes the hole 54 for etching out of sacrifice
layer material (step 11). First masks the bottom (i.e., a contact
electrode) of the trench 55 and forms an SiN film on the entirety
of the top surface of the element by means of the CVD. It is
followed by removing the mask to expose the bottom (i.e., the
contact electrode) of the trench 55.
[0087] The last step masks parts other than interconnection
combining transducer electrodes 8, 9 and 10, transducer cell's
upper electrode 11, bottom electrode of the trench 7, and bottom
electrode of the trench 6, and forms an electrode film (Pt/Ti) 61
on the entire top face of the transducer element by subjecting to
the sputtering and liftoff (step 12), thereby completing the
transducer element 3 as shown in FIG. 5.
[0088] Note that the forming of the electrode film (and the contact
layer), that is, the process for forming the electrode in the
trench (i.e., the process for making it conductive) is carried out
by means of an ion implantation or CVD and a diffusion process, or
a physical vapor deposition (PVD), according to the present
embodiment.
[0089] As described above, the forming of the ground electrode in
the trench eliminates a necessity of equipping a separate zone for
a ground electrode within the transducer element and prevents a
reduction of the area size ratio of an ultrasound output zone to
the transducer element. Also, the equipment of the trench enables a
suppression of an influence of a crosstalk between the adjacent
elements.
[0090] Note that the present embodiment exemplifies a radial type
c-MUT; the present invention, however, may also be applied to a
convex type, linear type or sector type c-MUT, in lieu of being
limited to the present embodiment.
First-2 Embodiment
[0091] Described for the present embodiment is a variation of a
form of the trench featured in a transducer element.
[0092] FIG. 8 exemplifies a variation of a trench form according to
the present embodiment (part 1). The numerical 70 and 71 indicate
trenches. The numerical 76 indicates a silicone substrate. The
numerical 72 (i.e., 72a, 72b and 72c) indicate contact electrodes
on the top face side of the silicone substrate 76. The numerical 73
(i.e., 73a, 73b and 73c) indicate contact layers featured in the
neighborhood of the contact electrodes 72 (i.e., 72a, 72b and 72c).
The numerical 74 indicates a contact electrode on the lower face
side of the silicon substrate 76. The numerical 75 indicates a
contact layer featured in the neighborhood of the contact electrode
74. The numerical 77 and 78 indicate SiN layers. The numerical 79
indicates an electrode film.
[0093] The numerical 70 indicates the case of widening the opening
part wider than the bottom by forming the trench in a taper form.
Such configuration enables a use of a sputtering for forming a film
on an electrode. Also enabled is a forming of a thicker film as a
result of an easy attachment of an electrode film by means of a
sputtering as compared to the case of the side face of a trench
being perpendicular. This improves a reliability of wiring.
[0094] The numerical 71 indicates the case of forming an irregular
surface on the surface of the trench side surface by means of Bosh
process. The Bosh process is one for repeating an etching and a
passivation (for providing a surface with protective film so as not
to occur a chemical reaction) processes alternately by using
C.sub.4F.sub.8 and SF.sub.6 as reaction gases. It enables a process
of a high aspect ratio. In the case of forming a trench by the Bosh
process, a change of timing between the passivation and etching
makes it possible to form a taper and an irregularity.
[0095] A common Bosh process is capable of forming a wavy
irregularity in the order of ones to tens nanometers. The present
embodiment, however, is configured to form an irregularity of the
order of a sub-micrometer on the side walls for raising the
strength of adhesion. This irregularity improves an adhesiveness of
the conductive film connected to the SiN, which is the same
material as an invested membrane, and the upper electrode. It also
improves an adhesiveness of a later described ultrasonic
attenuation material, leading to an improvement of strength when
dicing by a precision dicing.
[0096] As such, the forming of surface irregularity on the side
surface of the trench by using the Bosh process enlarges a surface
area size and makes an electrode film and SiN film which are
invested by the process thereafter hard to come off. Meanwhile, the
GND of the contact electrodes 72 (i.e., 72a, 72b and 72c) existing
on the bottom of the trench is connected to a contact electrode 74
by way of the silicon substrate 76.
[0097] The trench on the left side of FIG. 8 exemplifies the case
of the bottom being wider than the opening part. As such, the
feature of the trench may be discretionary.
[0098] FIG. 9 exemplifies a variation of a trench form according to
the present embodiment (part 2). FIG. 9 shows the case of cutting
the bottom of the trench deeper into the inside of a silicon
substrate 76 than the case of FIG. 8. This is produced by etching
down to the silicon substrate 76, followed by forming a contact
layer 73 and filming an electrode with the contact layer 73 as the
base. That is, the forming of the contact layer is followed by
forming an SiN film (i.e., closing the hole for removing a
sacrifice layer) by means of the CVD and filming a strong
corrosion-resistant electrode member as a base electrode before
filming an electrode 79 which is connected to a membrane so that
the contact layer surface does not have a resistance due to such as
natural oxidization.
[0099] As described above, the distance between the contact
electrodes 72 (i.e., 72a, 72b and 72c) and contact electrode 74
becomes shorter, reducing an electrical loss, thereby improving a
reliability of the wiring.
[0100] Since a dry etching is employed, it is possible to apply
etching in wavy line provided that there is no problem of a
mechanical strength. That is, a common trench forming (likewise a
shearing) is carried out by using a dicing saw, which is only
capable of forming a straight line trench. However, a dry etching
such as ICP-RIE is capable of forming a trench of discretionary
form, such as a wavy form.
[0101] Meanwhile, if a trench surface is an indeterminate form, a
determinate resonance is difficult to occur because lengths are
different and therefore it is beneficial in reducing a crosstalk.
Also beneficial is that it is easy to take out a ground electrode
to the back of the substrate.
[0102] The configuration of having a trench in the silicon
substrate provides a benefit of reducing a crosstalk. That is, an
ultrasound is transmitted and received by a flexion movement of the
membrane, and the flexion movement allows a generation of crosstalk
between the adjacent elements due to an vibration such as Lamb wave
and Stoneley wave. The flexion movement transmits a reactionary
longitudinal vibrating stress to the member supporting membrane.
This vibration reaches at a silicon substrate surface from base
parts of the member supporting membrane, propagates along the
surface of the silicon substrate, and propagates reversely along
the same path to the next neighbor element, thus causing a
crosstalk. It is possible to reduce an occurrence of such a
crosstalk.
[0103] FIG. 10 exemplifies a variation of a trench form according
to the present embodiment (part 3). FIG. 10 shows the case of
joining contact layers on both faces of a silicon substrate 76. In
the case of the silicon substrate being thin as shown in FIG. 10,
or of etching a (GND-use) trench on the silicon substrate, followed
by forming contact layers 73 and 75, diffusing them, and forming
the contact layers, then the thin contact layers can be mutually
connected. This configuration forms a low resistance zone between a
contact electrode 72 and contact electrode 74, making an easy
electrical conduction and reducing an electrical loss, thereby
improving a reliability of a wiring.
First-3 Embodiment
[0104] Described for the present embodiment is a variation of a
c-MUT element.
[0105] FIG. 11 is a diagram exemplifying a variation of a c-MUT
element according to the present embodiment (part 1).
[0106] The numerical 80 indicates a trench. The 86 indicates a
silicon substrate. The 82 indicates a contact electrode on the
upper face side of the silicon substrate 86. The 83 indicates a
contact layer formed in the neighborhood of the contact electrode
82. The 84 indicates a contact electrode on the bottom face side of
the silicon substrate. The 85 indicates a contact layer formed in
the neighborhood of the contact electrode 84. The 87 and 88
indicate SiN layers, respectively. The 89 indicates an electrode
film. The 90 indicates an SiO.sub.2 film. The 81 indicates a
through-hole electrode from bottom electrode.
[0107] FIG. 11 shows the case of the etching also applied to the
surrounding area of the contact electrode on the bottom face of the
silicon substrate 86. This configuration is for masking also the
bottom surface of the silicon substrate with SiO.sub.2 at the stage
of the step 1 shown in FIG. 7 and applying the etching to the
electrode contact part by means of a wet etching so as to make it
concave form. This configuration further shortens the distance
between the contact electrodes (82 and 84) on both faces and
accordingly reduces an electrical loss and therefore the
reliability of wiring is improved.
[0108] Also, the adoption of the configuration of the trench
invading the silicon substrate 86 provides a benefit of reducing a
crosstalk as in the case of FIG. 9. That is, while it transmits and
receives an ultrasound by the flexion movement of the membrane, the
flexion movement generates a crosstalk between the adjacent
elements due to a Lamb wave or Stoneley wave. The flexion movement
transmits a reactionary longitudinal vibrating stress to the member
supporting membrane. This vibration reaches at a silicon substrate
surface from base parts of the member supporting membrane,
propagates along the surface of the silicon substrate, and
propagates reversely along the same path to the next neighbor
element, thus causing a crosstalk. It is possible to reduce an
occurrence of such a crosstalk by adopting the configuration of the
trench invading the silicon substrate 86. It also provides the
benefit of easing an extraction of the ground electrode to the back
of the substrate.
[0109] Note that a Wet oxidization film of SiO.sub.2 may be
utilized instead of forming the depletion layer. The reason is that
the Wet oxidization film can obtain more exact film. Also, it may
be possible to apply an N+ doping in the trench if it is an N type
silicon substrate after forming the trench and apply a diffusion
process by heating, thereby forming a contact layer (N+).
Meanwhile, the trench may be such that a part of the bottom is
deeper, or that a hole reaches at the bottom face of the silicon
substrate.
[0110] FIG. 12 exemplifies a variation of a c-MUT element according
to the present embodiment (part 2). FIG. 2 shows the case of
forming a cavity 91 by applying an etching to a silicon substrate
86. In this case, the silicon substrate 86 also functions as member
supporting membrane.
[0111] First process applies an anisotropic etching to Si by using
Tetramethyl Ammonium Hydroxide (TMAH). This process forms a cavity
91 and a trench 80 of a prescribed depth on the upper face side of
the silicon substrate 86 and a concave part 95 on the bottom face
side thereof.
[0112] The next forms a through hole 81 by means of the ICP-RIE. It
is followed by filming applying a Wet oxidization for forming an
oxide film 90 (used as a substitute for a depletion layer). Then
forms a film of the bottom electrode 92 (Pt/Ti) to invest the side
wall of the through hole 81 with a conductor.
[0113] The next forms a film of a dielectrics 93 on the top surface
of the bottom electrode 92, followed by applying a heat treatment.
Then forms a sacrifice layer in the cavity 91 and films an SiN
membrane 87 over the sacrifice layer. Then putting a hole 94 in the
filmed membrane and remove the sacrifice layer by applying an
etching. It is followed by closing the hole used for a removal of
the sacrifice layer by SiN. It is then covered over with an upper
electrode 89.
[0114] This process eliminates a necessity of adding a specific
process for forming the member supporting membrane, thereby
enabling a reduction of the number of processes.
[0115] FIG. 13 exemplifies a variation of a c-MUT element according
to the present embodiment (part 3). FIG. 14 exemplifies a variation
of a c-MUT element according to the present embodiment (part 4).
FIGS. 13 and 14 show the case of filling a trench 80 with a resin
100.
[0116] The difference between FIGS. 13 and 14 is either a contact
electrode on the bottom face of a silicon substrate 86 is formed in
a concave or not. If the trench 80 is not filled with the resin
100, a transverse standing wave (i.e., an extraneous vibration) may
be excited within a transducer, thus unable to obtain a good
ultrasonic characteristic. Therefore, the trench 80 is filled with
the resin 100. Its material uses, as an ultrasonic attenuation
material, a flexible composite resins mixing such material as a
silicone resin, epoxy resin and urethane resin with powder of such
material as tungsten fine powder and glass bubble in order to
attenuate an vibration caused by an extraneous ultrasound. This
configuration makes it possible to suppress an extraneous
vibration.
[0117] Incidentally, among the trenches shown in FIGS. 3 through 6
(i.e., the trenches are featured vertically and horizontally when
viewing the transducer elements from above), the types of
transducers having a curved array of the transducers as in the case
of the convex and radial types are applied by a dicing on at least
one side (e.g., the top face side). If a filled resin exists in
such an event, a stress is reduced so as to decrease a peeling,
chipping or such of an electrode. Such decrease of a chipping as
well as an improvement of a reliability of a wiring can shorten the
distance between the cavity and trench, resulting in increasing a
working part from a design view point, thereby leading to an
increased sound pressure per unit area size, that is, an improved
sensitivity and a miniaturization of size.
[0118] FIG. 15 exemplifies a variation of a c-MUT element according
to the present embodiment (part 5). FIG. 15 is a diagram showing
the case of joining a transducer element to a flexible printed
circuit (FPC) by using a conductive resin 101. Note that an
anisotropic conductive film (ACF) or a ball bump made of such
material as Au and solder in place of the conductive resin 101.
Also, an air gap 104 between the FPC and the lower face of the
silicon substrate 86 may be filled with a resin.
[0119] Also, the trench 80 may be featured with a dicing trench 105
by dicing in place of filling with a resin, or the trench 80 may be
filled with a resin followed by featuring a dicing trench 105 by
dicing. Or, it may be such that a forming of a transducer by
curving after a dicing, followed by filling with a resin material
having a large attenuation. As for a depth of the dicing trench,
the dicing must be as deep as reaching the conductive resin 101 if
it is a type curving the transducer elements such as a convex type
and radial type; while a type not curving the elements, such as a
linear type, however, al least the silicone substrate needs to be
diced. Meanwhile, if an electrode 103 of a silicon on the FPC side
is formed as concave or hole, a positioning function is obtained
and also a mechanical strength of the connection due to an
expansion of an adhering area size, thereby enabling a production
of a highly reliable transducer.
[0120] Also, a laser beam may be used for penetrating a silicon
substrate. The use of the laser beam enables a trench cutting or
shearing of a discretionary form, likewise a dry etching. This
obtains a benefit of reducing a crosstalk, and making a wavy line
increases a contact area size increases, increasing adhesion
strength. Also, an ability of making a form of elements
discretionary enables a discretionary cell layout, thereby making
it possible to achieve a high density configuration (e.g., an area
size ratio of cells to that of an element is large), which is very
important for accomplishing a high sensitivity within a limited
space such as endoscope.
[0121] Incidentally, a trench is commonly straight as shown in FIG.
5 when viewing a transducer element from above, it is, however,
possible to form a curved trench if a photolithography and an
etching are applied. FIGS. 16A, 16B and 16C exemplify it.
[0122] FIG. 16 (i.e., FIGS. 16A, 16B and 16C) is a diagram
exemplifying the case of forming a trench of a curved line when
viewing the transducer element 3 according to the present
embodiment from above. FIG. 16A exemplifies the case of making
trenches 111 (i.e., a horizontal trench 111a and a vertical trench
111b) surrounding a transducer element 3 curved lines and dicing in
straight lines (i.e., dicing lines 110). As such, all around the
transducer element may have a wavy line trench.
[0123] FIG. 16B exemplifies the case of making trenches 111a and
111b surrounding a transducer element curved line and dicing in
curved lines (i.e., dicing lines 110). It is possible to apply a
dicing along the curved trench by employing a laser dicing.
[0124] FIG. 16C exemplifies the case of making a vertical direction
trench 111b a straight line and a horizontal direction trench a
curved line, among the trenches surrounding a transducer element,
and dicing in straight lines (i.e., dicing lines 110). The
numerical 112 is a ground electrode. As such, it may have a partly
wavy line trench structure.
[0125] In addition to the examples shown in FIG. 16, a trench form
and a dicing form may apparently be a rectangular wave form,
saw-tooth wave form, or indeterminate form.
[0126] A resonance is stronger and accordingly a standing wave
tends to occur in the case of a straight line trench, while
extraneous vibrations are weaker as a result of canceling each
other in the case of a non-straight line trench. This accordingly
reduces a crosstalk, improves an S/N ratio and provides a high
image quality image. Note that an adoption of the same dicing
position and ultrasonic attenuation resin as that of a straight
line configuration makes it possible to obtain the same function
and effect.
[0127] As described above, the first embodiment is configured to
eliminate a necessity of decreasing an area size ratio of a cell
zone to the entirety of a c-MUT featured with trenches respectively
on both ends of a transducer element, thereby negating a
possibility of reducing an output of a generated ultrasound.
Second Embodiment
[0128] A description for the present embodiment is on an endo
cavity ultrasonic diagnosis system enabling a noncontact diagnosis
by using a radial scanning type c-MUT, in addition to being capable
of obtaining a tomographic image by being stationary in contact
with an endo cavity wall similar to a conventional technique.
[0129] FIG. 17 shows an outline of an endo cavity ultrasonic
diagnosis system according to the present embodiment. Referring to
FIG. 17, the endo cavity ultrasonic diagnosis system 201 primarily
comprises an ultrasonic endoscopic scope unit 202, a signal process
unit 203, an image process unit 205 and a display unit 204. Note
that FIG. 17 indicates only a reception signal series, while
omitting a transmission signal series from the drawing.
[0130] The ultrasonic endoscopic scope unit 202 is equipped with a
c-MUT 202-1 on the head part thereof. The primary functions of the
c-MUT 202-1 is for first inserting the head part of the ultrasonic
endoscopic scope unit 202 into an endo cavity, transmitting an
ultrasound from the c-MUT 202-1, receiving an ultrasound reflected
within the endo cavity thereby and converting the received
ultrasound into an electric signal.
[0131] The signal process unit 203 analyzes the electric signal
obtained by the ultrasonic endoscopic scope unit 202 and performs
an arithmetic operation of it. The signal process unit 203
comprises a storage control unit 203-1, a storage unit 203-2, an
arithmetic operation unit 203-3 and a transducer state discernment
unit 203-5.
[0132] The transducer state discernment unit 203-5 is configured
for discerning a state of the c-MUT, for example, whether the c-MUT
202-1 is on the outside of a human body or in the inside thereof
and not in contact with an endo cavity wall, or in contact
therewith. The transducer state discernment unit 203-5 is
constituted by a state detection unit 203-5a and a detection
information discernment unit 203-5b. The state detection unit
203-5a is for detecting a state of the c-MUT 202-1. The detection
information discernment unit 203-5b is for discerning a state of
the c-MUT 202-1 based on information detected by the state
detection unit 203-5a. Note that the transducer state discernment
unit 203-5 may be included in the ultrasonic endoscopic scope unit
202, in the signal process unit 203, or in both of them in
accordance with the discernment method.
[0133] The storage unit 203-2 is for storing sense information
(e.g., received reflection wave and standing wave) sensed by the
c-MUT 202-1. A plurality of storage units 203-2 exists. Note that a
plurality of physical storage units or logical zones may exist
(i.e., securing a plurality of logical storage zones within a
single storage apparatus, with each storage zone being handled as a
storage unit).
[0134] The storage control unit 203-1 is for storing sense
information sensed by the c-MUT 202-1 in a storage unit 203-2
corresponding to a discernment result based on the discernment
result of the transducer state discernment unit 203-5.
[0135] The arithmetic operation unit 203-3 is for performing an
arithmetic operation (e.g., a difference and a correlation
function) based on the sense information stored in each storage
control unit 203-2. A plurality of combinations of arithmetic
operations exists, enabling the operation in accordance with each
purpose.
[0136] The image process unit 205 is constituted by an image
buildup unit 205-1. The image buildup unit 205-1 is for building up
an ultrasonic diagnosis image (e.g., a contour image of an endo
cavity wall, an endo cavity organization section image, or an image
that combines the aforementioned) from the operated signal based on
the result of the arithmetic operation at the arithmetic operation
unit 203-3.
[0137] The display unit 204 is for displaying an ultrasonic
diagnosis image generated at the image process unit 205, including
a monitor (i.e., a display) 204-1 for example. Note that the
display unit 204 may be output equipment such as a printer, in lieu
of being limited to a display.
[0138] FIG. 18 shows an external configuration of the ultrasonic
endoscopic scope 202 according to the present embodiment. The
ultrasonic endoscopic scope 202 comprises a control section 209 on
the base end of a slender insertion tube 212, and a scope connector
211 on one end. From a side part of the control section 209 extends
a universal cord 210 to be connected to a light source apparatus
(not shown herein). The scope connector 211 is further connected to
the signal process unit 203.
[0139] The insertion tube 212 is constituted by serially
connecting, from the head side, a capacitive radial sector scanning
array ultrasonic transducer 206 equipped on the head part, a freely
bending section 207, and a flexible tube section 208 having
flexibility. The control section 209 is equipped with a bending
control knob 209a, enabling a curving of the bending section 207 by
operating the bending section knob 209a. The head part is also
equipped with an illumination lens cover, constituting an
illumination optical part for transmitting an illumination light
onto an observation region, an observation-use lens cover
constituting an observation optical part for capturing an optical
image of an observation region, a forceps exit that is an opening
for projecting a treatment instrument, and such, which are not
shown herein.
[0140] FIG. 19 is a diagram showing a comprisal of a capacitive
radial sector scanning array ultrasonic transducer 206 (named as
"ultrasonic transducer", or "transducer" hereinafter) equipped on
the head part of the ultrasonic endoscopic scope unit 202 shown in
FIG. 18. The ultrasonic transducer 206 is constituted by a
two-dimension array transducer 220, a transmission/reception
circuit 221 and a coaxial cable bundle 222. The two-dimension array
transducer 220 is formed by arraying a plurality of transducer
elements. The coaxial cable bundle 222, being housed in the
insertion tube 212, is made by bundling a plurality of cables
connected to the individual transducer elements. The
transmission/reception circuit 221 is for controlling signals
exchanged with the transducer elements. That is, the
transmission/reception circuit 221 is capable of controlling a
scanning of a compound ultrasonic beam transmitted from the
ultrasonic transducer 206, and capable of performing not only a
radial scan 225 but also a sector scan 224 (i.e., an ultrasound
sector scanning plane) within a single element (in the cylindrical
longitudinal direction). This configuration enables a buildup of a
three-dimensional ultrasonic image. The two-dimensional array
transducer has been described in detail for FIGS. 3 through 6 of
the first embodiment, and therefore it is omitted here.
[0141] The next description is on a series of flow of operation of
the endo cavity ultrasonic diagnosis system 201 according to the
present embodiment.
[0142] FIG. 20 shows an ultrasonic anechoic cell 270 according to
the present embodiment. A cavity is featured in the inside of the
ultrasonic anechoic cell 270, and the ultrasonic transducer 206 is
inserted from the opening thereof as shown in FIG. 20, followed by
transmitting an ultrasound. In this event, the ultrasound is not
reflected because the ultrasonic anechoic cell 270 is structured by
a member absorbing the ultrasound (e.g., a urethane fiber, a foamed
silicone resin or the like). Therefore, transmitting an ultrasound
by an ultrasonic transducer within the ultrasonic anechoic cell
270, a reflectance wave is not received. Therefore, a charge of the
upper electrode does not change at the time of reception because
the membrane basically does not vibrate. In the case of an
extraneous vibration such as a standing wave occurring, however,
the charge on the membrane is changed by the influence, thus
requiring a detection of a change in the charge in this case. That
is, an extraneous vibration which is not converted into a
transmission ultrasound remains as a standing wave associated with
an vibration of the membrane at the time of transmission, and the
vibration is overlapped as a noise signal at the time of an actual
echo reception, ushering in decreasing an S/N ratio.
[0143] FIG. 21 (FIGS. 21A and 21B) show a state of inserting the
ultrasonic transducer 206 into an endo cavity, with FIG. 21A
showing a state of inserting it into a mouth and FIG. 21B showing a
state of transmitting and receiving an ultrasound by having the
ultrasonic transducer 206 contact with a stomach wall.
[0144] The transmission and reception of an ultrasound is performed
in three states, i.e., the case of performing it in an ultrasonic
anechoic cell 270 (refer to FIG. 20) (named as "state 1"
hereinafter), the case of performing it in the air (not in contact
with an endo cavity wall) between the insertion into an endo cavity
and arrival at an observation region (refer to FIG. 21A) (named as
"state 2" hereinafter) and the case of performing it with the
ultrasonic transducer in contact with an endo cavity wall (refer to
FIG. 21B) (named as "state 3" hereinafter).
[0145] In the case of using a conventional piezoelectric element,
it has been only possible to obtain an ultrasonic image in the
state of the element in contact with an observation region, whereas
a c-MUT, having an acoustic impedance of the ultrasonic
transmission/reception face larger than the air and smaller than a
live tissue, thus making it possible to obtain an ultrasonic image
in the air (i.e., a state of not in contact with an endo cavity
wall). This makes it possible to easily obtain a reflectance wave
from an endo cavity wall, enabling a measurement of a contour of a
luminal wall, that is, a surface irregularity, while inserting the
ultrasonic transducer. The c-MUT is capable of transmitting and
receiving a high frequency ultrasound of ones MHz, thus enabling a
high accuracy detection of a surface irregularity.
[0146] FIG. 22 shows an outline of an internal comprisal of an endo
cavity ultrasonic diagnosis system according to the present
embodiment. The endo cavity ultrasonic diagnosis system is
constituted by an ultrasonic endoscopic scope unit 202 and an
ultrasonic endoscope diagnostic apparatus 300.
[0147] The ultrasonic endoscopic scope unit 202 comprises a c-MUT
301, an optical sensor 302, a charge amplifier 303 and a pulser
(i.e., a pulse generation circuit) 304.
[0148] The ultrasonic endoscope diagnostic apparatus 300 comprises
an signal process circuit for optical sensor 305, a switch circuit
306 (including a selection SW1 for terminals (307), a selection
terminal SW2 (308), and a selection terminal SW3 (309)), AD
converters 310, 311 and 312, storage apparatuses 313, 314 and 315,
arithmetic operation circuits 316, 317 and 318, a switch circuit
319 (including a selection terminal Q1 (320), a selection terminal
Q2 (321) and a selection terminal (322)), an operation unit 323, an
image converter (i.e., a digital scan converter) 324, and a monitor
204-1.
[0149] The pulser 304 is a circuit for generating an electric
signal for driving the c-MUT 301.
[0150] The charge amplifier 303 comprises the function of
performing an impedance conversion (i.e., converting from a high
impedance to a low impedance), that of detecting a charge on an
electrode surface of the c-MUT 301 and that as amplifier. The
function of detecting a charge is to detect a charge as a result of
the c-MUT 301 receiving a reflectance wave, causing the membrane to
vibrate in accordance with the reception intensity of the
reflectance wave and causing a variation of the charge on the upper
electrode in response to the vibration. Note that the present
embodiment is configured by assuming the case of detecting not only
the charge caused by receiving a reflectance wave but also a charge
caused by an extraneous vibration such as a standing wave. These
are included in a term "reception signal" in the following
description.
[0151] The optical sensor 302 is for detecting a brightness of the
surrounding area of the c-MUT 301.
[0152] The signal process circuit for optical sensor 305 is for
discerning a brightness/darkness based on a signal output from the
optical sensor 302. That is, it is capable of analyzing a signal
based on the light volume detected by the optical sensor and
discerning a difference of brightness in the surrounding of the
c-MUT 301.
[0153] An example configuration is so as to detect the highest
brightness among the above described three states in the case of
transmitting and receiving before inserting the ultrasonic
transducer 301 into an endo cavity, that is, in the ultrasonic
anechoic cell 270 (i.e., the state 1). Then, a brightness is
decreased when inserting the ultrasonic transducer 301 into an endo
cavity until reaching at an observation region (i.e., the state 2),
and therefore the configuration is for detecting the reduced
brightness. Then, when the ultrasonic transducer reaches at an
observation region (i.e., the state 3), it is configured to detect
reflectance light as a result of the light emitted from the light
guide (not shown herein) equipped in the surrounding of the
ultrasonic transducer being reflected by the endo cavity wall, and
therefore it is capable of detecting a higher brightness than the
state 2.
[0154] Therefore, the setup of discernment information for the
signal process circuit for optical sensor 305 is such that the
ultrasonic transducer 301 is judged to be prior to an insertion
into an endo cavity (i.e., the state 1) at an initial state. Then,
the brightness decreases from the insertion into an endo cavity
until reaching at an observation region (i.e., the state 2), and
therefore the judgment is a state of the state 2 if a signal from
the optical sensor indicates a value equal to or lower than a
threshold value. Then, if the brightness increases and if a signal
from the optical sensor indicates a value equal to or higher than
the threshold value, the ultrasonic transducer is judged to be in
contact with an observation region (i.e., the state 3).
[0155] The switch circuit 306 is for turning on and off the
selection terminals SW1, SW2 and SW3 in response to an output of
the signal process circuit for optical sensor 305. If the signal
process circuit for optical sensor 305 judges that the ultrasonic
transducer is in a state of being prior to an insertion into an
endo cavity (i.e., the state 1), it outputs a signal effecting the
state so that the selection SW1 for terminals (307) is turned On as
a result of receiving the signal at the switch circuit 306. If the
signal process circuit for optical sensor 305 judges that the
ultrasonic transducer is in a state of being inserted into an endo
cavity and on the move to an observation region (i.e., the state
2), it outputs a signal effecting the state so that the selection
terminal SW2 (308) is turned On as a result of receiving the signal
at the switch circuit 306. And, if the signal process circuit for
optical sensor 305 judges that the ultrasonic transducer is in a
state of reaching at an observation region (i.e., the state 3), it
outputs a signal effecting the state so that the selection terminal
SW3 (309) is turned On as a result of receiving the signal at the
switch circuit 306.
[0156] A reception signal based on charge information detected at
the charge amplifier 303 is input to either of the AD converter
310, 311 or 312 based on the destination of a changeover of the
switch circuit 306. The AD converter 310, 311 or 312 converts the
input analog signal into a digital signal. The converted signal is
input to either of the storage apparatus 313, 314 or 315, to be
stored therein, corresponding to the AD converter 310, 311 or
312.
[0157] The arithmetic operation circuits 316, 317 and 318 calculate
a correlation function among the reception signals (i.e.,
respective signals stored in the storage apparatuses 313, 314 and
315) obtained in the individual states, thereby making it possible
to remove, from the respective reception signals of the states 2
and 3, an extraneous vibrational wave component such as a standing
wave that is a noise component obtained in the state 1.
[0158] The correlation function includes a cross-correlation
function and an autocorrelation function. Explaining the case of
using a cross-correlation function,it is the function of a shift
amount of .tau. when a waveform of one of two signals is delayed
for the .tau. and is defined as the following expression: R xy
.function. ( t ) = lim T .fwdarw. 0 .times. 1 T .times. .intg. - T
/ 2 T / 2 .times. x .function. ( t ) .times. y .function. ( t +
.tau. ) .times. .times. d t ; ( 1 ) ##EQU1##
[0159] where x(t) is a waveform based on a reception signal in the
state of "m" (where an m is discretionary), and y(t) is a waveform
based on a reception signal in the state of "n" (where an n is
discretionary).
[0160] The use of the cross-correlation function R.sub.xy enables a
calculation of similarity between two signals. If the two signals
are completely different from each other, the cross-correlation
function R.sub.xy is close to zero regardless of a .tau.. This
accordingly makes it possible to detect a component of an
extraneous vibration such as a standing wave and accordingly remove
the component. Note that a cross-correlation function R.sub.xy can
be obtained by applying an inverse Fourier transform to a
cross-spectrum.
[0161] Meanwhile, an autocorrelation function can also be used. The
autocorrelation function is a function of a shift amount of .tau.
using a waveform x(t) and a waveform x(t+.tau.) that is displaced
by .tau. and it is defined by the following expression: R xx
.function. ( t ) = lim T .fwdarw. 0 .times. 1 T .times. .intg. - T
/ 2 T / 2 .times. x .function. ( t ) .times. x .function. ( t +
.tau. ) .times. .times. d t ( 2 ) ##EQU2##
[0162] The autocorrelation function R.sub.xx becomes a maximum with
.tau.=0, that is, when it is substituted by a product of itself so
that, if a waveform is cyclic, the autocorrelation function
indicates peaks in the same cycle as the waveform. If it is an
irregular signal and a variation occurs slowly, the autocorrelation
function indicates a high value where a .tau. is large, or if the
variation occurs quickly, then the autocorrelation function
indicates a high value where a .tau. is small, thus making the
.tau. a temporal indication of a variation. This makes it possible
to detect a component of an extraneous vibration such as a standing
wave, and accordingly remove the component. Note that an
autocorrelation function can be obtained by applying an inverse
Fourier transform to a power spectrum.
[0163] Note also that another configuration may be so as to remove
an extraneous component such as a standing wave by calculating a
difference between a waveform based on a reception signal in a
state of "m" and that based of a reception signal in a state of
"n", other than the method of using a correlation function.
[0164] Input to the arithmetic operation circuit 316 are a signal
stored in the storage apparatus 313 (i.e., the reception signal in
the state 1) and a signal stored in the storage apparatus 314
(i.e., the reception signal in the state 2). The arithmetic
operation circuit 316 calculates a correlation of the two signals
or a difference between the two, thereby removing a component of an
extraneous vibration from the reception signal in the state 2.
[0165] Input to the arithmetic operation circuit 317 are a signal
stored in the storage apparatus 314 (i.e., the reception signal in
the state 2) and a signal stored in the storage apparatus 315
(i.e., the reception signal in the state 3). The arithmetic
operation circuit 317 likewise calculates a correlation of the two
signals or a difference between the two, thereby removing the
reception signal in the state 2 from that in the state 3. This
configuration makes it possible to remove also an extraneous
vibration component simultaneously.
[0166] The arithmetic operation circuit 318 calculates a sum of the
signals obtained by the arithmetic operation circuits 316 and 317.
This obtains a contour image (i.e., surface irregularity
information of a luminal wall) and a cross-section image (i.e.,
information of a depth direction) thereof simultaneously. Note that
a correlation of signals obtained at the arithmetic operation
circuits 316 and 317 maybe calculated by using a correlation
function.
[0167] The operation unit 323 is for performing a changeover
operation of the switch circuit 319. An operation of the operation
unit 323 changes over the switches included in the switch circuit
319, thereby enabling a selection of an image in a state of a
desired output. That is, a signal subjected to an arithmetic
operation at the arithmetic operation circuit 316 can be output to
the image converter 324 if the selection terminal Q1 (320) is
selected. A signal subjected to an arithmetic operation at the
arithmetic operation circuit 318 can be output to the image
converter 324 if the selection terminal Q2 (321) is selected. And a
signal subjected to an arithmetic operation at the arithmetic
operation circuit 317 can be output to the image converter 324 if
the selection terminal Q3 (322) is selected.
[0168] A signal prior to being input to the image converter 324 is
a time axis signal; it is, however, converted into an image signal
by way of the image converter 324. And thus obtained image signal
is output to the monitor 204-1 and an ultrasonic diagnosis image is
displayed therein.
[0169] As described above, the use of the c-MUT makes it possible
to transmit and receive an ultrasound both in the states of the
ultrasonic transducer in contact with, and not in contact with, an
endo cavity wall, and transmit reception signals of the ultrasound
received in the respective states to the respectively corresponding
channels.
[0170] A "noncontact diagnosis" is enabled in addition to the
capability of obtaining a cross-sectional image by fixing the
ultrasonic transducer in contact with an endo cavity wall. The
"noncontact diagnosis" makes it possible to obtain organization
feature information of a luminal wall in the process of inserting
the ultrasonic transducer into the endo cavity. That is, an
ultrasonic diagnosis which used to be impossible to perform by the
conventional ultrasonic diagnosis.
[0171] Also, performing a signal process for calculating a
correlation or difference between reception signals obtained by the
respective states makes it possible to remove a standing wave
component (i.e., a noise component) that is an extraneous
vibration, thereby enabling an obtainment of a clearer ultrasonic
diagnosis image than before.
[0172] Also, an extraneous vibration component such as a standing
wave that is a noise component can be removed from an ultrasonic
diagnosis image, thereby enabling an obtainment of a clearer image
signal. By this, it is possible to obtain an ultrasonic diagnosis
image that expresses a clear contour feature of an endo cavity wall
even if the ultrasonic diagnosis image is photographed in a state
of the ultrasonic transducer not in contact with the endo cavity
wall.
[0173] Also, performing a signal process by combining reception
signals obtained in respective states is capable of obtaining a
contour image, and an endo cavity cross-section image, of an endo
cavity wall.
[0174] Also, a use of detection means such as an optical sensor
enables a detection of whether or not the ultrasonic transducer
contacts with an endo cavity wall and therefore a state of the
ultrasonic transducer can be detected.
[0175] Note that the present embodiment is configured to use a
radial type c-MUT for obtaining a contour image, and a live
organization cross-section image, of an endo cavity wall; an
extraneous vibration component such as a standing wave, however,
can be removed by adopting a convex type or linear type. Also, the
present embodiment is configured to use an optical sensor for
detecting a state of the ultrasonic transducer; the detection of
whether or not the ultrasonic transducer contacting with an endo
cavity wall, however, is possible by using a pressure sensor, for
example. And, the present embodiment is configured to transmit an
ultra sound within an ultrasonic anechoic cell for sensing only an
extraneous vibration component such as a standing wave; it may be,
however, an anechoic environment in which the ultrasound is not
reflected.
Third Embodiment
[0176] While the second embodiment is configured to detect whether
or not the ultrasonic transducer contacts with an endo cavity wall
by using an optical sensor, the present third embodiment describes
the case of detecting whether or not an ultrasonic transducer
contacts with an endo cavity wall by a difference of a received
ultrasonic frequency.
[0177] FIG. 23 is a graph showing a frequency characteristic when a
target object is contacting or not contacting with an ultrasonic
transducer according to the present embodiment. The vertical axis
of the graph shows a relative amplitude (i.e., values divided by a
maximum value of them in the vertical axis (i.e., normalized),
while the horizontal axis shows frequencies.
[0178] The numerical 330 shows a frequency characteristic in a
state of the ultrasonic transducer not in contact with an object.
The 331 shows a peak frequency (fc_non) in a state of the
ultrasonic transducer not in contact with an object (i.e., the
curve 330). The 332 is a frequency characteristic in a state of the
ultrasonic transducer in contact with an object. The 333 shows a
peak frequency (fc_con) in a state of the ultrasonic transducer in
contact with an object (i.e., the curve 332).
[0179] There is a large difference in the frequency characteristic
of the ultrasound transmitted between the ultrasonic transducer
being in contact and not in contact with an object, that is, an
organ wall of the endo cavity according to the graph. The FIG. 20
of the non-patent document 2, for example, notes such a change of
the frequency characteristic between the contact and noncontact.
The non-patent document 2 notes that a change in a frequency
characteristic between the contact and noncontact is caused by: (1)
difference in an acoustic impedance of an acoustic load (i.e.,
water and air) from the view point of a membrane, (2) an internal
pressure of a cavity located behind the membrane is different due
to an acoustic load (i.e., water and air), and (3) a transmission
of a high frequency ultrasound into the air is difficult.
[0180] Therefore, a provision of a threshold value between the
fc_con and fc_non enables a discernment of which state (i.e., the
curve 330 or curve 332) the ultrasonic transducer is in by using
the threshold value as a border.
[0181] FIG. 24 shows an outline of an internal comprisal of an endo
cavity ultrasonic diagnosis system according to the present
embodiment. FIG. 24 shows a configuration of removing the optical
sensor 302 and signal process circuit for optical sensor 305 and
adding a low pass filter 325 and a wave detector 326 from FIG.
22.
[0182] A signal based on charge information detected by the charge
amplifier 303 is input to the low pass filter 325 which is for
passing a signal of lower frequencies than a preset threshold.
Therefore, it is possible to discern that a signal passing the low
pass filter is a reception signal in the state of the ultrasonic
transducer not contacting with an object, while a signal unable to
pass it is a reception signal in the state of the ultrasonic
transducer contacting with the object.
[0183] The wave detector 326 is for detecting a wave of a signal
(i.e., an alternate current signal) output from the low pass filter
325 and converting it into a direct current (DC) signal for driving
the switch circuit 306. In the case of an ultrasonic reception
signal being a low frequency, it passes the low pass filter 325 and
the ultrasonic reception signal is input to the wave detector 326
and subjected to an AC/DC conversion. In the case of the ultrasonic
reception signal being a high frequency, it is cut by the low pass
filter 325 and therefore the ultrasonic reception signal is not
input to the wave detector 326, hence no output therefrom.
Meanwhile, a reception signal within the ultrasonic anechoic
chamber 270 is not observed other than a low level noise, and
therefore no output comes out of the wave detector 326. Therefore,
an output from the wave detector 326 is zero at the time of
detecting a calibration signal (refer to FIG. 20), is a high level
output at the time of inserting into a lumen (refer to FIG. 21A),
and is a low level output at the time of being fixed in contact
(refer to FIG. 21B). The switches of the switch circuit 306 is
changed over from the SW1 (307) to SW2 (308) to SW3 (309) in
accordance with the difference of the wave detection output, and a
reception signal in each of the state is transmitted to the AD
converters 310, 311 and 312. The operations thereafter are the same
as those of the second embodiment.
[0184] By the above operations, the discernment of the difference
in frequency characteristic makes it possible to detect whether the
ultrasonic transducer is on the outside of a human body, or in the
inside of an endo cavity and not in contact with an inner wall, or
in contact therewith, thereby enabling a detection of the state of
the ultrasonic transducer.
Fourth Embodiment
[0185] The present fourth embodiment describes a variation of a
signal process based on an ultrasonic reception signal obtained in
each state.
[0186] FIG. 25 shows an arithmetic operation control circuit 350
for performing a signal process of a plurality of patterns
according to the present embodiment. The arithmetic operation
control circuit 350 is a group of circuits corresponding to the
arithmetic operation process circuits (316, 317 and 318) and switch
circuit 319 which are shown in FIG. 22.
[0187] The arithmetic operation control circuit 350 comprises
distributors 351, 352 and 353, arithmetic operation process
circuits 354, 355, 356, 357, 358 and 359, and a switch circuit 361.
The distributors 351, 352 and 353 are for distributing signals
output from the respective storage apparatuses 313, 314 and 315 to
the respective arithmetic operation process circuits. The
arithmetic operation process circuits 353 through 359 are for
calculating a correlation, difference or sum of the input two
reception signals.
[0188] The second or third embodiments is configured in a manner
that a switch control signal 341 output from the signal process
circuit for optical sensor 305 (refer to FIG. 22) or wave detector
(refer to FIG. 24) is input to the switch circuit 306, a switch is
changed over based on the information of the switch control signal
341.
[0189] Then, a signal (i.e., a reception signal 340) based on the
charge information detected by the charge amplifier 303 is input to
either one of the AD converter 310, 311 or 312 based on a
changeover destination of the switch circuit 306. The AD converter
310, 311 or 312 converts the input analog signal into a digital
signal. The converted reception signal 340 is input to, and stored
in, the storage apparatus 313, 314 or 315 corresponding to the
converter 310, 311 or 312.
[0190] Then, an operator uses the operation unit 323 for selecting
as to which aspect of the reception signal is to be displayed,
prompting an output of a switch control signal 345 from the
operation unit 323 to be input to a switch circuit 361. Either of
the selection terminals 361a, 361b, 361c, 361d, 361e, 361f, 361g,
361h or 361i is turned On in the switch circuit 361 based on the
switch control signal 345, resulting in operating an arithmetic
operation process circuit connected to the turned-On selection
terminal.
[0191] Meanwhile, a control signal for memory device 342, 343 or
344 is generated based on the signal from the operation unit 323.
The storage apparatus 313, receiving the control signal for memory
device 342, outputs the stored reception signal (named as "S1"
hereinafter) of the state 1 to the distributor 351. The storage
apparatus 314, receiving the control signal for memory device 343,
outputs the stored reception signal (named as "S2" hereinafter) of
the state 2 to the distributor 352. The storage apparatus 315,
receiving the control signal for memory device 344, outputs the
stored reception signal (named as "S3" hereinafter) of the state 3
to the distributor 353.
[0192] Then, the signal output from each of the storage units 313
through 315 is processed by an arithmetic operation by the
arithmetic operation process circuit, output as an arithmetic
operation process signal 346 by way of the switch circuit 361, and
input to the image converter 324. The operations thereafter are the
same as those of the second embodiment.
[0193] The next description is on each arithmetic operation in the
case of each of the selection terminals 361 being turned On.
[0194] [Case 1] In the case of the selection terminal 361a being
turned On, the signal S1 output from the distributor 351 is output
as an arithmetic operation process signal 346.
[0195] [Case 2] In the case of the selection terminal 361d being
turned On, the signal S2 output from the distributor 352 is output
as an arithmetic operation process signal 346.
[0196] [Case 3] In the case of the selection terminal 361i being
turned On, the signal S3 output from the distributor 353 is output
as an arithmetic operation process signal 346.
[0197] [Case 4] In the case of the selection terminal 361b being
turned On, the signals S1 and S2 output from the distributors 351
and 352 are input to an arithmetic operation process circuit 354.
The arithmetic operation process circuit 354 performs an arithmetic
operation of S4=S2-S1 for generating a signal S4. And the generated
signal S4 is output as an arithmetic operation process signal
346.
[0198] [Case 5] In the case of the selection terminal 361f being
turned On, the signals S1 and S3 output from the distributors 351
and 353 are input to an arithmetic operation process circuit 355
which then performs an arithmetic operation of S5=S3-S1 for
generating a signal S5. And the generated signal S5 is output as an
arithmetic operation process signal 346.
[0199] [Case 6] In the case of the selection terminal 361h being
turned On, the signals S2 and S3 output from the distributors 352
and 353 are input to an arithmetic operation process circuit 356
which then performs an arithmetic operation of S6=S3-S1 for
generating a signal S6. And the generated signal S6 is output as an
arithmetic operation process signal 346.
[0200] [Case 7] In the case of the selection terminal 361c being
turned On, the signals S4 and S5 generated at the arithmetic
operation process circuits 354 and 355 are input to an arithmetic
operation process circuit 357 which then performs an arithmetic
operation of S7=S4+S5 for generating a signal S7. And the generated
signal S7 is output as an arithmetic operation process signal
346.
[0201] [Case 8] In the case of the selection terminal 361e being
turned On, the signals S5 and S6 generated at the arithmetic
operation process circuits 355 and 366 are input to an arithmetic
operation process circuit 358 which then performs an arithmetic
operation of S8=S5+S6 for generating a signal S8. And the generated
signal S8 is output as an arithmetic operation process signal
346.
[0202] [Case 9] In the case of the selection terminal 361g being
turned On, the signals S4 and S6 generated at the arithmetic
operation process circuits 354 and 356 are input to an arithmetic
operation process circuit 359 which then performs an arithmetic
operation of S9=S4+S6 for generating a signal S9. And the generated
signal S9 is output as an arithmetic operation process signal
346.
[0203] Each arithmetic operation process is described in detail at
this point. The alpha-numerical S1 is noise data related to
measurement data (i.e., a noise or fluctuation stemming from a
transducer (including a drive signal) occurring in association of
an ultrasound transmission) at an ultrasonic anechoic cell 270
shown in FIG. 20 (i.e., the state 1) for example, and the noise
stemming from the transducer includes a crosstalk vibrational wave
related to an in-plane transverse wave propagation unique to the
c-MUT and a standing wave.
[0204] The S2 is reception ultrasound data in the process of
inserting the ultrasonic transducer into an endo cavity as shown in
FIG. 21A (i.e., the state 2) and it corresponds to a surface
reflection signal from a luminal wall of an endo cavity by using a
noncontact aerial ultrasound. This signal also includes a noise
signal related to a noise and fluctuation stemming from the
transducer. Therefore, the arithmetic operation of "S4=S2-S1" can
remove the noise signal.
[0205] Next, the S3 is data including deep diagnosis measurement
information in the case of the transducer fixing and in contact
with a luminal wall surface as shown in FIG. 21B (i.e., the state
3) and it corresponds to a deep reflection signal. This signal
includes signal components of the S1 and S2. In this case the S1
signal is a noise signal, needing to be removed and therefore the
arithmetic operation and therefore the arithmetic operation of
"S5=S3-S1" is performed.
[0206] Meanwhile, since the S2 signal includes a noise signal,
there is a case of an arithmetic operation of "S6=S3-S2" being
suitable; it results in, however, removing also a surface
reflection signal of a luminal wall included in the S3
simultaneously. Such a signal process has a shortfall of losing
information on an organization of a luminal wall surface of an endo
cavity on one hand, while it has an advantage of providing a better
view of a deep diagnosis image as a result of deleting the
information on the organization of the luminal wall surface on the
other hand. As such, whether using "S5=S3-S1" or "S6=S3-S2" is a
discretion of the operator. This method leads to improving a
freedom of diagnosis.
[0207] Note that the "S7=S4+S5", being a result of adding a surface
reflection signal from a luminal wall with a noise being removed
and a deep diagnosis signal with a noise being removed, enables a
uniform diagnosis from the surface to deep part. Also the
"S8=S5+S6" and "S9=S4+S6" make it possible to obtain images taking
advantage of benefits of the respective signals.
[0208] Incidentally, there is a case of the operator being
interested in knowing "how the original signal was", and the
capability of detecting by selecting single signals S1, S2 and S3
is provided by the equipment of the switch circuit 361. Although
the present embodiment does not describe a signal process after the
control signal for memory device 343 in detail, it enables a
display of a separate window in a monitor screen, for example, that
is a display apparatus.
[0209] Also, the present embodiment is configured to calculate the
difference between the input two signals at the arithmetic
operation process circuits 354, 355 and 356; a correlation function
(e.g., a cross-correlation and an autocorrelation), however, may be
used as in the case of the second embodiment.
[0210] Furthermore, the c-MUT is responsive to a Doppler signal
control and harmonic imaging, and the ultrasonic diagnosis system
of the present invention is applicable thereto.
[0211] As described above, various pattern of signal process can be
carried out based on an ultrasound reception signal obtained in
each state selected by the operator. This makes it possible to have
a generated ultrasonic diagnosis image comprise a characteristic
corresponding to the signal process, thereby enabling a multiple
aspects of diagnoses.
[0212] The present invention eliminates a necessity of decreasing a
ratio of an area size of cell zone to the entirety for a c-MUT
featured with trenches on both ends of an element, thereby
eliminating a possibility of decreasing an output of the ultrasonic
transducer.
[0213] Also, the present invention enables a transmission and
reception of an ultrasound in the state of an ultrasonic transducer
contacting with an endo cavity wall and not contacting therewith,
and also a transmission of the reception signal of the received
ultrasound in each state to a corresponding channel by detecting
the state of the ultrasonic transducer.
[0214] Moreover, the present invention enables a buildup of an
ultrasonic diagnosis image related to a contour while inserting an
ultrasonic endoscopic scope equipped with a same c-MUT regardless
of it contacting or not contacting with an endo cavity wall, and
also a buildup of an ultrasonic diagnosis image related to a
cross-sectional image when reaching at a diagnosis region and being
fixed in contact therewith. And, a noise component caused by a
standing wave is removed from the thusly buildup ultrasonic
diagnosis images.
* * * * *