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DESCRIPTION JPS61105463

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DESCRIPTION JPS61105463
[0001]
Visualization of sound image planes has been the subject of extensive research, and as a result,
various methods have been proposed for converting the pattern of the sound pressure surface in
the fluid into a similar visible pattern. To date, a number of ultrasound imaging methods have
been devised which rely on the sensitivity to sonic radiation of either light-sensitive milking or
certain chemical reactions. However, their sensitivity is low (about 111 / cd) and exposure times
of several minutes to several hours are required. A number of secondary effects (such as
luminescence, changes in color or conductivity) of the sound energy absorbed by the insonifled
surface have been exploited to produce both temporary and permanent images. These techniques
are roughly one step more sensitive than their predecessors, but they are still too insensitive for
practical diagnostic visualization. A slightly more sensitive but less responsive method is the
optical scatter detection of the orientation induced by the ultrasonic field in the metal platelet
suspension. An acoustic imaging method that has gained widespread public attention in recent
years is a method based on piezoelectric conversion of instantaneous sound pressure to a
proportional potential. A two-dimensional ultrasonic pressure cover in the fluid can be detected
with high sensitivity by mechanically scanning a small piezoelectric probe (probe) over the fluid
region through which sound passes. In each of the above methods, real time ultrasound
visualization is hindered due to the long exposure or scan time. Real-time visualization is, of
course, extremely important in medical applications. For example, it can be of considerable
benefit to the diagnostician that the organs can be observed continuously as their appearance
changes, or as potassium patients, which are possible with some organs, move the organs by the
action of muscles. To get this we need a real-time conversion method. The optical Bragg
diffraction method (in fact it is not just an image plane conversion method, as this obviously
embodies another imaging principle. ) Has the potential for very high resolution. However, this is
impractical for use at the low MHz frequency required for diagnosis. The liquid surface relief
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method has shown greatly improved image fidelity and sensitivity. However, in the current state
of the art, the sensitivity is still limited for diagnostic purposes and a sufficient dynamic range for
this application has not been obtained, image conversion techniques with laser interference
meters are particularly suitable for their potentially high sensitivity and large image area. There
is a prospect for
However, they too do not achieve sufficient sensitivity, yet lasers and other optical components
require a large stable platform which can not be inserted into a small camera device. Another
possibility is a mokoloff tube, which consists of a resonant quartz face plate on an electron beam
scanning tube. Despite considerable effort to improve it, this Zocograf tube is still lacking in
sufficient resolution and sensitivity, and has problems with nobility. 1: The best approach to realtime visualization of the sound field appears to be to provide a series of discontinuous piezoreceptive elements that are sequentially sampled synchronously with the cathode ray tube
display by means of an electrical gating circuit. Ideally, the number of acceptance elements for a
rectangular matrix that fills the entire image plane would be 40.0007'l to 100.000, but an equal
number of electronic switches and amplifiers could be made for practical use and limited cost.
The task of attaching the above-mentioned receiving element in a given space is beyond the level
of the prior art. However, a hybrid consisting of a linear array of discontinuous piezoelectric
elements that can be scanned electronically at high speed while the entire scan line is
mechanically translated across the image plane, or the sound image field can be moved past the
stationary array. Good compromises can be obtained by using a converter. For a converter using
such a general idea, the Journal of ths Acoustical Society of America, Vol. 44, P. & L 6. 1968 Dec.,
pp. 1719 to 1730 (Page 172. 1727) p, s, Green, J, L, S, Verin and C, C, Norman, "Axic Imaging in
a Tarpin Underwater Environment (Acoustie Imagingin a Turbid)". UnderwaLsr Environscu + t) J.
The present invention provides an ultrasound transducer with an array of piezoelectric elements
in a direct arrangement to convert a compressed sound image field or a compressed sound image
field into electrical pulses. This row comprises segments of piezoelectric material in a support
slot provided in a length of metal plate and by providing the material with fine cuts
perpendicular to the support slot to form isolated areas of a plurality of piezoelectric elements ,
Made from one or more assemblies.
Each isolated area is provided with an electrical contact connected to the utilization circuit. In the
preferred embodiment, the slots in the support member are filled with a material that provides
an impedance match between the piezoelectric material and the medium transmitting the
compressed sound field. In further refinements, an ultrasonic cylindrical lens may be attached to
the support structure along the support slot intermediate the piezoelectric material and the
compressed sound field to spread the sensitivity pattern, thereby bringing smaller rows of
piezoelectric elements closer together for resolution. Improve. An important object of the
invention is to provide means for converting at least a portion of the sound field into electrical
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pulses. Another object of the present invention is to provide a means for impedance matching the
piezoelectric material of the above array and the imaged sound field transmission medium.
Another object of the present invention is to provide focusing means for correcting the size
imbalance of the image conversion segment and sound image field of the piezoelectric element
array. The novel features which are believed to be characteristic of the present invention will be
further described in detail with reference to the attached drawings, which will be described in
detail in the appended claims. FIG. 1 shows a preferred embodiment of a transducer assembly 10
using the transducer of the present invention. As will be described in more detail in connection
with FIGS. 2 and 4 in particular, the array of piezoelectric elements which convert the
compressed sound field into electrical pulses is in slots 11 which extend the entire length of the
transducer assembly 10. It is held. The linear array is given the form of an arc, thus being better
adapted to a single line traversing the compressed sound image electrostatic. But it can function
as well when it is actually in linear form. The reason why the rectilinear array (given the form of
an arc) is better matched to the compressed sound image field considered here than the
rectilinear array in the form of a straight line is here by name The lens used to focus the sound
image in the particular application being proposed is because it provides a focused compressed
sound field in the form of a segment (segment) of the sphere; ie, a portion (segment) of the
sphere It is because the single line which crosses makes an arc. Thus, for a focused compressed
sound field which is focused in the form of a sphere, it is better adapted to the focused
compressed sound field by arranging a linear array of piezoelectric elements on the arc on the
sphere. First, an edge surface view of one piezoelectric plate 16 is shown in FIG. 2 and a plan
view is shown in FIG. 3 for considering the row of metalized piezoelectric material for each
assembly 12. A series of 15 mils wide on the center of 30 mils across the piezoelectric plate
which in this example is 23 mils (1 mil is 0.001 inch) thick, 0.96 inch long, 0.43 inch wide in the
piezoelectric plate dimensions The grooves 18 are cut out and the array itself is formed from a
series of 15 mil wide islands 20 which extend across the entire length of the piezoelectric plate
16.
Thus, these isolated areas are 15 mils wide, 0.43 inches long and are held with the lower
(bonded) portion of the piezoelectric material about 5 to 8 mils thick. Each piezoelectric plate 16
is cut out so that the same number of slot grooves as 32 isolated regions 20 are formed. As can
be seen here, only the isolated region 20 is formed at one end of the piezoelectric plate, and only
the slot 18 is formed at the other end, so when combining the piezoelectric plate assembly, the
isolated region and the slots extend over the entire length of the array. Are arranged alternately.
In order to make a good electrical connection of the piezoelectric array, a good conductor, eg a
coating of silver etc., is applied on both sides of the piezoelectric plate 16 before the slots 18 are
cut out in the piezoelectric plate. The slots 18 are cut away to effectively separate the conductors
on the top surface of the isolated area 20 so that the isolated areas are individually connected to
the electrical circuitry. In order to best understand the support mode of the plate 16 made of a
piezoelectric material, the back surface of the piezoelectric plate 16 according to the ultrasonic
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transducer of the present invention shown in FIG. 4 and the enlarged perspective view of FIG.
Please refer to the partially cut I9i green view. The support of the piezoelectric plate 16 extends
over the entire length of the metal, as can be seen from FIG. 0, which here is formed by a length
of metal strip 30 with support slots 32 over the entire length. Therefore, although it can be
regarded as two pieces, for convenience and its configuration aspect, this is regarded as provided
only on one side. In order to provide support to the piezoelectric plate 16, a portion of the slot
extends from the back side only to a portion of the length of the metal, and a heli 34 is provided
on each side of the slot, thereby allowing the piezoelectric plate 16 to be landed on each heli It
locks over its entire length and mates with the top surface of the isolated area 2- “0” which
makes the back of metal strip 30 equal in height. The wider portion of the slot 32 has the same
width (0, 43 inches) as the piezoelectric plate 16 and the head on the heli 34 is approximately 15
mils wide. Piezoelectric Fi 16 is held in slot 32 by epoxy glue. When the piezoelectric plate 16 is
stuck into the slot 32, the glue will interface with the electrical connection between the
conductive coating 17 on the front side of the piezoelectric plate and the metal support member
(metal strip) 30. Thus, as best seen in FIG. 5, a conductive coating (gold etc.) 36 is applied to the
edge 34 of the metal support (strip) 30 on the conductive coating 17 on the face of the
piezoelectric plate 16 and on both sides of the slot 32. It is preferred that at least a portion be
extended. An impedance matching material is adhered to the surface of the piezoelectric plate L6
in the slot 32 so that energy is best transmitted between the incident compressed sound image
field and the piezoelectric plate 16.
The width of the slot 32 is equal to a number of wavelengths of the detected ultrasound
frequency in the conducting medium. Here, the slot is 0.4 inches wide (dimensions between
helicopters 34), the impedance matching material 40 filling the slot is chosen such that its
impedance is equal to the square root of the impedance product of the piezoelectric ceramic and
the conductive medium And thus form an impedance matching portion. Examples of suitable
matching materials are epoxy or polystyrene mixed with tungsten or aluminum powder to obtain
proper impedance. The thickness of the impedance matching material is the same as that of the
metal support plate (strip) 30, i.e. one quarter wavelength of the detected ultrasound frequency
(in the matching material), the thickness of the matching material in the example under
consideration here Is 8 mils and its mix is 58% (wt%) tungsten powder and 42% epoxy, this epoxy
is made of Shell Oil Company I! The resulting acoustic impedance may be of the type
commercially available under the tradename pon 828. It is lkH / rd / s. Each piezoelectric
isolation region or element 20 forms one sampling element of the entire sampling array, the
sampling along a single line at a rate of one element at a time, at a rate of one element at a time,.
The adjacent line of □ 11 is scanned. In this way, the sound field is reproduced with the best
quality if the sampled segments are well occluded or combined. The way to achieve this is to
form each element of the sampling array equal in height and width, ie a square element.
However, according to the actual configuration techniques used today, the elements 20 of the
array will exceed the width), so to correct this imbalance the slots 32 of the transducer array A
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cylindrical sighting lens 3 is placed over the length and parallel to it at a distance away from the
transducer array by such a distance that the converging incident sound field can be focused on
the array plane in a direction parallel to said cylindrical lens. Proper separation of the aiming
lens 38 and the elements 20 of the transducer array 16 is obtained by extending the lens fixing
spacers 39 on both sides of the length of the support slot 32 and on the upper surface of the
metal support 30. The lower edge of the spacer 39 is fixed to the upper surface of the metal
support 30 by bonding, and the upper edge chamfered over the entire length so as to fit on the
curved surface of the lens 3B is bonded to the lower surface of the lens. In this manner, the
spacer 39 holds the lens 38 on the element 20 of the piezoelectric plate 16 in the proper spaced
relationship.
The material of the spacers 39 is not critical, nor is the distance between the spacers, unless they
are sufficiently separated from the edge of the slot 32 holding the piezoelectric plate 16 so that
they must not interfere with the incident compression sound field. ffi not necessary. FIGS. 6 and
7 illustrate the use of a lens to focus the convergent sound field in one set of planes and to aim
the convergent sound field in another set of planes. That is, FIG. 6 shows that by means of the
convergence line 37, the convergence sound field which is on a plane substantially along the
vertical dimension of the piezoelectric elements 20 of the array 16 passes the lens 38 and the
elongated surface of the array 16 due to the curved surface of the cylindrical lens. It is
schematically shown to be aimed in a plane generally along the longitudinal dimension of the
piezoelectric element 20 (ie perpendicular to the longitudinal axis of the aiming lens 38). Figure
7 on the other hand! As can be seen from the incident convergent sound image field indicated by
the schematic% equation% line 41 that the convergent sound image field substantially located on
the plane along the longitudinal axis of the aiming lens 38 is converged by the arrow 41 and the
arrow. Is first accelerated when it encounters the aiming lens 3B (indicated by the inward
bending of the line in the lens 38), which is the material of the lens, in which the surrounding
sound transmission medium Because the sound speed is higher than in As the sound waves exit
the lens 38 from the lens 38, the velocity is reduced again and so they converge again at their
original angle of incidence (shown by line 43), the aiming lens 38 focuses the sound waves into
the surface of the piezoelectric element 200. It is separated from the piezoelectric element 20 of
the piezoelectric plate 16 by a distance necessary to The lens is convex in cross-section parallel
to the height of the isolated area 20 (i.e. across the slot 32) if the sound velocity is made of a
material higher than the surrounding sound transmission medium, but the longitudinal
dimension of the slot 32 In any cross section parallel to. In practice, the corrector lens (the
aiming lens) 38 may be made curved on one side and fit into the entire transducer assembly 10
over the entire length of the slot 11, or may be made into segments and made into a single
assembly Covering slot 32 for 12 and chamfering its end (not shown), combining the individual
assemblies 12 to form an entire single transducer assembly 10 effectively forms a single lens
You may In some cases, for example, in the case of a square array element rather than an
elongated array element, no lens is required, and thus the lens is not shown in the full assembly
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view of FIG. 1 or the separate assembly 12 of FIG. .
The electrical connection between the front side of the array of piezoelectric elements 20 and the
metal strip 30 is made by a conductive cement or a gold coating 36 as described in connection
with FIG. A pair of printed circuit boards 42 on the back side of the metal strips 30 of each
discrete assembly 12 located on the opposite side of the piezoelectric plate support slot 32 as
part of a means for making electrical connection to the silver coating 17 on the back of the EK
standing area 20. .44 (FIG. 4) are bonded and their edges extend on both sides of the
piezoelectric plate 16 so that the edges of the piezoelectric plate 16 are between the edge 34 of
the metal strip 30 and the printed circuit board Be done. The sides of the printed circuit board
42.44 bonded to the back side of the metal strip 30 are nonconductive. Both sides of the zero
circuit board 42.44 have etched conductive material and a pair of conductive fingers (circuits 46.
46a on the plate 42, 47. 47a) on the circuit board 44 extend over the isolated area 20 in the
piezoelectric plate 16 and the circuit board parallel to the slot 1B and fitted to the isolated area.
Thus, the same number of conductive fingers (32) as the number of isolated regions 20 on the
piezoelectric plate 16 is provided on each circuit board 42.44. Every other finger on each board
is made by a small lead cotton 48 ultrasonically bonded to every other finger on the connected
board and to the silver coating 17 on the back of every other piezoelectric element 20 The
contact fingers on the circuit board 42 (circuit board shown on the left side of FIG. 2) connected
to every other isolated area (piezoelectric element) 20 are for convenience and clarity also
reference numeral 46a; The contact fingers on 44 (the circuit board shown on the right of FIG. 2)
are labeled 47a. The contacting fingers are directly combined with the contacting piezoelectric
element 'l-20 so that the contact conductive fingers 46a on the printed circuit board 42 are
directed directly to the non-conductive fingers 47 on the printed circuit board 44 and also the
printed circuit board The contact at finger 478 on 44 is directly associated with the nonconductive finger 46 on the printed circuit board 42. The nonconductive fingers 46. 47 on both
printed circuit boards provide a means for shielding the contact leads (fingers) 46a, 47a that are
part of the active circuit. In order to obtain a shielding function, the non-contacting fingers 46 on
the printed circuit board 42 are all in contact with the conductive strip 50 (to form a single
conductive element), which is the outer periphery of the printed circuit board (away from the slot
32). Formed by this extending along the side) The radish shield has a comb-like appearance. The
shield is completed by providing conductive leads 52 which are ultrasonically bonded to both the
back side conductive strip 50 on the comb shield and the closest adjacent portions of the support
metal strip 30.
Similarly, the active circuit leads 47a on the printed circuit board 44 are shielded by providing
the conductive strips 54 along the outer periphery of the printed circuit board 44, said outer
periphery contacting the remaining fingers 47 on the circuit board and combing It is
ultrasonically bonded to the conductive strip 54 and the metal strip 30 on the conductive
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structure and is connected to the closest adjacent portion of the metal strip 30 by means of a
diode 56. In this way, the comb-like conductive structures on both printed circuits 42.44 are
effectively connected to ground potential to form a faraday shield, which shields the interference
between the conductive leads 46a, 47a of the active circuit. Prevent the amp. The individual
transducer assemblies 12 must be joined together rigidly to avoid the possibility of breakage of
the piezoelectric transducer plate (piezoelectric plate) 16, and the assembly 12 can be accurately
and rigidly combined to hold the transducer assembly It is necessary to form the whole threedimensional lO. A channel-shaped prefabricated member 58 (see FIG. 5) is provided to open the
two sides of the metal strip 30 and extends to the back side of the piezoelectric plate 16 with its
channels on the slots 32 in the metal strip 30. And it is made to extend parallel to this. Since the
supporting member 58 is made of a non-conductive material such as plastic, it does not interfere
with the conductivity in the conductive finger on the printed circuit 42.44, the leg of the chan is
here glued with epoxy, cement Is rigidly attached to the printed circuit board. The back side of
the bridge-like support member 58 to provide a means for connecting the discrete assembly 12
to the arched assembly support member or shoe 14 for the entire transducer assembly 10 and to
provide a means for securing some of the electronic circuitry to the assembly. An aluminum
block 60 is fixed to the housing by bolts 62. This support arrangement, i.e. the two piece
aluminum block 60 and the support plate 58, is used rather than a single large block or channel
for practical reasons which are considered unimportant. For example, the bridge member 58
must be nonconductive, but the entire block need not be nonconductive. Aluminum is a light,
relatively inert material) and provides a strong enough support, and the assembly is easy to
handle physically if it is made in two parts. That is, the individual assembly 12 can be assembled
more easily. As described above, the aluminum support block 60 is supported by the arched
support shoe 14 and attached to the shoe by the port 64 which penetrates the arched shinny and
extends to the back of the aluminum block.
Also supported by the aluminum block are four printed circuit boards 66, each supporting four
pre-amplifier elements (32 pre-amplifiers in total) and four bodies . Two of the preamplifiers are
supported on each side of the aluminum block and from there the printed circuit l! On the back
of the conductive metal strip 30! It extends downward toward 42.44. The printed circuit boards
on each side of the aluminum block are mounted parallel to one another. An insulating block 61
(112) is provided between the inner printed circuit board 66 and the support block 60, and a
spacer / insulating block 70 is provided between the inner printed circuit board 66 and the next
outer preamplifier board. ing. In order to electrically connect between the preamplifier on
printed circuit board 66 and the conductive fingers on printed circuit board 42.44, conductive
strip 72 is pre-amplifier 66 extends over the circuit. In this manner, the electrical signals
generated by each of the legs of the piezoelectric array on each individual conversion assembly
12 are sent to the individual preamplifiers on the printed circuit board 66 through the
conductive fingers 46 and the conductors 72. Each printed circuit board 66 is provided with an
individual socket 76 which receives conductors carrying the amplified electrical signals
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indicative of the compressed sound image plane to further amplify or utilize those electrical
signals. The precision preamplifier circuit used is of the conventional type and is not part of the
present invention, so any suitable preamplifier or amplifier is described for any elementary text
not shown here. There is. Although specific embodiments and structural arrangements have been
described above, it will be appreciated that the present invention can make many modifications
to the arrangement of materials, structural elements and circuit elements, and so on. " It is
believed that the appended claims, including but not limited to, include any modifications within
the spirit and scope of the present invention. “Compressed sound image field” includes an
acoustic lens, an acoustic mirror, and other acoustic focusing points of an acoustic optical system
(acoustic optical system), and an acoustic counterpart of an enlarged sound source
(acousHccounterpart) It refers to the geometric space shape that is. Each point of the object to be
imaged has a corresponding point in the geometric spatial shape or compressed sound field.
[0002]
Brief description of the drawings
[0003]
1 is a perspective view of an ultrasonic transducer assembly constructed in accordance with an
embodiment of the present invention, FIG. 2 is a cut edge view showing a piezoelectric element
configuration, and FIG. 3 is an edge view of FIG. Figure 4 is a cut-away end view of the
piezoelectric element at an equal scale, and Figure 4 is a perspective view of the back of a portion
of one element of the transducer assembly showing the arrangement of the piezoelectric
elements, the support structure of those elements and the electrical connection FIG. 5 is an
enlarged partial cutaway end view showing the mounting method of the piezoelectric element
and / or the angular rage pattern of the piezoelectric element array according to one
embodiment of the present invention. FIG. 6 is an enlarged and partially cut end view of FIG. 5
showing the lens element expanded in the direction in which the imbalance between height and
width is compensated, but only the edge of the piezoelectric material and the lens In particular in
a plane which approximately corresponds to the elongated dimensions of the individual
elongated elements of the transducer array. Shows the aiming effect of the lens that converges
the compressed sound image field, and FIG. 7 is a view looking down on the top surface of the
transducer array (piezoelectric plate) and the lens element, again showing only the piezoelectric
material and the cylindrical lens. 8 also shows the focusing effect of the lens on the incident
compressed sound image which converges substantially in a plane orthogonal to the longitudinal
direction to the elements in the piezoelectric element array, and FIG. 8 is a side view taken along
line □-in FIG. And shows a method of connecting all the elements of each piezoelectric element
array support assembly.
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lO.. - transducer assembly, 11 and 18 ° 32 ... - slots (grooves), 16 --- m-piezoelectric plate, 17 ...
conductive coating, 20 - - isolated area (element 22 · · · · · Piezoelectric elements, 30-· · Metal
strips (metal support members), 38-· · Same cylindrical aiming lens, 39----Lens fixed spacer, 40 ·m-- · Impedance matching material, 42.44 · · · · · Printed circuit board, 46.47 ·-Nonconductive
fingers, 48.56 · · · · · Small lead, 50.54 · · · Curved-conductive strip, 58-----Channel type bridge
member, 60 ..... Curved aluminum block, 66------Preamplifier Board, 68-----... Insulating block, 76---Individual socket. Name of the agent Kawahara 1)-Ho 'Fx [J1 2 5
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