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DESCRIPTION JP2018068620

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DESCRIPTION JP2018068620
Abstract: The present invention provides an ultrasonic device, an ultrasonic probe, and an
ultrasonic apparatus capable of suppressing a reduction in resolution due to tailing. An ultrasonic
transducer array includes an ultrasonic transducer array having a first area in which a first
ultrasonic transducer is provided, and a second area in which a second ultrasonic transducer is
provided. A first acoustic layer 431 stacked in one region, a second acoustic layer 432 stacked in
the second region, and a first acoustic layer and a second acoustic layer provided so as to
straddle the first acoustic layer and the second acoustic layer And an acoustic lens 44 having an
acoustic impedance larger than that of the layer, and in the stacking direction, the first dimension
L1 of the first acoustic layer corresponds to the wavelength of the first acoustic layer of the
ultrasonic wave transmitted by the first ultrasonic transducer. And the second dimension L2 of
the second acoustic layer is a wavelength in the second acoustic layer of the ultrasonic wave
received by the second ultrasonic transducer in the stacking direction. Then, it is n times of λb /
2. [Selected figure] Figure 4
Ultrasonic device, ultrasonic probe, and ultrasonic device
[0001]
The present invention relates to an ultrasound device, an ultrasound probe, and an ultrasound
apparatus.
[0002]
Conventionally, an ultrasonic array configured by arranging a plurality of ultrasonic transducer
elements (ultrasound transducers) for transmitting and receiving ultrasonic waves in an array,
and a protective layer (acoustic layer) provided on the ultrasonic array There is known an
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ultrasonic transducer element unit (ultrasound device) including an acoustic lens provided on an
acoustic layer (for example, Patent Document 1).
[0003]
In the ultrasonic device described in Patent Document 1, the ultrasonic transducer includes a
vibrating film and a piezoelectric element as a vibrator provided on the vibrating film.
The ultrasonic device is configured by sequentially laminating an acoustic layer and an acoustic
lens on a vibrating membrane.
The ultrasonic device transmits and receives ultrasonic waves in a state where the acoustic lens
is in contact with a measurement target such as a living body. For example, the ultrasonic waves
transmitted by the drive of the piezoelectric element are output from the surface of the acoustic
lens into the living body after propagating through the acoustic layer and the acoustic lens.
[0004]
JP, 2014-198197, A
[0005]
Here, in the conventional ultrasonic device as described in Patent Document 1, the acoustic
impedance of the acoustic layer is made larger than that of the acoustic lens, and the thickness of
the acoustic layer is a half value of the wavelength of the ultrasonic wave in the acoustic layer. By
doing this, the influence of the reverberation of the ultrasonic waves can be suppressed.
That is, of the ultrasonic waves, a reverberation component subsequent to the second wave
following the first wave having a large amplitude, a so-called tailing portion, an interface (first
interface) between the ultrasonic transducer and the acoustic layer, an acoustic layer It can
cancel out by the reflected wave (interface reflected wave) which arises in an interface (2nd
interface) with an acoustic lens.
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[0006]
For example, the interface reflection wave generated at the second interface of the transmission
waves from the ultrasonic transducer is reflected at the first interface and reenters the second
interface. At this time, due to the phase inversion at the first interface, the interface reflected
wave overlaps the second wave of the transmission wave in the opposite phase, and the second
and subsequent waves are canceled out. Also, for example, after being reflected at the first
interface, the received wave directed to the ultrasonic transducer is reflected at the second
interface and is incident on the first interface again. Similarly, due to the phase inversion at the
first interface, the interface reflected wave overlaps the second wave of the received wave in
reverse phase, and the second and subsequent waves of the received wave are canceled out.
[0007]
However, in an ultrasonic array capable of receiving an ultrasonic wave of a frequency different
from that of the transmission wave, for example, high-order harmonics of the transmission wave,
when an acoustic layer of the same thickness is provided in the transmission area and the
reception area, There is a possibility that the influence of tailing may become large on the
receiving side. For example, in the case of receiving the second harmonic, the wavelength of the
reception wave in the acoustic layer is half of the transmission wave. Therefore, in the thickness
of the acoustic layer, the half wavelength of the transmission wave corresponds to one
wavelength of the reception wave. Therefore, when the interface reflection of the received wave
generated at the first interface is reflected at the second interface and re-incident on the first
interface, the reflected waves overlap in the opposite phase to the third wave of the received
wave, and the second wave is not canceled. . For this reason, the influence of tailing becomes
greater than that on the transmission side, and the resolution may be reduced.
[0008]
An object of the present invention is to provide an ultrasonic device, an ultrasonic probe, and an
ultrasonic apparatus capable of suppressing a reduction in resolution due to tailing.
[0009]
An ultrasonic device according to an application example of the present invention includes a first
region provided with a first ultrasonic transducer having a first vibrating film, and a second
region provided with a second ultrasonic transducer having a second vibrating film. An ultrasonic
transducer array having a region, a first acoustic layer laminated on the first region of the
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ultrasonic transducer array, and a second acoustic layer laminated on the second region of the
ultrasonic transducer array The ultrasonic transducer, comprising: an acoustic layer; and an
acoustic lens provided across the first acoustic layer and the second acoustic layer and having an
acoustic impedance larger than that of the first acoustic layer and the second acoustic layer. In
the stacking direction of the first acoustic layer with respect to the array, a first dimension of the
first acoustic layer is the first dimension of the ultrasonic waves transmitted by the first
ultrasonic transducer. The wavelength in the acoustic layer is λa and is an integer n times λa /
2, and the second dimension of the second acoustic layer in the stacking direction is the second
of the ultrasonic waves received by the second ultrasonic transducer. The wavelength in the
acoustic layer is λb, which is n times λb / 2.
[0010]
In this application example, the first dimension of the first acoustic layer stacked on the first
region of the ultrasonic transducer array is an integer n times λa / 2.
The second dimension of the second acoustic layer is an integer n times λb / 2.
Thereby, when ultrasonic waves of a frequency different from the ultrasonic wave transmitted
from the first ultrasonic transducer are received by the second ultrasonic transducer, for
example, the transmission wave (fundamental wave) from the first ultrasonic transducer Even in
the case of receiving high-order harmonics to H, the reduction in resolution can be suppressed.
Here, the ultrasonic waves propagating through the first acoustic layer reverse in phase when
being reflected at the interface with the first ultrasonic transducer. Similarly, the ultrasonic
waves propagating through the second acoustic layer reverse in phase when being reflected at
the interface with the second ultrasonic transducer. In this application example, a reflected wave
(second interface) generated at the interface (the second interface) between the first acoustic
layer and the acoustic lens of the ultrasonic waves (the transmission wave and the fundamental
wave) transmitted from the first ultrasonic transducer 1) is reflected by the interface (first
interface) between the first acoustic layer and the first ultrasonic transducer, and then enters the
first interface again. At this time, since the first dimension is (λa / 2) · n, the propagation
distance of the first reflected wave is λa · n corresponding to the round trip of the first acoustic
layer. Therefore, at the second interface, the phase of the first reflected wave is delayed by 2nπ
and opposite to the phase of the transmission wave. Thus, the first reflected wave cancels out the
(n + 1) th and subsequent waves in the reverberation portion of the transmission wave. On the
other hand, among the reflected waves from the measurement object, the reflected wave (second
reflected wave) reflected by the interface (first interface) between the second acoustic layer and
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the second ultrasonic transducer is the second acoustic layer and the acoustic wave. After being
reflected at the interface (third interface) with the lens, the light again enters the second
interface. At this time, since the second dimension is (λb / 2) · n, the phase of the second
reflected wave is similarly delayed by 2nπ and opposite to the phase of the received wave.
Therefore, the second and subsequent reflected waves cancel out the (n + 1) th and subsequent
waves in the reverberation portion of the received wave. From the above, it is possible to offset at
least the (n + 1) th and subsequent waves among the reverberation components of the ultrasonic
wave on either the transmitting side or the receiving side, so that the reduction in resolution due
to the influence of tailing can be suppressed, and the reduction in measurement accuracy .
[0011]
In the ultrasonic device according to the application example, it is preferable that the first
dimension is λa / 2 and the second dimension is λb / 2. This application example corresponds
to n = 1 in the above application example. That is, according to this application example, at least
either the second wave or later of the reverberation component of the ultrasonic wave can be
canceled out on either the transmitting side or the receiving side, and the influence of the tailing
can be suitably suppressed, and the measurement accuracy is degraded. Can be suppressed more
reliably.
[0012]
An ultrasonic device according to an application example of the present invention includes a first
region provided with a first ultrasonic transducer having a first vibrating film, and a second
region provided with a second ultrasonic transducer having a second vibrating film. An ultrasonic
transducer array having a region, a first acoustic layer laminated on the first region of the
ultrasonic transducer array, and a second acoustic layer laminated on the second region of the
ultrasonic transducer array And an acoustic lens provided across the first acoustic layer and the
second acoustic layer and having an acoustic impedance larger than that of the first acoustic
layer and the second acoustic layer, and the second acoustic layer Is located opposite to the first
layer on the ultrasonic transducer array side and the ultrasonic transducer array, and the
acoustic impedance is smaller than that of the first layer A second layer, and in a stacking
direction of the first acoustic layer with respect to the ultrasonic transducer array, a first
dimension of the first acoustic layer is an ultrasonic wave transmitted by the first ultrasonic
transducer; The wavelength is λa and is an integer n times λa / 2, and the dimensions of the
first layer and the second layer in the stacking direction are the second acoustic waves of the
ultrasonic waves received by the second ultrasonic transducer. The wavelength in the layer is
λb, which is an odd multiple of λb / 4, and the dimension of at least one of the first layer and
the second layer is not more than n times λb / 2.
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[0013]
In this application example, the first dimension of the first acoustic layer stacked on the first
region of the ultrasonic transducer array is an integer n times λa / 2.
Also, the second acoustic layer has a first layer and a second layer. The dimensions of the first
layer and the second layer are an odd multiple of λb / 4, and at least one of the dimensions of
the first layer and the second layer is not more than n times λb / 2. Thus, as in the above
application example, when an ultrasonic wave of a frequency different from that transmitted
from the first ultrasonic transducer is received by the second ultrasonic transducer, for example,
the first ultrasonic transducer Therefore, even when high-order harmonics to the transmission
wave (fundamental wave) are received, the reduction in resolution can be suppressed. Here, the
ultrasonic waves propagating through the first acoustic layer reverse in phase when being
reflected at the interface with the first ultrasonic transducer. Similarly, the ultrasonic waves
propagating through the first layer of the second acoustic layer reverse in phase when being
reflected at the interface with the second ultrasonic transducer or the interface with the second
layer. In this application example, as in the above application example, the phases of the
transmission wave and the first reflected wave transmitted from the first ultrasonic transducer
are opposite in phase, and the n + 1th and subsequent waves of the reverberation portion of the
transmission wave are Be offset. On the other hand, the second reflected wave reflected by the
interface (first interface) between the second acoustic layer and the second ultrasonic transducer
among the received waves from the measurement target is the third interface or the first layer
and the second layer. After being reflected at the interface (fourth interface) with the two layers,
when the light is incident on the first interface again, it has an antiphase with the received wave.
In addition, of the received waves, the reflected wave (third reflected wave) reflected at the fourth
interface is reflected by the third interface and then in reverse phase with the received wave
when it is incident on the fourth interface again. Be offset. Furthermore, the dimension of at least
one of the first layer and the second layer is not more than n times λb / 2. For this reason, as in
the above-described application example, at least one of the second reflected wave and the third
reflected wave has a delay amount of 2 nπ or less and an opposite phase with respect to the
received wave. For this reason, at least the (n + 1) th and subsequent waves of the reverberation
portion of the received wave are canceled out. From the above, it is possible to suppress the
decrease in resolution due to the influence of the tailing, that is, the decrease in measurement
accuracy, due to detection of at least the n + 1th wave or later of the reverberation components
of the ultrasonic wave on either the transmission side or the reception side. Can be suppressed.
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[0014]
In the ultrasonic device according to this application example, the dimensions of the first acoustic
layer and the dimensions of the second acoustic layer are preferably the same. In this application
example, the dimensions of the first acoustic layer and the dimensions of the second acoustic
layer are the same. Thereby, the interface with each acoustic layer of the acoustic lens provided
over the 1st acoustic layer and the 2nd acoustic layer can be made into a plane, and the
composition of an acoustic lens can be simplified.
[0015]
In the ultrasonic device according to the application example, it is preferable that the first
dimension is λa / 2, and the dimension of one of the first layer and the second layer is λb / 4.
In this application example, as in the above application example, it is possible to cancel out the
second or later of the reverberation components of the transmission wave. On the reception side,
the dimension of one of the first layer and the second layer is set to λb / 4 smaller than λb / 2
corresponding to n = 1. Thus, in the one layer, it is possible to cancel out at least the second or
later of the reverberation components of the received wave. Therefore, the influence of tailing
can be suitably suppressed, and a decrease in measurement accuracy can be suppressed.
[0016]
An ultrasonic probe according to an application example of the present invention is provided
with a first region in which a first ultrasonic transducer having a first vibrating film is provided,
and a second ultrasonic transducer having a second vibrating film. An ultrasonic transducer
array having a second area; a first acoustic layer laminated on the first area of the ultrasonic
transducer array; and the second area on the ultrasonic transducer array An acoustic lens
provided across the second acoustic layer, the first acoustic layer and the second acoustic layer,
and having an acoustic impedance larger than that of the first acoustic layer and the second
acoustic layer, and the ultrasonic transducer array A housing for containing the first acoustic
layer, the second acoustic layer, and the acoustic lens, and the first acoustic layer of the
ultrasonic transducer array In the layer direction, a first dimension of the first acoustic layer is an
integer n times λa / 2, where λa is a wavelength of the ultrasonic wave transmitted by the first
ultrasonic transducer in the first acoustic layer, and In the stacking direction, the second
dimension of the second acoustic layer is characterized in that the wavelength of the ultrasonic
wave received by the second ultrasonic transducer in the second acoustic layer is λb and n times
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λb / 2 I assume. In the ultrasonic probe of this application example configured as described
above, in the transmission wave and the reception wave as well as the above application example,
the (n + 1) th and subsequent waves of the reverberation portion are canceled out. Therefore, the
reverberation component of the ultrasonic wave can be detected, that is, the reduction in
resolution due to the influence of the tailing can be suppressed, and the reduction in
measurement accuracy can be suppressed.
[0017]
An ultrasonic probe according to an application example of the present invention is provided
with a first region in which a first ultrasonic transducer having a first vibrating film is provided,
and a second ultrasonic transducer having a second vibrating film. An ultrasonic transducer
array having a second area; a first acoustic layer laminated on the first area of the ultrasonic
transducer array; and the second area on the ultrasonic transducer array An acoustic lens
provided across the second acoustic layer, the first acoustic layer and the second acoustic layer,
and having an acoustic impedance larger than that of the first acoustic layer and the second
acoustic layer, and the ultrasonic transducer array And a case for housing the first acoustic layer,
the second acoustic layer, and the acoustic lens, wherein the second acoustic layer is formed on
the side of the ultrasonic transducer array. A layer, and a second layer opposite to the ultrasonic
transducer array and having an acoustic impedance smaller than that of the first layer, and
laminating the first acoustic layer to the ultrasonic transducer array In the direction, the first
dimension of the first acoustic layer is an integer n times λa / 2, where λa is the wavelength of
the ultrasonic wave transmitted by the first ultrasonic transducer, and the first dimension in the
stacking direction is the first The dimensions of the layer and the second layer are such that the
wavelength in the second acoustic layer of the ultrasonic wave received by the second ultrasonic
transducer is λb, and is an odd multiple of λb / 4, and the first layer and the second layer The
dimension of at least one of the two layers is characterized by being not more than n times λb /
2. In the ultrasonic probe of this application example configured as described above, the n + 1th
and subsequent waves in the reverberation portion of the transmission wave are canceled as in
the above application example. Further, at least one of the first layer and the second layer cancels
out at least the (n + 1) th and subsequent waves of the reverberation portion of the received
wave. Therefore, the reverberant component of the ultrasonic wave can be detected on both the
transmitting side and the receiving side, that is, a reduction in resolution due to the influence of
tailing can be suppressed, and a reduction in measurement accuracy can be suppressed.
[0018]
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An ultrasonic apparatus according to an application example of the present invention includes a
first area provided with a first ultrasonic transducer having a first vibrating film, and a second
area provided with a second ultrasonic transducer having a second vibrating film. An ultrasonic
transducer array having a region, a first acoustic layer laminated on the first region of the
ultrasonic transducer array, and a second acoustic layer laminated on the second region of the
ultrasonic transducer array An acoustic lens, an acoustic lens provided across the first acoustic
layer and the second acoustic layer, and having an acoustic impedance larger than that of the
first acoustic layer and the second acoustic layer, the first ultrasonic transducer, and A control
unit for controlling the second ultrasonic transducer, in the stacking direction of the first acoustic
layer with respect to the ultrasonic transducer array, The first dimension of the first acoustic
layer is an integer n times λa / 2, where λa is a wavelength of the ultrasonic wave transmitted
by the first ultrasonic transducer in the first acoustic layer, and in the stacking direction, The
second dimension of the second acoustic layer is characterized in that the wavelength of the
ultrasonic wave received by the second ultrasonic transducer in the second acoustic layer is λb
and n times λb / 2. In the ultrasonic apparatus of this application example configured as
described above, in the transmission wave and the reception wave as well as the above
application example, the (n + 1) th and subsequent waves of the reverberation portion are
canceled out. Therefore, the reverberation component of the ultrasonic wave can be detected,
that is, the reduction in resolution due to the influence of the tailing can be suppressed, and the
reduction in measurement accuracy can be suppressed.
[0019]
An ultrasonic apparatus according to an application example of the present invention includes a
first area provided with a first ultrasonic transducer having a first vibrating film, and a second
area provided with a second ultrasonic transducer having a second vibrating film. An ultrasonic
transducer array having a region, a first acoustic layer laminated on the first region of the
ultrasonic transducer array, and a second acoustic layer laminated on the second region of the
ultrasonic transducer array An acoustic lens, an acoustic lens provided across the first acoustic
layer and the second acoustic layer, and having an acoustic impedance larger than that of the
first acoustic layer and the second acoustic layer, the first ultrasonic transducer, and A control
unit that controls the second ultrasonic transducer, and the second acoustic layer includes a first
layer on the ultrasonic transducer array side, and the ultrasonic wave And a second layer located
opposite to the transducer array and having an acoustic impedance smaller than that of the first
layer, in the stacking direction of the first acoustic layer with respect to the ultrasonic transducer
array. The first dimension of the acoustic layer is an integer n times λa / 2, where λa is the
wavelength of the ultrasonic wave transmitted by the first ultrasonic transducer, and in the
stacking direction, the first layer and the second layer Of the wavelength of the ultrasonic wave
received by the second ultrasonic transducer in the second acoustic layer is λb, and is an odd
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multiple of λb / 4, and at least one of the first layer and the second layer One dimension is
characterized by being not more than n times λb / 2. In the ultrasound apparatus of this
application example configured as described above, the n + 1 th and subsequent waves in the
reverberation portion of the transmission wave are canceled as in the above application example.
Further, at least one of the first layer and the second layer cancels out at least the (n + 1) th and
subsequent waves of the reverberation portion of the received wave. Therefore, the reverberant
component of the ultrasonic wave can be detected on both the transmitting side and the
receiving side, that is, a reduction in resolution due to the influence of tailing can be suppressed,
and a reduction in measurement accuracy can be suppressed.
[0020]
BRIEF DESCRIPTION OF THE DRAWINGS The figure which shows schematic structure of the
ultrasound apparatus of 1st Embodiment. BRIEF DESCRIPTION OF THE DRAWINGS Sectional
drawing which shows schematic structure of the ultrasound probe of 1st Embodiment. The top
view which looked at the element substrate of the ultrasonic device of a 1st embodiment from
the sealing plate side. Sectional drawing which shows typically the cross section of the ultrasonic
device of 1st Embodiment. FIG. 6 is a view for explaining the operation of the ultrasonic device
according to the first embodiment. FIG. 6 is a view for explaining the operation of the ultrasonic
device according to the first embodiment. Sectional drawing which shows schematic structure of
the ultrasonic device of 2nd Embodiment. The figure explaining the effect | action of the
ultrasound device of 2nd Embodiment. Sectional drawing which shows schematic structure of the
ultrasonic device which concerns on a modification.
[0021]
First Embodiment Hereinafter, an ultrasonic measurement apparatus according to a first
embodiment will be described based on the drawings. FIG. 1 is a perspective view showing a
schematic configuration of the ultrasonic measurement apparatus 1. The ultrasonic measurement
device 1 corresponds to an ultrasonic device, and includes an ultrasonic probe 2 and a control
device 10 connected to the ultrasonic probe 2 via a cable 3 as shown in FIG. The ultrasonic
measurement apparatus 1 causes an ultrasonic probe 2 to abut on the surface of a living body
(for example, a human body) to be measured, and transmits ultrasonic waves from the ultrasonic
probe 2 into the living body. In addition, the ultrasonic measurement apparatus 1 receives the
second harmonic of the ultrasonic waves reflected by the organ in the living body by the
ultrasonic probe 2, and based on the received signal, for example, an internal fault in the living
body Acquire an image or measure the state of an organ in a living body (eg, blood flow etc.).
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[0022]
[Configuration of Control Device] The control device 10 corresponds to a control unit, and as
shown in FIG. 1, includes an operation unit 11 including a button, a touch panel, and the like, and
a display unit 12. Further, although not shown, the control device 10 includes a storage unit
configured by a memory or the like, and an operation unit configured by a CPU (Central
Processing Unit) or the like. The control device 10 controls the ultrasonic measurement device 1
by causing the computing unit to execute various programs stored in the storage unit. For
example, the control device 10 outputs a command for controlling the drive of the ultrasound
probe 2 or forms an image of the internal structure of a living body based on a reception signal
input from the ultrasound probe 2 and displays the display unit 12 or displaying biological
information such as blood flow and the like on the display unit 12. As such a control device 10,
for example, a terminal device such as a tablet terminal, a smartphone, or a personal computer
can be used, and a dedicated terminal device for operating the ultrasonic probe 2 may be used.
[0023]
[Configuration of Ultrasonic Probe] FIG. 2 is a cross-sectional view showing a schematic
configuration of the ultrasonic probe 2. The ultrasound probe 2 corresponds to an ultrasound
probe, and as shown in FIG. 2, for controlling the casing 21, the ultrasound device 22 housed
inside the casing 21, and the ultrasound device 22. And a circuit board 23 provided with a driver
circuit and the like. The ultrasonic device 22 and the circuit board 23 constitute an ultrasonic
sensor 24 corresponding to an ultrasonic module.
[0024]
[Configuration of Housing] As illustrated in FIG. 1, the housing 21 is formed in, for example, a
box shape having a rectangular shape in a plan view, and a sensor window 21B is provided on
one surface (sensor surface 21A) orthogonal to the thickness direction. And part of the
ultrasound device 22 is exposed. Further, a passage hole 21C of the cable 3 is provided in a part
of the case 21 (a side surface in the example shown in FIG. 1), and the cable 3 is connected to the
circuit board 23 inside the case 21 from the passage hole 21C. ing. Further, the gap between the
cable 3 and the passage hole 21C is, for example, filled with a resin material or the like to ensure
waterproofness. In the present embodiment, a configuration in which the ultrasonic probe 2 and
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the control device 10 are connected using the cable 3 is exemplified, but the present invention is
not limited thereto. For example, the ultrasonic probe 2 and the control device 10 are wireless It
may be connected by communication, and various configurations of the control device 10 may be
provided in the ultrasonic probe 2.
[0025]
[Configuration of Circuit Board] The circuit board 23 is electrically connected to the first signal
terminal 414 P and the common terminal 416 P (see FIG. 3) of the ultrasonic device 22, and the
ultrasonic device 22 is connected based on the control of the control device 10. Control.
Specifically, the circuit board 23 includes a transmission circuit, a reception circuit, and the like.
The transmission circuit outputs a drive signal that causes the ultrasonic device 22 to transmit
ultrasonic waves. The reception circuit acquires the reception signal output from the ultrasonic
device 22 that has received the ultrasonic wave, performs amplification processing of the
reception signal, AD conversion processing, phasing addition processing, and the like, and
outputs the result to the control device 10 Do.
[0026]
[Configuration of Ultrasonic Device] FIG. 3 is a plan view of the element substrate 41 in the
ultrasonic device 22 as viewed from the sealing plate 42 side. FIG. 4 is a cross-sectional view
including the central portion of the ultrasound device 22. As shown in FIG. As shown in FIG. 4,
the ultrasonic device 22 includes an element substrate 41 provided with an ultrasonic transducer
array 46, a sealing plate 42, and an acoustic layer 43 including a first acoustic layer 431 and a
second acoustic layer 432. And an acoustic lens 44.
[0027]
(Structure of Element Substrate) The element substrate 41 corresponds to a substrate, and as
shown in FIG. 4, includes a substrate main body 411 and a vibrating film 412 provided on the
sealing plate 42 side of the substrate main body 411. Here, in the following description, the
surface on the acoustic lens 44 side of the substrate body 411 is referred to as the front surface
411A, and the surface facing the sealing plate 42 is referred to as the back surface 411B.
Further, the surface (corresponding to one surface) of the vibrating film 412 opposite to the
sealing plate 42 is referred to as an opening surface 412A, and the surface on the sealing plate
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42 side is referred to as an operation surface 412B.
[0028]
As shown in FIG. 4, the substrate main body 411 is a substrate supporting the vibrating film 412,
and is made of, for example, a semiconductor substrate of Si or the like. The vibrating film 412 is
made of, for example, SiO 2 or a laminate of SiO 2 and ZrO 2, and is provided on the back surface
411 B of the substrate body 411. The thickness dimension of the vibration film 412 is
sufficiently smaller than that of the substrate body 411.
[0029]
As shown in FIG. 3, in the central array region Ar1 of the element substrate 41, an ultrasonic
transducer array 46 configured to be an array of ultrasonic transducers 45 for transmitting and
receiving ultrasonic waves is provided. Although the number of ultrasonic transducers 45 is
reduced in FIG. 3 for convenience of explanation, more ultrasonic transducers 45 are actually
arranged. The ultrasonic transducer array 46 receives a transmission array 461 having a first
ultrasonic transducer 451 transmitting ultrasonic waves of a predetermined frequency
(hereinafter also referred to as a fundamental wave), and receives a second harmonic of the
fundamental wave. And a receiver array 462 having a second ultrasound transducer 452.
[0030]
(Structure of Transmission Array) The transmission array 461 is provided in the transmission
area (first area) Ar11 of the array area Ar1. The transmission array 461 is configured by
arranging a plurality of first ultrasonic transducers 451 of the ultrasonic transducers 45 that
transmit a fundamental wave in an array. The transmission array 461 is constituted by a plurality
of first ultrasonic transducers 451 arranged along the X direction (slice direction), and has a
plurality of transmission trains 451A functioning as one transmission channel. The plurality of
transmission strings 451A are arranged in the Y direction (scanning direction).
[0031]
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The first ultrasonic transducer 451 is a vibration area of a vibrating film 412 described later, and
is provided with a first flexible portion 412C corresponding to the first vibrating film, and a first
piezoelectric element 413 provided in the first flexible portion 412C. And is comprised. The first
ultrasonic transducer 451 is configured to be able to transmit an ultrasonic wave of a frequency
(fundamental wave) according to the dimensions of the first flexible portion 412C in the X and Y
directions.
[0032]
The substrate main body 411 is provided with a first opening 411C corresponding to each first
ultrasonic transducer 451. The first opening 411C is closed by the vibrating membrane 412 on
the back surface 411B side. That is, the vibrating membrane 412 has a first flexible portion 412C
that closes the first opening 411C on the back surface 411B side. The first flexible portion 412C
is a vibration area of the vibrating membrane 412, and the outer edge is defined by the first
opening 411C. As described above, the first ultrasonic transducer 451 can transmit the
fundamental wave of the frequency according to the outer dimension of the first flexible portion
412C. That is, the dimensions in the X direction and the Y direction of the first opening 411C are
set to values according to the frequency of the fundamental wave.
[0033]
A first piezoelectric element 413, which is a laminate of the first lower electrode 414, the first
piezoelectric film 415, and the upper electrode 416, is provided on the working surface 412B of
the first flexible portion 412C. The first lower electrode 414 is formed in a straight line along the
X direction across the plurality of first ultrasonic transducers 451 constituting the transmission
array 451A of 1CH. One end (−X side end) of the first lower electrode 414 is located in the
terminal area Ar2 of the outer peripheral portion of the element substrate 41, and the first signal
terminal 414P electrically connected to the circuit board 23 is provided. .
[0034]
The upper electrode 416 is formed linearly along the Y direction, and connects a plurality of
transmission columns 451A aligned in the Y direction, and connects a plurality of reception
columns 452A described later. The ± Y-side end of the upper electrode 416 is connected to the
common electrode line 416A. The common electrode line 416A connects the ends on the ± Y
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14
side of each of the plurality of upper electrodes 416 arranged along the X direction. Both end
portions (± X side end portions) of the common electrode line 416A are located in the terminal
area Ar2, and a common terminal 416P electrically connected to the circuit board 23 is provided.
The common terminal 416P is connected to a reference potential circuit (not shown) of the
circuit board 23, and is set to the reference potential. In the first ultrasonic transducer 451, when
a pulse wave voltage of a predetermined frequency is applied between the first lower electrode
414 and the upper electrode 416, the first flexible portion 412C in the opening area of the first
opening 411C It vibrates and an ultrasonic wave (fundamental wave) is transmitted from the side
of the opening surface 412A to the + Z side.
[0035]
(Structure of Reception Array) The reception array 462 is provided in a reception area (second
area) Ar12 located on the + X side of the transmission area Ar11 in the array area Ar1. The
receiving array 462 is the same as the transmitting array 461 except that the receiving array
462 has a second ultrasonic transducer 452 for receiving the second harmonic of the ultrasonic
transducers 45 instead of the first ultrasonic transducer 451. Configured That is, in the reception
array 462, the plurality of second ultrasonic transducers 452 arranged along the X direction
constitute a reception row 452A functioning as one reception channel, and the plurality of
reception rows 452A are arranged in the Y direction. Be done.
[0036]
The second ultrasonic transducer 452 is a vibration area of a diaphragm 412 described later, and
a second flexible element 412D corresponding to the second diaphragm and a second
piezoelectric element 417 provided in the second flexible section 412D. And is comprised. The
second ultrasonic transducer 452 can receive an ultrasonic wave having a frequency according
to the dimensions of the second flexible portion 412D in the X and Y directions, and in the
present embodiment, the second harmonic wave to the fundamental wave Is configured to be
receivable.
[0037]
The second flexible portion 412D closes the second opening 411D provided in the substrate
main portion 411 in the vibrating film 412 on the back surface 411B side to form a vibration
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15
region. The second openings 411D are provided at positions corresponding to the second
ultrasonic transducers 452 in plan view. The second opening 411D defines the outer edge of the
second flexible portion 412D. That is, the dimensions in the X direction and the Y direction of the
second opening 411D are set to values according to the frequency of the second harmonic. In
this embodiment, for example, the dimension in the Y direction of the second opening 411D is
substantially the same as that of the first opening 411C, and the dimension in the X direction is
approximately one half of that of the first opening 411C. doing.
[0038]
The second piezoelectric element 417 is provided on the operation surface 412B of the second
flexible portion 412D, and is a laminate of the second lower electrode 418, the second
piezoelectric film 419, and the upper electrode 416. The second lower electrode 418 is formed in
a straight line along the X direction across the plurality of second ultrasonic transducers 452
constituting the 1CH reception row 452A. A second signal terminal 418P electrically connected
to the circuit board 23 is provided at one end (+ X side end) of the second lower electrode 418.
[0039]
In the second ultrasonic transducer 452, when the second flexible portion 412D is vibrated by
the ultrasonic wave (second harmonic) reflected from the object and incident on the opening
surface 412A, the upper and lower sides of the second piezoelectric film 419 Causes a potential
difference. Therefore, by detecting the potential difference generated between the second lower
electrode 418 and the upper electrode 416, ultrasonic waves are detected, that is, received.
[0040]
(Configuration of Sealing Plate) The sealing plate 42 is formed to have, for example, the same
shape as the element substrate 41 when viewed in the thickness direction, and is formed of a
semiconductor substrate such as Si or an insulator substrate. In addition, since the material and
thickness of the sealing plate 42 affect the frequency characteristics of the ultrasonic transducer
45, it is preferable to set based on the central frequency of the ultrasonic wave transmitted and
received by the ultrasonic transducer 45.
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[0041]
In the sealing plate 42, a recessed groove 421 is formed in a region facing the array region Ar1
of the element substrate 41. That is, the sealing plate 42 has a plurality of recessed grooves 421
corresponding to the openings 411C and 411D. Thereby, the gap 421A is provided between the
element substrate 41 and the sealing plate 42, and the vibration of the flexible portions 412C
and 412D is not inhibited. Also, the back waves from one ultrasonic transducer 45 can suppress
the inconvenience (cross talk) of being incident on the other adjacent ultrasonic transducers 45.
[0042]
The groove depth of each concave groove 421 may be set to be an odd multiple of 1⁄4 of the
wavelength of the fundamental wave in the transmission region Ar11, and in the reception
region Ar12, the wavelength of the second harmonic wave It may be set to be an odd multiple of
1⁄4 of. Here, when the vibrating film 412 vibrates, ultrasonic waves are emitted as back waves to
the back surface 411 B side as well as the opening surface 412 A side. The back wave is reflected
by the sealing plate 42 and emitted again to the vibrating film 412 through the gap 421A. At this
time, by setting the groove depth as described above, it is possible to shift the phase of the
reflected back wave and the ultrasonic wave emitted from the vibrating film 412 toward the
opening surface 412A, thereby attenuating the ultrasonic wave. Can. That is, in consideration of
the wavelength of the ultrasonic wave emitted from the ultrasonic transducer 45, the thickness
dimension of each part of the element substrate 41 and the sealing plate 42 is set.
[0043]
Further, the sealing plate 42 is provided with a connection portion for connecting each of the
terminals 414 P, 416 P, 418 P to the circuit board 23 at a position facing the terminal area Ar 2
of the element substrate 41. As the connection portion, for example, an FPC (Flexible Printed
Circuits), a cable wire, a wire, etc. that connects the terminals 414P, 416P, 418P and the circuit
board 23 through the openings provided in the element substrate 41 and the corresponding
openings. And a wiring member.
[0044]
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17
(Configuration of Acoustic Lens) The acoustic lens 44 is provided on the acoustic layer 43 (+ Z
side) described in detail later. The acoustic lens 44 is exposed to the outside from the sensor
window 21B of the housing 21 as shown in FIG. Also, the acoustic impedance of the acoustic lens
44 is set to an acoustic impedance (for example, 1.5 MRayls) close to the acoustic impedance of
the living body. The surface on the + Z side of the acoustic lens 44 is a curved surface that curves
to the + Z side as it goes to the central portion (the boundary position between the transmission
area Ar11 and the reception area Ar12) along the X direction. The acoustic lens 44 is brought
into close contact with the surface of the living body, thereby efficiently focusing the ultrasonic
wave transmitted from the transmitting array 461 at a desired position in the living body via the
acoustic layer 43 and reflecting it in the living body. These ultrasonic waves are efficiently
propagated to the receiving array 462.
[0045]
Note that the acoustic lens 44 overlaps the transmission area Ar11 of the surface on the −Z side
in plan view, overlaps the first surface portion 441 facing the transmission array 461, and the
reception area Ar12, and faces the reception array 462 And a two-sided portion 442. The first
surface 441 and the second surface 442 are parallel to the XY plane, and the second surface 442
is located on the −Z side of the first surface 441. As a result, as described later, the acoustic
layer 43 can be thinner in the reception area Ar12 than in the transmission area Ar11.
[0046]
As a material for forming such an acoustic lens 44, for example, a millable silicone rubber can be
exemplified. The millable silicone rubber contains, for example, silicone rubber having a
dimethylpolysiloxane structure containing a vinyl group, silica, and a vulcanizing agent.
Specifically, silica is mixed with silicone rubber as a silica particle having a weight average
particle diameter of 15 μm to 30 μm and a mass ratio of 40% by mass to 50% by mass with
respect to the silicone rubber. As a vulcanizing agent, for example, 2,5-dimethyl-2,5-ditertbutylperoxyhexane can be used.
[0047]
(Configuration of Acoustic Layer) FIG. 5 is a view schematically showing the ultrasonic device 22.
As shown in FIG. In FIG. 5, the configuration of the ultrasonic device 22 is simplified, and the
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cross sections of the vibrating film 412, the acoustic layer 43, and the acoustic lens 44 of the
ultrasonic device 22 are schematically shown. The acoustic layer 43 is provided on the surface
on the + Z side of the element substrate 41 (the front surface 411A of the substrate body 411
and the opening surface 412A of the vibrating film 412), as shown in FIG. The acoustic layer 43,
together with the acoustic lens 44, efficiently propagates the ultrasonic wave transmitted from
the ultrasonic transducer 45 to the living body to be measured, and efficiently reflects the
ultrasonic wave reflected in the living body. Propagating to For this reason, the acoustic layer 43
is set to acoustic impedance (for example, 1.0 MRayls) smaller than an acoustic lens. As a
material which has such an acoustic impedance, silicone resin materials, such as RTV silicone
rubber, can be used, for example.
[0048]
The acoustic layer 43 has a first acoustic layer 431 stacked on the + Z side of the transmission
area Ar11, and a second acoustic layer 432 stacked on the + Z side of the reception area Ar12.
That is, the Z direction is the stacking direction of the acoustic layer 43 with respect to the
ultrasonic transducer array 46. In the present embodiment, the first acoustic layer 431 and the
second acoustic layer 432 are integrally formed of the same material. Therefore, the first
acoustic layer 431 and the second acoustic layer 432 have the same sound velocity and acoustic
impedance as ultrasonic waves. The first acoustic layer 431 and the second acoustic layer 432
are not limited to being integrally formed, and, for example, the boundary position between the
transmission area Ar11 and the reception area Ar12 (a position indicated by an alternate long
and short dash line in FIG. And may be formed separately.
[0049]
The dimension L1 (thickness dimension and corresponding to the first dimension) of the first
acoustic layer 431 in the Z direction is λa / 2 when the wavelength λa of the fundamental wave
(the wavelength in the acoustic layer 43) is used. For example, when the frequency of the
transmission wave is 5 MHz, the dimension L1 of the first acoustic layer 431 is 0.2 mm. Note
that L1 is an interface between the first acoustic layer 431 and the acoustic lens 44 (hereinafter
referred to as “the interface between the opening surface 412A (the interface between the first
acoustic layer 431 and the vibrating film 412 and also referred to as the first interface F1 (see
FIG. 5)). The distance to the second interface F2 (also referred to as FIG. 5).
[0050]
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19
The thickness dimension L2 of the second acoustic layer 432 is λb / 2 when the wavelength λb
of the second harmonic (the wavelength in the acoustic layer 43) is used. Since λb = λa / 2, the
thickness dimension of the second acoustic layer 432 is λa / 4, and L2 = L1 / 2. L2 is the
distance between the interface of the second acoustic layer 432 and the acoustic lens 44
(hereinafter also referred to as the third interface F3 (see FIG. 5)) and the opening surface 412A
(first interface F1).
[0051]
FIG. 6 is a view for explaining the action of the acoustic layer 43. As shown in FIG. In the present
embodiment, by setting the thickness L1 of the first acoustic layer 431 = λa / 2 and setting the
thickness L2 of the second acoustic layer 432 = λa / 4, the measurement accuracy (resolution)
will be described below. Can be improved.
[0052]
Here, a pulse wave voltage is applied to the first ultrasonic transducer 451, and an ultrasonic
wave (a transmission wave U0 as a fundamental wave) is transmitted. At this time, as shown in
the upper part of FIG. 6, a compression wave having a plurality of peaks including reverberation
is transmitted as the transmission wave U0, and so-called tailing occurs. That is, by detecting the
reverberation (tailing) part following the first wave u1 of the transmission wave U0, that is, the
reflected wave by the second wave u2 and the third wave u3, the resolution may be reduced and
the measurement accuracy may be reduced. There is. Also on the receiving side, there is a
possibility that the resolution may be reduced due to tailing. That is, as shown in the lower part
of FIG. 6, the reception wave V0 is also a compressional wave having a plurality of peaks
including reverberation, and includes the second wave v2 and the third wave v3 as a tailing
portion following the first wave v1. . The detection of these tailing portions by the second
ultrasonic transducer 452 may reduce the resolution and the measurement accuracy. Further, in
the present embodiment, in the case where the acoustic impedance is different with the second
interface F2 as the boundary, when multiple reflection of ultrasonic waves occurs between the
first interface F1 and the second interface F2, a plurality of corresponding ultrasonic waves are
generated. Peaks may be detected, which may reduce the measurement accuracy.
[0053]
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20
On the other hand, in the present embodiment, the dimension L1 of the first acoustic layer 431 is
λa / 2. That is, on the transmission side, a part of the transmission wave U0 transmitted from
the first ultrasonic transducer 451 and propagating the first acoustic layer 431 to the + Z side is
reflected by the second interface F2, and an interface reflection wave (hereinafter 1) An interface
reflection wave U1 is generated. The first interface reflected wave U1 propagating through the
first acoustic layer 431 to the −Z side reverses in phase when it is reflected by the first interface
F1 (the opening surface 412A). For this reason, by setting the thickness dimension of the first
acoustic layer 431 to λa / 2, the phase of the first interface reflected wave U1 that propagates
by one wavelength λa and is incident on the second interface F2 again is obtained at the second
interface F2. It can be in reverse phase with the second wave u2 of the transmission wave U0.
Therefore, as shown in the upper diagram of FIG. 6, the tailing portion after the second wave u2
of the transmission wave U0 can be canceled by the first interface reflected wave U1. Therefore,
it is possible to suppress a decrease in measurement accuracy due to tailing of the transmission
wave.
[0054]
Furthermore, in the present embodiment, the thickness dimension L2 of the second acoustic
layer 432 = λb / 2, that is, L2 = L1 / 2. That is, on the reception side, a part of the reception
wave (second harmonic) V0 propagating to the −Z side of the second acoustic layer 432 is
reflected at the first interface F1 and an interface reflection wave (hereinafter, the second
interface reflection) (Referred to as wave V1). At this time, the phase of the ultrasonic wave is
reversed. Therefore, by setting the thickness dimension of the first acoustic layer 431 to λb / 2,
the phase of the second interface reflection wave V1 that propagates by one wavelength λb in
the second acoustic layer 432 and is incident on the second interface F2 again can be obtained.
And the second wave v2 of the second interface F2 can be in reverse phase with the second wave
v2 of the received wave V0. As a result, as shown in the lower part of FIG. 6, the tailing portion
after the second wave v2 of the reception wave V0 can be canceled by the second interface
reflection wave V1. Therefore, it is possible to suppress a decrease in measurement accuracy due
to tailing of the received wave.
[0055]
Here, in the case of the thickness dimension L2 = L1 = λb of the second acoustic layer 432, as
shown in the lower part of FIG. 6, the second interface reflection wave V1 propagates until it is
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21
incident again on the first interface F1. Is two wavelengths. For this reason, the second interface
reflected wave V1 is canceled out with the third wave v3 of the reception wave V0 when reincident on the first interface F1. Thus, the second wave v2 is not canceled and the second wave
v2 is received. Therefore, even if the second wave u2 and subsequent waves that are tailing
portions can be canceled on the transmission side, only the third wave v3 and subsequent waves
on the tailing portion can cancel each other on the reception side, which may lower the
resolution. On the other hand, in the present embodiment, by setting the thickness dimension L2
= L1 / 2 of the second acoustic layer 432, the tailing portion after the second wave v2 is
canceled not only on the transmission side but also on the reception side. It is possible to
preferably suppress the reduction in resolution.
[0056]
[Operation and Effect of First Embodiment] The following operation and effect can be obtained in
the first embodiment configured as described above. The first dimension L1 of the first acoustic
layer 431 is λa / 2. The second dimension L2 of the second acoustic layer 432 is λb / 2. Thus,
when the second ultrasonic transducer 452 receives the second harmonic wave to the ultrasonic
wave (fundamental wave) transmitted from the first ultrasonic transducer 451, the reduction in
resolution can be suppressed. That is, as described above, since the first dimension L1 is λa / 2,
the first interface reflection wave U1 generated at the second interface F2 of the transmission
wave (fundamental wave) U0 is re-transmitted to the second interface F2. At the time of
incidence, the phase is delayed by one wavelength with respect to the transmission wave U0 and
is in reverse phase. Therefore, the first interface reflected wave U1 cancels out the second wave
u2 and subsequent ones of the reverberation portion of the transmission wave U0. On the other
hand, since the second dimension L2 is λb / 2, the second interface reflection wave V1
generated at the first interface F1 of the reception wave (second harmonic) V0 is reflected at the
second interface F2, When re-incident on the first interface F1, the phase is delayed by one
wavelength with respect to the reception wave V0, and is in reverse phase. Therefore, the second
interface reflected wave V1 cancels out the second wave v2 and subsequent ones of the
reverberation portion of the received wave V0. From the above, it is possible to suppress the
reduction in resolution due to the detection of the reverberation component of the ultrasonic
wave on both the transmission side and the reception side, that is, the reduction in resolution due
to the influence of tailing, and the reduction in measurement accuracy.
[0057]
Further, in the present embodiment, the first surface portion 441 of the acoustic lens 44 and the
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22
second surface portion 442 are different in position in the Z direction. In such a configuration,
when the acoustic layer 43 and the acoustic lens 44 are provided on the element substrate 41,
the acoustic lens 44 is disposed at an appropriate position (for example, a distance in the Z
direction) with respect to the element substrate 41. The thickness dimension of the layer 43 can
be set. That is, by appropriately setting the distance in the Z direction of the first surface portion
441 and the second surface portion 442 according to the arrangement position of the acoustic
lens 44 with respect to the element substrate 41, the first acoustic layer 431 and the first
acoustic layer 431 having an appropriate thickness dimension The two acoustic layers 432 can
be easily formed.
[0058]
Second Embodiment Hereinafter, a second embodiment will be described. In the first
embodiment, the acoustic layer 43 includes a first acoustic layer 431 and a second acoustic layer
432 having a thickness dimension that is half that of the first acoustic layer 431. On the other
hand, the second embodiment is mainly different from the first embodiment in that the second
acoustic layer is composed of a plurality of layers and has the same thickness as the first acoustic
layer 431. In the following description, the same components as those in the first embodiment
are denoted by the same reference numerals, and the description thereof is omitted or simplified.
[0059]
FIG. 7 is a view schematically showing an ultrasonic device 22A of the second embodiment. As
shown in FIG. 7, the acoustic lens 44 </ b> A differs from the acoustic lens 44 of the first
embodiment in that the array facing surface 443 which is the surface on the −Z side is planar.
The acoustic layer 43A has a first acoustic layer 431 and a second acoustic layer 47. The second
acoustic layer 47 has the same thickness as the first acoustic layer 431, that is, L1 (= λa / 2),
and the first layer 471 and a second layer 472 stacked on the + Z side of the first layer 471. And.
The first layer 471 and the second layer 472 are formed using, for example, a silicone resin
material such as RTV silicone rubber, and the sound velocity of the propagating ultrasonic wave
is substantially the same. In the present embodiment, the second layer 472 is integrally formed
with the first acoustic layer 431.
[0060]
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23
The first layer 471 is filled in the second opening 411D and provided on the second flexible
portion 412D. The acoustic impedance of the first layer 471 is larger than the acoustic
impedance of the second layer 472. For example, the acoustic impedance of the first layer 471 is
1.5 MRayls, and the acoustic impedance of the second layer 472 is 1.0 MRayls. Such a first layer
471 can be formed, for example, by dispersing a filler in a silicone resin material forming the
second layer 472, whereby the acoustic impedance can be made larger than that of the second
layer 472.
[0061]
The thickness dimension of the first layer 471 and the second layer 472 is an odd multiple of λb
/ 4. In addition, the thickness dimension of at least one of the first layer 471 and the second
layer 472 is λb / 2 or less. In the present embodiment, the thickness dimension L3 of the first
layer 471 is λb / 4, and the thickness dimension L4 of the second layer 472 is λb · (3/4). In
other words, the thickness dimension L3 of the first layer 471 is λa / 8, and the thickness
dimension L4 of the second layer 472 is λa (3/8). By setting the thickness dimensions of the
first layer 471 and the second layer 472 to the above values, it is possible to suppress the
decrease in measurement accuracy due to the above-described tailing, and to set the thickness
dimensions of the second acoustic layer 47 It can be the same.
[0062]
FIG. 8 is a diagram for explaining the action of the acoustic layer 43A. In FIG. 8, the configuration
of the ultrasonic device 22A is simplified, and cross sections of the vibrating film 412, the
acoustic layer 43A, and the acoustic lens 44A of the ultrasonic device 22 are schematically
shown. In FIG. 8, the interface between the second acoustic layer 47 and the vibrating film 412 is
a first interface F1, the interface between the second acoustic layer 47 and the acoustic lens 44A
is a third interface F3, and a first layer 471 and a second layer The interface with 472 is referred
to as a fourth interface F4. In the present embodiment, when the ultrasonic wave propagating
through the first layer 471 is reflected by the first interface F1 and the fourth interface F4, the
phase of the ultrasonic wave is reversed.
[0063]
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24
As shown in FIG. 8, a part of the received wave V0 incident on the first interface F1 is reflected
by the first interface F1 to generate a second interface reflected wave V1. The phase of the
received wave is reversed at the time of reflection at the first interface F1. A part of the second
interface reflected wave V1 is reflected by the fourth interface F4 and enters the first interface
F1 again. The phase is also reversed when the light is reflected at the fourth interface F4.
Therefore, by setting the thickness dimension of the first layer 471 to λb / 4, the phase of the
second interface reflected wave V1 propagating through the first layer 471 by a half wavelength
(λb / 2) and reincident on the first interface F1. Can be made opposite in phase to the first wave
v1 of the received wave V0 at the first interface F1. As a result, at least a part of the second
interface reflected wave V1 is canceled with a part of the first wave v1 of the reception wave V0
and a tailing portion after the second wave v2. Therefore, it is possible to suppress a decrease in
measurement accuracy due to tailing of the received wave.
[0064]
A part of the second interface reflection wave V1 generated at the first interface F1 is reflected
by the third interface F3 and is incident on the first interface F1 again. Since the thickness
dimension of the second acoustic layer 47 is an integral multiple of λb / 2, the phase of the
second interface reflected wave V1 can be made opposite to the phase of the received wave V0,
and the second interface reflected wave V1 is generated by the received wave V0. Can be offset.
In addition, a part of the reception wave V0 is reflected by the fourth interface F4 to generate a
third interface reflected wave V2. The third interface reflection wave V2 is reflected by the third
interface F3 and enters the fourth interface F4 again. By setting the thickness dimension of the
second layer 472 to an odd multiple of λb / 4, the phase of the third interface reflected wave V2
can be made opposite to the phase of the received wave V0, and the third interface reflected
wave V2 is generated by the received wave V0. It can be offset. Therefore, it is possible to
suppress the decrease in measurement accuracy due to the reception of the interface reflected
wave.
[0065]
[Operation and Effect of Second Embodiment] In the second embodiment configured as described
above, the following operation and effect can be obtained. The first dimension L1 of the first
acoustic layer 431 is λ / 2. In addition, the second acoustic layer 47 has a first layer 471 and a
second layer 472. The third dimension L3 of the first layer 471 is λb / 4 (= λa / 8) and is equal
to or less than λb / 2. In addition, the thickness dimension L4 of the second layer 472 is λb ·
(3/4) = λa (3/8). Thereby, as in the first embodiment, the resolution can be improved when the
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second ultrasonic transducer 452 receives the second harmonic with respect to the transmission
wave (fundamental wave).
[0066]
That is, on the transmission side, as in the first embodiment, the second and subsequent waves in
the reverberation portion of the transmission wave U0 are canceled by the first interface
reflected wave U1. On the other hand, on the reception side, the second interface reflection wave
V1 reflected by the first interface F1 of the reception wave V0 which is the second harmonic is
reflected by the third interface F3 and the fourth interface F4, and When entering the first
interface F1 again, the phase is opposite to that of the received wave V0 and is canceled. Further,
of the reception wave V0, the third interface reflection wave V2 reflected by the fourth interface
F4 is reflected by the third interface F3 and thereafter enters the fourth interface F4 again. It
becomes an antiphase and is canceled. Here, the dimension L3 of the first layer 471 is λb / 2 or
less. Therefore, the second interface reflected wave V1 reflected between the first interface F1
and the fourth interface F4 and propagating in the first layer 471 can cancel at least the second
wave v2 and subsequent of the reverberation portion of the reception wave V0. From the above,
similarly to the transmitting side, a decrease in resolution due to the detection of the second
wave or later of the reverberation component on the receiving side, that is, the influence of
tailing can be suppressed, and a decrease in measurement accuracy can be suppressed.
[0067]
Further, the thickness dimensions of the first acoustic layer 431 and the second acoustic layer 47
are the same. Thus, the interface between the acoustic lens 431 and the acoustic layers 431 and
47 of the acoustic lens 44A provided across the first acoustic layer 431 and the second acoustic
layer 47 can be made flat, and the configuration of the acoustic lens 44A can be simplified.
Further, by setting the dimension L3 of the first layer 471 to λb / 4 and the dimension L4 of the
second layer 472 to λb · (3/4), the first acoustic layer 431 is suppressed while the influence of
the above-mentioned tailing is suppressed. And the size of the second acoustic layer 47 can be
the same.
[0068]
Further, the depth dimension (dimension in the Z direction) of the second opening 411D of the
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substrate main body 411 is taken as the thickness dimension L3 of the first layer 471, and the
first layer 471 is formed in the second opening 411D. Thereafter, by forming the first acoustic
layer 431 and the second layer 472 simultaneously and arranging the acoustic lens 44, the
ultrasonic device 22A can be formed. Thereby, it is easy to make the thickness of the first layer
471 an appropriate dimension. The first acoustic layer 431 and the second layer 472 can be
formed at the same time, and the manufacturing process can be simplified as compared to
separate manufacturing.
[0069]
Also, by making the thickness dimension of the first layer 471 smaller than that of the second
layer 472, it is easy to increase the reception sensitivity. That is, the first layer 471 is a layer
having a larger acoustic impedance than the second layer 472 layer. Such a first layer 471 can
be easily formed by diffusing a filler using the same material as the forming material of the
second layer 472 as a base material as described above. Therefore, by making the thickness of
the second layer 472 having a smaller attenuation coefficient than that of the first layer 471
larger than that of the first layer 471, the reception sensitivity can be increased. In addition, the
acoustic layer 43A including the first layer 471 and the second layer 472 can be easily formed as
described above. From the above, it is easy to increase the reception sensitivity.
[0070]
[Modifications] The present invention is not limited to the above-described embodiments, and
modifications, improvements, and configurations obtained by appropriately combining the
embodiments can be made as long as the objects of the present invention can be achieved. It is
included in the invention.
[0071]
Modified Example 1 In the first embodiment, the first dimension L1 of the first acoustic layer
431 is λa / 2, and the second dimension L2 of the second acoustic layer 432 is λb / 2.
However, the present invention is not limited to this.
For example, the first dimension L1 may be an integer n times λa / 2 (see the following formula
(1)). In addition, the second dimension L2 of the second acoustic layer 432 may be an integer n
times λb / 2 (see the following formula (2)). Even in such a configuration, when the wavelengths
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of the ultrasonic waves are different between the transmission wave and the reception wave, it is
possible to suppress a decrease in measurement accuracy due to the influence of the tailing
being different between the transmission side and the reception side.
[0072]
[Equation 1] L1 = (λa / 2) · n (1) L2 = (λb / 2) · n (2)
[0073]
That is, as described above, the first interface reflection wave U1 generated at the second
interface F2 of the transmission wave U0 propagating through the first acoustic layer 431 is
reflected by the first interface F1, and then again the second interface Incident on F2.
At this time, since the first dimension L1 is (λa / 2) · n, the propagation distance of the first
interface reflected wave U1 is λa · n in the round trip of the first acoustic layer 431. Therefore,
at the second interface F2, the phase of the first interface reflected wave U1 is delayed by 2nπ
with respect to the transmission wave U0 and is in reverse phase. Therefore, the (n + 1) th and
subsequent waves of the reverberation portion of the transmission wave U0 are canceled by the
first reflected wave.
[0074]
On the other hand, the second interface reflection wave V1 generated at the first interface F1 of
the reception wave V0 which is a reflection wave from the measuring object is reflected by the
third interface F3 and then enters the first interface F1 again. At this time, since the second
dimension L2 is (λb / 2) · n, similarly, the phase of the second interface reflected wave V1 at the
first interface F1 is delayed by 2nπ with respect to the reception wave V0, and , Out of phase.
Therefore, the (n + 1) th and subsequent waves of the reverberation portion of the received wave
V0 are canceled out.
[0075]
As described above, by setting the thicknesses of the first acoustic layer 431 and the second
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acoustic layer 432 according to the corresponding wavelengths, it is possible to detect the n +
1th and subsequent waves on both the transmitting side and the receiving side. It can be
suppressed. Therefore, even when the transmission wave and the reception wave are different as
in the case of receiving high-order harmonics to the transmission wave, it is possible to suppress
the decrease in measurement accuracy due to the influence of the tailing on the transmission
side and the reception side being different. .
[0076]
Modification Example 2 In the second embodiment, the first dimension L1 of the first acoustic
layer 431 is λa / 2, and the third dimension L3 of the first layer 471 is λb / 4, that is, λb / 2
or less. The fourth dimension L4 of the layer 472 is λa · (3/8). However, it is not limited to this.
For example, the first dimension L1 is an integer n times λa / 2 (see the above equation (1)), the
dimensions of the first layer 471 and the second layer 472 are odd multiples of λb / 4, and the
first layer is The dimension of at least one of 471 and the second layer 472 may be equal to or
less than an integer n times λb / 2. Even in such a configuration, when the wavelengths of the
ultrasonic waves are different between the transmission wave and the reception wave, it is
possible to suppress a decrease in measurement accuracy due to the influence of the tailing
being different between the transmission side and the reception side.
[0077]
That is, by setting the first dimension L1 of the first acoustic layer 431 to an integral multiple
(for example, n times) of λa / 2, the n + 1th and subsequent waves in the reverberation portion
of the transmission wave U0 are the first interface reflected wave U1. Offset by On the other
hand, when the dimensions of the first layer 471 and the second layer 472 are an odd multiple of
λb / 4, the second interface reflected wave V1 reenters the first interface F1 as in the second
embodiment. , The phase is opposite to that of the received wave V0 and is canceled. When the
third interface reflected wave V2 reenters the fourth interface F4, the third interface reflected
wave V2 has an opposite phase to the received wave V0 and is canceled.
[0078]
Here, the dimension of at least one of the first layer 471 and the second layer 472 is equal to or
less than an integer n times λb / 2. Therefore, at least one of the second interface reflected wave
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V1 and the third interface reflected wave V2 has a propagation distance of λb · n or less, and a
delay amount of 2nπ or less and an opposite phase with respect to the received wave. For this
reason, at least the (n + 1) th and subsequent waves of the reverberation portion of the reception
wave V0 are canceled by at least one of the second interface reflection wave V1 and the third
interface reflection wave V2.
[0079]
From the above, it can be suppressed that the (n + 1) th and subsequent waves are detected on
both the transmitting side and the receiving side. Therefore, even when the transmission wave
and the reception wave are different as in the case of receiving high-order harmonics to the
transmission wave, it is possible to suppress the decrease in measurement accuracy due to the
influence of the tailing on the transmission side and the reception side being different. .
[0080]
(Other Modifications) In the first embodiment, the thickness dimension of the second acoustic
layer 432 is larger than the depth dimension of the second opening 411D. However, the present
invention is not limited thereto. The depth dimension of 411 D may be the thickness dimension
of the second acoustic layer 432. Thereby, it is easy to adjust the thickness of the second
acoustic layer 432. Similarly, the depth dimension of the first opening 411C may be the
thickness dimension of the first acoustic layer 431.
[0081]
In the second embodiment, the dimension of the first layer 471 is exemplified to be smaller than
that of the second layer 472. However, without limitation thereto, the dimension of the first layer
471 may be larger than that of the second layer 472. For example, the dimension of the first
layer 471 may be λb · (3/4), and the dimension of the second layer 472 may be λb / 4. Such a
configuration can also suppress the influence of tailing as in the second embodiment.
[0082]
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In each of the above-described embodiments, the acoustic layer is disposed to cover the side of
the opening surface 412A of the diaphragm 412, that is, the substrate body 411. However, the
present invention is not limited to this, and the acoustic layer may be provided on the opposite
side of the substrate body 411 so as to cover the actuating surface 412 B of the vibrating
membrane 412. FIG. 9 is a cross-sectional view schematically showing an ultrasonic device 22B
according to a modification. As shown in FIG. 9, the ultrasonic device 22B includes an element
substrate 41, a sealing plate 42B disposed on the -Z side of the element substrate 41, an acoustic
layer 43 disposed on the + Z side of the element substrate 41, and acoustics. And a lens 44. In
the ultrasonic device 22B, the vibrating film 412 is provided on the + Z side of the substrate body
411. That is, the surface on the −Z side of the vibrating membrane 412 is the opening surface
412A, and the surface on the + Z side is the actuating surface 412B. The first piezoelectric
element 413 and the second piezoelectric element 417 are provided on the operation surface
412B. In addition, the sealing plate 42B is formed in a flat plate shape, and provided on the −Z
side of the element substrate 41 so as to face the substrate main body 411. The configuration
other than the above is basically the same as that of the first embodiment.
[0083]
Although said each embodiment demonstrated the case where the sound speed of an ultrasonic
wave was the same in a 1st acoustic layer and a 2nd acoustic layer, it is not limited to this. For
example, the speed of sound may be different between the first acoustic layer and the second
acoustic layer. Moreover, although the said each embodiment illustrated the structure which
receives the 2nd harmonic with respect to a transmission wave, it is not limited to this. For
example, the second ultrasonic transducer may be capable of receiving third or higher
harmonics. Even in such a case, by setting the thickness dimension of each layer of the acoustic
layer according to the corresponding wavelength, it is possible to suppress the decrease in
measurement accuracy due to the influence of the tailing on the transmission side and the
reception side being different.
[0084]
In each of the above embodiments, the ultrasonic transducer array 46 including the first
ultrasonic transducer 451 for transmission and the second ultrasonic transducer 452 for
reception is illustrated, but it is not limited thereto. That is, both of the first ultrasonic transducer
451 and the second ultrasonic transducer 452 may be configured to be able to both transmit and
receive ultrasonic waves. That is, ultrasonic waves may be transmitted and received by the first
ultrasonic transducer 451, and ultrasonic waves may be transmitted and received by the second
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31
ultrasonic transducer 452. As described above, even if ultrasonic transducer arrays that transmit
and receive ultrasonic waves of different frequencies (wavelengths) are formed on the same
substrate, it is possible to suppress the reduction in resolution of the ultrasonic transducer
arrays.
[0085]
In each of the above embodiments, the transmitting array 461 and the receiving array 462 are
respectively configured as a one-dimensional array in which the transmitting channel or the
receiving channel is arranged in one direction, but the present invention is not limited thereto.
For example, each channel which can be driven individually may be configured as a twodimensional array arranged in a matrix. In this case, instead of the acoustic lens, a protective film
or the like having a larger acoustic impedance than the acoustic layer is disposed on the acoustic
layer. Even with such a configuration, it is possible to suppress the decrease in measurement
accuracy due to the influence of the tailing being different on the transmission side and the
reception side.
[0086]
Although the above-mentioned each embodiment illustrated the composition provided with a
diaphragm and the piezoelectric element formed on the diaphragm as an ultrasonic transducer
45, it is not limited to this. For example, as the ultrasonic transducer 45, a configuration
including a flexible film, a first electrode provided on the flexible film, and a second electrode
provided at a position facing the first electrode in the sealing plate It may be adopted. The first
electrode and the second electrode constitute an electrostatic actuator as a vibrator. In such a
configuration, ultrasonic waves can be transmitted by driving the electrostatic actuator and
ultrasonic waves can be detected by detecting the capacitance between the electrodes.
[0087]
In each of the above embodiments, as the electronic device, the ultrasonic device in which an
organ in a living body is to be measured is exemplified, but the present invention is not limited to
this. For example, the configurations of the above-described embodiment and each modification
can be applied to a measuring machine that performs detection of defects of the structures and
inspection of deterioration with various structures as targets of measurement. In addition, for
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example, the same applies to a measuring device that detects a defect of a measurement target
with a semiconductor package, a wafer, or the like as the measurement target.
[0088]
In addition, the specific structure in the practice of the present invention may be configured by
appropriately combining the above-described embodiments and modifications within the range in
which the object of the present invention can be achieved. You may
[0089]
DESCRIPTION OF SYMBOLS 1 ... Ultrasonic measuring device, 2 ... Ultrasonic probe, 10 ... Control
apparatus, 21 ... Housing | casing 22, 22A, 22B ... Ultrasonic device, 41 ... Element board, 42 ...
Sealing plate, 43, 43A ... Acoustic layer , 44, 44A: acoustic lens, 45: ultrasonic transducer, 46:
ultrasonic transducer array, 411: substrate body, 411A: front surface, 411B: back surface, 411C,
first opening, 411D, second opening , 412: diaphragm, 412A: opening surface, 412B: working
surface, 412C: first flexible part, 412D: second flexible part, 413: first piezoelectric element, 414:
first lower electrode, 415: first Piezoelectric film 416 upper electrode 417 second piezoelectric
element 418 second lower electrode 419 second piezoelectric film 421 concave groove 421A
gap 431 first acoustic layer 432 second acoustic layer, 41 first surface portion 442 second
surface portion 451 first ultrasonic transducer 452 second ultrasonic transducer 461
transmission array 462 reception array 471 first layer 472 second Layer, Ar1 ... array area, Ar11
... transmission area, Ar12 ... reception area.
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