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JPS5586287

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DESCRIPTION JPS5586287
DESCRIPTION OF THE PREFERRED EMBODIMENTS Method of Producing Ultrasonic Transducer
1) Next Step: (a) Two Focus Widths (FB) and Focal Distances (FA) in Focus Related Amounts to be
Provided in advance (A) For example, determine the outer dimension (2aO) of this diaphragm in
relation to the radius of curvature of the ultrasonic diaphragm with respect to FB) or determine
the radius of curvature in relation to the outer dimension (2ao), (b) then (C) determining the
outer radius determined in steps (a) k and (b) to determine the central radius of the curvature
radius and outer dimensions of the diaphragm with respect to the other focal relation amount
(e.g. FA) The maximum value of the opening angle of the ultrasonic field behind the focal point
given by the radius of curvature is set to a value that can obtain the optimum ratio of the
opening angle of the ultrasonic field and the side beam by making the active surface of the
ultrasonic diaphragm empty. Equipped with at least one ultrasonic diaphragm, characterized in
that it is performed according to There are voids on the active surface of the diaphragm that is
focused by the aid, and the focal length, focal width and focal angle of the generated ultrasonic
field can be determined in advance. Method of manufacturing an acoustic transducer. 2) The
outside dimension (2a □) of the ultrasonic diaphragm is an ultrasonic wave.
2, the scope of claims
8. Detailed description of the invention The present invention provides an ultrasonic diaphragm
in which the active surface for generating a focused acoustic field is provided with an air gap by
auxiliary means (iig, focal distance of focal spot, focal width and focal point behind focal spot).
The present invention relates to a method of manufacturing an ultrasonic transducer
(transducer) in which the opening angle of .alpha. In the field of ultrasound application,
particularly in the field of medical electrical or material testing, it is desirable to make the
ultrasound field created by the ultrasound diaphragm as purposeful as possible. For example, the
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focal length of the focusing field needs to be as close as possible to the distance from the
diaphragm surface to the inspection point. In addition, the focal radius, (b) radius of curvature R
of the acoustic field is R = G (FA. (4) There is also a need to enhance disassembly. It is also
required to minimize the influence of the side beam of the acoustic field. All of these conditions
have to be fulfilled for any purpose, for example when using ultrasound equipment without a
prechannel. In the conventional manufacturing method of ultrasonic transducers, it is impossible
to uniquely set the desired optimum relationship between the focal length, focal width and
opening angle of the acoustic field. In the process described in "J'oural of Acoustical 5 ociety of
America", 44 + 5 + 196 Sep 1310-1818, it is not possible to define these focusing quantities
separately and to change them. The ultrasonic vibrator it produced by this method is used only
for continuous oscillation and is unsuitable for pulse echo operation. In the case of pulse echo
operation, the focal length and the focal width or opening angle automatically increase. In the
case of ultrasonic vibrators, the lateral resolution can be increased by minimizing the focal length
and the angle of divergence of the acoustic field behind the focal point. It is well known that a
small opening angle can be achieved by reducing the curvature of the EndPage: 2 fish section.
However, as the active surface is expanded or the curvature reduced, the acoustic field is spread
behind and behind the focal field and the lateral resolution in the examination area behind it is
degraded. If this method is not adopted, the lateral resolution will be improved directly at the
focal point if the focal plane is made smaller or the focal plane is artificially intensified, but it will
be sharply deteriorated at the back because the opening angle is large. Besides this, it has also
been proposed to achieve good lateral resolution near the focal point by strongly focusing the
vibrator as a spherical surface, but the divergence angle becomes extremely large behind the
focal point and the lateral resolution is also proposed. Drops sharply. The area with high lateral
resolution is thus reduced to a very small examination area.
It has also been proposed to make the vibrating body annular. Annular oscillators are
advantageous for the formation of interference structures, which result in relatively strong
focusing and small opening angles and high lateral resolution. However, as the interference
structure advances, the side beams are created. The object of the present invention is to select an
ultrasonic transducer so that the effect of side beams is extremely small and the highest lateral
resolution can be obtained even if focal length and focal length are chosen arbitrarily. It is to
make. This object is achieved by producing an ultrasonic transducer according to the following
steps. That is, first, take two focal widths and focal distances in three focal relation amounts
defined in advance with respect to the ultrasonic field generated by the transducer, and in the
first process stage, the radius of curvature of the ultrasonic diaphragm Relatedly determine the
outer dimensions of the diaphragm or determine the radius of curvature in relation to the outer
dimensions. Next, in the second process step, the radius of curvature and the undetermined one
of the outer dimensions of the ultrasonic diaphragm are determined with respect to the other of
the above two focus related quantities. Finally, in the third step, the size of the sky is reduced to
the maximum value of the opening angle of the ultrasonic field given by the outer dimensions
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and radius of curvature so far determined so as to obtain the optimum ratio of the opening angle
and the sub beam. The plaque is provided on the active surface of the ultrasonic diaphragm. m ′
′ e 乍 Δ and 1 core)] First, in the first and second process steps, a molded part as a diaphragm
thick plate whose outer dimensions and radius of curvature are determined In contrast to this,
either through holes are machined or holes are made in the surface contact layer to remove part
of the diaphragm material. Alternatively, the ultrasonic diaphragm may be electrically divided
into several discrete vibrating surfaces so as to electrically block the operation of appropriate
ones of the discrete vibrating surfaces. The invention will be described in more detail with
reference to the drawings and with reference to an embodiment. FIG. 1 shows an annular
ultrasonic diaphragm made by the method of the present invention. The diaphragm 1 is made of,
for example, a piezo ceramic material, and a through hole 2 is provided as a void. A portion of the
contact layer 8 may be removed instead of this through hole. The annular diaphragm is
mechanically bent to have a radius of curvature R. Instead of being a curved diaphragm, it may
be electrically inverted as a plane diaphragm or it may be mechanically bent and electrogenerated by the method of the invention (8) in the production of an ultrasonic transducer
according to the method of the invention The diaphragm is divided into individual segments 4 as
shown in FIG. 2 to give each segment a delay time necessary to bend the ultrasonic surface. The
diaphragm shown in FIGS. 1 and 2 is manufactured according to the present invention as follows.
First, the optimum values of the focal width FB and the focal length FA are determined in
advance according to the intended application field. However, the focal width FB is a function of
the radius of curvature R of the acoustic field forcing surface and the outer dimension (outer
diameter) 2aO of the diaphragm similarly to the focal length FA, and pn = f (R, a □) (1) and FA =
G (R, a □) (2). Rewriting (1), a □ = F (R, FB) (3) or R = F 2 (ao, FB) (4) (2) and (3) a == c (FA, F) R,
FB)) (5) (2) and (4) from a □ = G2 (FA, F2 (a □, FB)) (6) EndPage: 3 to = R / (芋) (7) It is
convenient to find the normalized radius RN. In this case, the normalized focal width FB / ao and
the standardized focal distance FA / (") are determined by the RN completely independently of
the frequency. At the same time, the outer dimension zao is also determined automatically in
relation to RN. The required value of RN can be determined by comparing the predetermined
focus distance 1 [tFA with the value of FA determined in relation to the RN with respect to the
scheduled operating frequency. This also determines the outer dimension 2ao, and the actual
radius of curvature R is determined from the values of RN and 98 □. The maximum value of the
opening angle of the ultrasonic field behind the focal point derived from the values of the
external dimensions and the radius of curvature determined in this way is the size of the void 'l,
& 1 selected on the active surface of the ultrasonic diaphragm. Thus, the ratio of the opening
angle to the side beam can be adjusted to the optimum value according to the application. An
example of the outer diaphragm for the operating frequency f = 3.5 MHl is shown on the right of
FIG. 8 as an example. The radius of curvature is set at R = 242 m. The diagram on the left
represents, from top to bottom, the lateral resolution La (in M units) versus the penetration depth
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Te (in er 11 units) to the measurement point when the sub-beams are-(3 dB, -20 dB and 1 49 dB).
The lateral resolution curve I of the ultrasonic transducer according to the invention has a much
better course than the lateral resolution curves l and 1 of the one made in the conventional
manner in the range of approach depths 0 to 18α in all the diagrams. It is clear to show. FIG. 4
shows the deformation of the ultrasonic diaphragm. In this case, the ultrasonic vibrator is
configured as an assembly 5 in which a large number (for example, 60 to 160) of individual
elements are arranged. In such an aggregate vibrator, some elements are excluded as a group to
form a non-operating surface in order to form a desired ultrasonic image. This element group is
shown as 7 in the figure. The setting of the non-operating surface is performed through an
electronic circuit or mechanically.
In the one of FIG. 4, these system dimensions 9ao = 401! ! The void 8 is made by blocking in the
ring (11) of the through hole diameter 2 ai == 113 w &. This void always spreads in a direction
perpendicular to the direction of the element array. Another end 9 is made mechanically and
extends in the direction of the array of elements. The dimensions 2aO1, 2ail and 2a0212ai1 of
these two vacancies are determined in the third step of the process according to the invention. In
the vibrator of FIG. 4, the electric field change 8 of the group 8 defines the radius of the surface
curve in the zx plane drawn in the figure. The radius of curvature in the zy-plane is
predetermined by the mechanically created air gap 9 and the mechanical curvature of the
element. Instead of mechanical folding, it is possible to employ the folding of the ultrasound
surface by means of electronic circuits for ultrasound field flooding. In this case, the element
array needs to be formed at each matrix point corresponding to the configuration of FIG.
4. Brief description of the drawings FIGS. 1, 2 and 4 respectively use the present invention as a
mixture, for example the elements in group 7 are obtained with the specific dimensions of
electricity (L2) and The lateral resolution curve is shown. In FIG. 1 and FIG. 2, 1 is a diaphragm, 2
is a through hole, 8 is a contact layer, and 4 is a vibration segment constituting a matrix. (6118)
Agent Patent Attorney "Tomimura Kiyoshi EndPage: 4
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