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DESCRIPTION JP2016161682

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DESCRIPTION JP2016161682
Abstract: The present invention provides an acoustic Fresnel lens capable of forming a layer
capable of effectively preventing sound wave leakage and efficiently focusing the sound wave,
and a method of manufacturing the same. An acoustic Fresnel lens 1 has a first lens 10 in which
a plurality of prisms having a lens surface 5A and a non-lens surface 5B are arrayed in a first
laminated surface 12, and a lens surface 6A and a non-lens surface 6B. And a second lens 20 in
which a plurality of prisms are arranged on the second laminated surface 22. The incident
surface 11 on which the ultrasonic wave is incident is provided on the opposite surface of the
first laminated surface 12. An emission surface 21 from which the ultrasonic wave is emitted is
provided on the opposite surface of the second laminated surface 22. The plurality of prisms of
the second lens 20 are alternately disposed between the plurality of prisms of the first lens 10,
and the first lens 10 and the second lens 20 are stacked. An adhesive layer 80 is provided
between the lens surface 5A and the lens surface 6A, and an air layer is provided between the
non-lens surface 5B and the non-lens surface 6B. [Selected figure] Figure 10
Acoustic Fresnel lens and method of manufacturing the same
[0001]
The present invention relates to an acoustic Fresnel lens having a layer for preventing sound
wave leakage and a method of manufacturing the same.
[0002]
BACKGROUND Conventionally, an optical device is known that includes a semiconductor element,
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a light receiving unit provided on the main surface of the semiconductor element, and a light
transmitting plate (optical lens) stacked on the main surface of the semiconductor element.
Patent Document 1 includes, on one surface, an uneven portion including a first side surface
perpendicular to the main surface of the semiconductor element and a second side surface acute
to the main surface. Disclosed is a Fresnel lens having an antireflective film formed on a first side.
[0003]
Unexamined-Japanese-Patent No. 2010-245922
[0004]
The Fresnel lens disclosed in Patent Document 1 collects light by converging light.
On the other hand, it is known that an acoustic Fresnel lens including an uneven portion on one
surface is also used as an acoustic lens that converges a sound wave. In the film forming step of
forming the antireflective film only on the first side, precise processing may be required, and it
may be difficult to form an effective antireflective film particularly in a small acoustic lens. In
addition, there are acoustic Fresnel lenses for focusing sound waves that are made of synthetic
resin. In the uneven portion of such an acoustic Fresnel lens, when the antireflective film is
provided on the first side, the acoustic impedance of the medium of the acoustic Fresnel lens
tends to exhibit a value relatively close to that of the antireflective film. In this case, the sound
waves easily leak from the first side surface. There is a problem that the leaked sound wave may
be emitted and may block the focusing of the sound wave emitted from the second side.
[0005]
An object of the present invention is to provide an acoustic Fresnel lens capable of forming a
layer capable of effectively preventing the leakage of sound waves and capable of efficiently
focusing sound waves, and a method of manufacturing the same.
[0006]
An acoustic Fresnel lens according to a first aspect of the present invention is an acoustic Fresnel
lens for focusing and emitting an incident sound wave, which comprises: a plurality of prisms
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having a lens surface and a non-lens surface; A second Fresnel lens laminated to the first Fresnel
lens, the first Fresnel lens being an incident surface on which a sound wave is incident, and a
surface opposite to the incident surface, the second Fresnel lens being The second Fresnel lens is
a surface opposite to the second laminated surface, and the second laminated surface laminated
on the first laminated surface of the first Fresnel lens. A first lens surface and a plurality of first
non-lens surfaces having a first lens surface and a first non-lens surface facing in a direction
different from the direction in which the first lens surface faces. Provided with a prism, The
laminated surface includes a plurality of second prisms having a second lens surface and a
second non-lens surface facing in a direction different from the direction in which the second
lens surface faces, and between each of the plurality of first prisms An adhesive agent for
alternately arranging the plurality of second prisms and bonding the first lens surface to the
second lens surface between the first lens surface and the second lens surface; The adhesive
layer is provided, and an air layer separated by a predetermined gap is provided between the first
non-lens surface and the second non-lens surface.
[0007]
According to the acoustic Fresnel lens according to the first aspect of the present invention, the
sound wave incident from the entrance surface of the first Fresnel lens is emitted from the exit
surface of the second Fresnel lens.
The first Fresnel lens and the second Fresnel lens are laminated on the first laminated surface
and the second laminated surface via the adhesive layer.
The adhesive layer can transmit the sound wave emitted from the first lens surface of the first
prism to the second lens surface of the second prism. On the other hand, since the acoustic
impedance in the air layer is much smaller than that in the first Fresnel lens and the second
Fresnel lens which are lens bodies, the sound wave emitted from the first non-lens surface is
attenuated in the air layer, It is hard to be incident from the second non-lens surface. Thus, the
acoustic Fresnel lens according to the first aspect of the present invention can form a layer
capable of effectively preventing the leak of the sound wave, and can efficiently focus the sound
wave.
[0008]
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The first Fresnel lens and the second Fresnel lens may be made of materials having different
acoustic impedances. At the interface of media with different acoustic impedances, the sound
waves are refracted. Since each of the first Fresnel lens and the second Fresnel lens is made of
materials whose acoustic impedances are different from each other, the acoustic Fresnel lens can
exert a lens effect for focusing sound waves.
[0009]
The first Fresnel lens has a larger acoustic impedance than the adhesive layer, and the adhesive
layer is the same as the second Fresnel lens or larger than the second Fresnel lens. You may
have. In this case, since the acoustic Fresnel lens has interfaces of media having different
acoustic impedances, the refractive index of the sound wave can be controlled for each interface.
In addition, since the acoustic impedance gradually decreases from the first Fresnel lens to the
second Fresnel lens, the acoustic Fresnel lens can efficiently focus the sound wave incident from
the incident surface and can emit the sound wave from the output surface.
[0010]
An isolation member for isolating the adhesive layer and the air layer may be provided on at least
one of the first lamination surface and the second lamination surface. In this case, since the
adhesive layer and the air layer are separated by the separating member, for example, the air of
the air layer flows into the adhesive layer, and the transmission of the sound wave from the first
lens surface to the second lens surface is by air. The possibility of being inhibited can be reduced.
Thus, the acoustic Fresnel lens can efficiently transmit sound waves from the first Fresnel lens to
the second Fresnel lens.
[0011]
The separating member may be a projecting portion provided on the first laminated surface and
protruding from the first laminated surface toward the second prism. In this case, the acoustic
Fresnel lens can reliably separate the adhesive layer and the air layer at the projecting portion.
[0012]
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A positioning unit may be provided to position the second laminated surface of the second
Fresnel lens with respect to the first laminated surface of the first Fresnel lens. In this case, the
acoustic Fresnel lens can prevent the first Fresnel lens and the second Fresnel lens from
deviating from the laminated state.
[0013]
The height in the direction in which the first lens surface of the first prism faces may be greater
than the height in the direction in which the second lens surface of the second prism faces. In
this case, the acoustic Fresnel lens makes the first lens surface wider than in the case where the
height in the direction to which the first lens surface of the first prism faces is smaller than the
height in the direction to which the second lens surface of the second prism faces. The sound
waves can be focused efficiently.
[0014]
The thickness of each of the first Fresnel lens and the second Fresnel lens may be one fourth of
the wavelength of the sound wave incident from the incident surface. In this case, the acoustic
Fresnel lens can effectively prevent the reflection of sound waves on the respective surfaces of
the first Fresnel lens and the second Fresnel lens.
[0015]
A method of manufacturing an acoustic Fresnel lens according to a second aspect of the present
invention is an acoustic Fresnel lens for focusing and emitting an incident sound wave, wherein
the acoustic Fresnel lens is a prism having a lens surface and a non-lens surface. A plurality of
first Fresnel lenses arranged in a plurality, and a second Fresnel lens stacked on the first Fresnel
lenses, wherein the first Fresnel lenses have an incident surface on which a sound wave is
incident and a surface opposite to the incident surface A second laminated surface laminated on
the first laminated surface of the first Fresnel lens; and a second laminated surface laminated on
the first laminated surface of the first Fresnel lens; The first laminated surface is a surface
opposite to the second laminated surface, which emits an acoustic wave, and the first laminated
surface is a first lens surface facing the first lens surface and a first non-convex surface facing in
a direction different from the direction in which the first lens surface faces. With lens surface
And the second laminated surface includes a plurality of second prisms having a second lens
surface and a second non-lens surface facing in a direction different from the direction in which
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the second lens surface faces. And applying the adhesive to the first lens surface, and arranging
the second laminated surface of the second Fresnel lens to face the first laminated surface of the
first Fresnel lens. Positioning the first Fresnel lens and the second Fresnel lens to each other such
that each of the plurality of second prisms is alternately disposed between each of the plurality of
first prisms And, in the first and second Fresnel lenses positioned in the positioning step, the first
lens surface to which the adhesive is applied in the coating step. An adhesive layer for bonding
the first lens surface and the second lens surface is formed by bonding the second laminated
surface to which no adhesive is applied, and the first non-lens surface, and And a bonding step of
forming an air layer separating the first non-lens surface and the second non-lens surface with a
predetermined gap between the second non-lens surface and the second non-lens surface.
[0016]
If an acoustic Fresnel lens is produced according to the manufacturing method according to the
second aspect of the present invention, a layer capable of effectively preventing the leak of the
acoustic wave can be formed, and an acoustic Fresnel lens capable of efficiently focusing the
acoustic wave can be obtained.
[0017]
FIG. 2 is a cross-sectional view showing an outline of the ultrasonic transducer 100.
FIG. 1 is a perspective view of an acoustic Fresnel lens 1;
FIG. 2 is a plan view of the first lens 10; It is an II arrow direction sectional view in FIG. FIG. 6 is a
bottom view of a second lens 20. It is the II-II arrow directional cross-sectional view in FIG. 5 is a
flowchart showing a manufacturing process of the acoustic Fresnel lens 1; It is an explanatory
view showing an application process. It is an explanatory view showing a positioning process. It
is an explanatory view showing an adhesion process. It is a sectional view showing an outline of
acoustic Fresnel lens 200 in a modification.
[0018]
Embodiments of the present invention will be described with reference to the drawings. First, the
structure of the ultrasonic transducer 100 will be described with reference to FIG. The ultrasonic
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transducer 100 is an element for refracting and focusing an ultrasonic wave generated by the
piezoelectric element 2 oscillated by the input of an electric signal by the acoustic Fresnel lens 1
and outputting it to the outside. The ultrasonic transducer 100 is used, for example, as a deep
probe (probe) of an ultrasonic diagnostic apparatus. In the present embodiment, the piezoelectric
element 2 generates an ultrasonic wave having a frequency of about 1 MHz.
[0019]
The piezoelectric element 2 is an element whose magnitude changes in a predetermined
direction by the application of a voltage. The shape of the piezoelectric element 2 is a disk shape
in which the direction in which the size changes is the thickness direction. For example, PZT (lead
zirconate titanate) is used for the piezoelectric element 2. The piezoelectric element 2 vibrates by
displacement according to the strength of the input electric signal to generate an ultrasonic
wave. The piezoelectric element 2 is integrally fixed to the acoustic Fresnel lens 1 using, for
example, an epoxy adhesive. The acoustic Fresnel lens 1 includes an incident surface 11 on
which the ultrasonic wave generated by the piezoelectric element 2 is incident. The acoustic
Fresnel lens 1 refracts and focuses the incident ultrasonic wave inside, and emits it from the
emission surface 21 to the outside.
[0020]
The structure of the acoustic Fresnel lens 1 will be described with reference to FIGS. 2 to 6. As
shown in FIG. 2, the acoustic Fresnel lens 1 has a disk shape extending in the vertical direction.
The acoustic Fresnel lens 1 is formed by stacking the first lens 10 and the second lens 20 in the
vertical direction by overlapping the second lens 20 with the first lens 10 from the upper side.
The first lens 10 and the second lens 20 each have a disk shape having a circular shape with the
same diameter in plan view. As will be described later, the first lens 10 and the second lens 20
are both Fresnel lenses provided with a surface having a Fresnel shape. In the acoustic Fresnel
lens 1, the first lens 10 and the second lens 20 are laminated such that the respective surfaces
on the side having the Fresnel shape of the first lens 10 and the second lens 20 are inside. The
lower surface of the first lens 10 is the surface opposite to the surface having the Fresnel shape,
and constitutes the incident surface 11 of the acoustic Fresnel lens 1. The upper surface of the
second lens 20 is the surface opposite to the surface having the Fresnel shape, and constitutes
the emission surface 21 of the acoustic Fresnel lens 1. The entrance surface 11 and the exit
surface 21 are respectively flat surfaces. Since the incident surface 11 is a flat surface, the
acoustic Fresnel lens 1 can fix the piezoelectric element 2 in close contact with the incident
surface 11 and can efficiently cause the ultrasonic wave generated by the piezoelectric element 2
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to enter inside.
[0021]
The structure of the first lens 10 will be described with reference to FIGS. 3 and 4. As shown in
FIGS. 3 and 4, the first lens 10 is a first laminated surface in which a plurality of prisms 5
including a lens surface 5A and a non-lens surface 5B are concentrically arranged around the
optical center C1. It has twelve. The first laminated surface 12 is a surface on which the second
lens 20 is laminated, and is a surface disposed inside the acoustic Fresnel lens 1. In the present
embodiment, the first lens 10 is an acrylic resin, but may be made of other synthetic resin. In this
embodiment, it is made of acrylic resin. The first lens 10 can be obtained by polymerizing a raw
material of an acrylic resin in a mold (not shown).
[0022]
The acoustic impedance of the first lens 10 made of acrylic resin is approximately 3.3 × 10 6
<6> N · s / m 3. Further, the acoustic impedance of the piezoelectric element 2 which is PZT is
approximately 30 × 10 6 <6> N · s / m 3. The acoustic impedance has different values
depending on the density specific to the medium. When sound waves propagate between
different media, the smaller the difference in acoustic impedance between the media, the less the
reflection of the sound waves between the media will occur. The acoustic Fresnel lens 1 is made
of an acrylic resin having a relatively high acoustic impedance in the synthetic resin to make the
acoustic impedance of the piezoelectric element 2 which is a sound source of the ultrasonic
transducer 100 approach the acoustic impedance of the first lens 10. Configured. Therefore,
when the acoustic Fresnel lens 1 causes the ultrasonic wave to be incident from the incident
surface 11, the reflection of the ultrasonic wave can be reduced and the ultrasonic wave
generated by the piezoelectric element 2 can be efficiently made to enter inside.
[0023]
As shown in FIG. 3, the lens surface 5A is formed as an annular surface concentrically arranged
at a predetermined pitch in plan view. The plurality of prisms 5 are arranged with their apexes
directed upward. At a central portion in a plan view of the first laminated surface 12, a central
concave portion 13 which is a portion recessed downward from the apexes of the plurality of
prisms 5 is provided. As shown in FIG. 4, the lens surface 5 </ b> A is inclined obliquely upward
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with respect to the bottom surface of the central recess 13 around the central recess 13. The
angle at which the lens surface 5A is inclined with respect to the bottom surface of the central
recess 13 is an angle approximating a curved surface having a radius of curvature corresponding
to the focal length of the first lens 10. The lens surfaces 5A are arranged concentrically at a
predetermined pitch with such an angle, and the incident surface 11 which is the opposite
surface of the first laminated surface 12 is formed flat. One lens 10 can function as a planoconcave lens. In other words, the lens surface 5A is a surface that acts as a lens in the first lens
10. In the present embodiment, the lens surface 5A is a flat surface, but the lens surface 5A may
have a curved surface.
[0024]
The non-lens surface 5B is a surface connecting the upper end of the lens surface 5A and the
first laminated surface 12. In the present embodiment, the non-lens surface 5B is a plane
extending vertically in the vertical direction, but the non-lens surface 5B may have a curved
surface. Further, the non-lens surface 5B is not limited to a plane extending in the vertical
direction, and may be a slope inclined with respect to the vertical direction. The non-lens surface
5B is a surface having an angle different from that of the lens surface 5A, and in the first lens 10,
it is a surface that does not act directly as a lens.
[0025]
In the first laminated surface 12, receiving portions 30 and 30 which are portions recessed
downward from the apexes of the plurality of prisms 5 are provided at peripheral portions where
the prisms 5 are not disposed. The receiving portions 30, 30 are disposed on an II straight line
parallel to the left-right direction passing through the optical center C1 shown in FIG.
[0026]
The thickness D1 of the first lens 10 shown in FIG. 4 is, for example, 0.825 mm. In media having
different acoustic impedances, the speed of sound in the media is different. The wavelength λ of
the sound wave in the medium is obtained by dividing the speed of sound by the frequency. The
thickness D1 is about one fourth of the wavelength λ of the ultrasonic wave incident on the first
lens 10. Part of the ultrasonic wave incident from the incident surface 11 is reflected on each of
the surface of the incident surface 11 (the surface on the side in contact with the piezoelectric
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element 2) and the back surface of the incident surface 11 (the surface on the inner side of the
first lens 10) . If the thickness D1 of the first lens 10 is a quarter of the wavelength λ of the
incident wave, the reflected wave reflected on the surface of the incident surface 11 and the
reflected wave reflected on the back surface of the incident surface 11 cancel each other out The
reflectance of the incident wave on the incident surface 11 can be reduced. The acoustic Fresnel
lens 1 reduces the reflection at the incident surface 11 of the ultrasonic wave incident from the
incident surface 11 by setting the thickness D1 of the first lens 10 to a quarter of the wavelength
λ of the incident wave, thereby making the ultrasonic wave Can improve the focusing efficiency
of
[0027]
As shown in W1 area | region of FIG. 4, the convex part 7 is provided in the 1st lamination |
stacking surface 12. As shown in FIG. The convex part 7 has a triangular shape which protrudes
upwards in an II arrow direction cross section. The convex portion 7 is disposed between the
lowermost portion of the lens surface 5A of the prism 5 and the lowermost portion of the nonlens surface 5B of another adjacent prism 5. In the present embodiment, the convex portion 7
has a surface parallel to the lens surface 5A and a surface parallel to the non-lens surface 5B. The
height at which the convex portion 7 protrudes upward is the length in the vertical direction of
the prism 5, which is smaller than the height L1 in the direction in which the lens surface 5A
faces. In the convex portion 7, when the first lens 10 and the second lens 20 are laminated, the
adhesive 8 described later applied to the lens surface 5A does not flow toward the non-lens
surface 5B of the adjacent prism 5 It acts as an adhesive reservoir. The prism 5 has a width M1
which is a length in the left-right direction.
[0028]
The structure of the second lens 20 will be described with reference to FIGS. 5 and 6. As shown
in FIGS. 5 and 6, the second lens 20 is a second laminated surface in which a plurality of prisms
6 including a lens surface 6A and a non-lens surface 6B are concentrically arranged around the
optical center C2. 22 is equipped. The second laminated surface 22 is a surface laminated on the
first laminated surface 12 of the first lens 10, and is a surface disposed inside the acoustic
Fresnel lens 1. In the present embodiment, the second lens 20 is made of silicone resin, but may
be made of other synthetic resin. The second lens 20 can be obtained by injection molding a raw
material of silicone resin into a mold not shown.
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[0029]
The acoustic impedance of the second lens 20 made of silicone resin is approximately 1.2 × 10
6 <6> N · s / m 3. The first lens 10 and the second lens 20 have different acoustic impedances.
Sound waves are refracted as they propagate between media of different acoustic impedances.
Since the acoustic Fresnel lens 1 has different acoustic impedances between the first lens 10 and
the second lens 20, it is possible to exert a lens effect of refracting sound waves. Also, the
acoustic impedance of the silicone resin approximates the acoustic impedance of water. The
acoustic impedance of water is about 1.5 × 10 6 <6> N · s / m 3. The acoustic impedance of
water approximates the acoustic impedance of the human body. For this reason, when the
ultrasonic transducer 100 is used for a deep tactile probe or the like of an ultrasonic diagnostic
apparatus, the ultrasonic wave emitted from the emission surface 21 of the acoustic Fresnel lens
1 made of silicone resin is hardly reflected at the boundary with the human body .
[0030]
As shown in FIG. 5, the lens surface 6A is formed as an annular surface concentrically arranged
at the same predetermined pitch as that of the plurality of lens surfaces 5A in the first lens 10 in
plan view. The plurality of prisms 6 are arranged with their apexes directed downward. At a
central portion in plan view of the second laminated surface 22, a central convex portion 23
which is a portion raised to the same position in the vertical direction as the apexes of the
plurality of prisms 6 is provided. As shown in FIG. 6, the lens surface 6 </ b> A is inclined
obliquely upward with respect to the bottom surface of the central convex portion 23 around the
central convex portion 23. The angle at which the lens surface 6A is inclined with respect to the
bottom surface of the central convex portion 23 is an angle approximating a curved surface
having a radius of curvature corresponding to the focal length of the second lens 20. The lens
surfaces 6A are arranged concentrically at a predetermined pitch with such an angle, and the
output surface 21 which is the opposite surface of the second laminated surface 22 is formed
flat. The two lenses 20 can function as plano-convex lenses. In other words, the lens surface 6A is
a surface that acts as a lens in the second lens 20. In the present embodiment, the lens surface
6A is a flat surface, but the lens surface 6A may have a curved surface.
[0031]
The non-lens surface 6B is a surface that connects the lower end of the lens surface 6A and the
second laminated surface 22. In the present embodiment, the non-lens surface 6B is a plane
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extending vertically in the vertical direction, but the non-lens surface 6B may have a curved
surface. In addition, the non-lens surface 6B is not limited to a plane extending in the vertical
direction, and may be a slope inclined with respect to the vertical direction. The non-lens surface
6B is a surface having an angle different from that of the lens surface 6A, and in the second lens
20, it is a surface that does not act directly as a lens.
[0032]
In the second laminated surface 22, positioning pins 40, 40 are provided at the edge where the
plurality of prisms 6 are not disposed, which are portions projecting downward to approximately
the same position in the vertical direction as the apexes of the plurality of prisms 6. It is done.
The positioning pins 40 are disposed on a II-II straight line parallel to the left-right direction
passing through the optical center C2 shown in FIG. When the first laminated surface 12 of the
first lens 10 and the second laminated surface 22 of the second lens 20 are laminated such that
the positioning pins 40, 40 fit in the receiving portions 30, a plurality of acoustic Fresnel lenses
1 are obtained. The plurality of prisms 6 are alternately arranged between each of the prisms 5
(see FIG. 10).
[0033]
The thickness D2 of the second lens 20 shown in FIG. 6 is, for example, 0.3 mm. The thickness
D2 is about one fourth of the wavelength λ of the ultrasonic wave incident on the second lens
20 from the lens surface 6A. The acoustic Fresnel lens 1 reduces the reflection of the ultrasonic
wave incident from the lens surface 6A at the lens surface 6A by setting the thickness D2 of the
second lens 20 to a quarter of the wavelength λ of the incident wave, thereby making the
ultrasonic wave Can improve the focusing efficiency of
[0034]
As shown in the W2 area of FIG. 6, the prism 6 has a length L2 in the vertical direction, a height
L2 in the direction in which the lens surface 6A faces, and a width M2 as the length in the
horizontal direction. In the present embodiment, the height L1 of the prism 5 (see the W1 area in
FIG. 4) is longer than the height L2 of the prism 6. Also, the width M 1 of the prism 5 is longer
than the width M 2 of the prism 6. In other words, the prism 5 is configured to be larger than the
prism 6. The first lens 10 initially enters the ultrasonic wave generated by the piezoelectric
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element 2 and emits the incident ultrasonic wave to the second lens 20. Therefore, as the size of
the lens surface 5A from which the ultrasonic waves are emitted in the first lens 10 is larger, the
acoustic Fresnel lens 1 can efficiently transmit the ultrasonic waves to the second lens 20. In the
acoustic Fresnel lens 1, the prism 5 is configured to be larger than the prism 6, so that the lens
surface 5 A is secured larger than in the case where the sizes of the prism 5 and the prism 6 are
the same.
[0035]
The manufacturing process of the acoustic Fresnel lens 1 will be described with reference to
FIGS. 7 to 10. As shown in FIG. 7, the manufacturing process of the acoustic Fresnel lens 1
includes a coating process (S1), a positioning process (S2), and a bonding process (S3).
[0036]
First, the application step (S1) will be described. As shown in FIG. 8, in the coating step, the
adhesive 8 is applied to the lens surface 5 </ b> A of the acoustic lens 10. For example, a spin
coating method is employed in the step of applying the adhesive 8 to the lens surface 5A.
Specifically, the first lens 10 is attached to a spinner (not shown) with the first laminated surface
12 up. Next, a predetermined amount of adhesive 8 is dropped onto the central recess 13 of the
first laminated surface 12 by a known dispenser (not shown). Thereafter, by rotating the spinner
at high speed, the first lens 10 is rotated at high speed about the optical center C1. At this time,
the adhesive 8 dropped to the central recess 13 is drawn by the centrifugal force of the high
speed rotation of the first lens 10 and spread on the lens surface 5 A around the central recess
13. Further, a part of the adhesive 8 spread on the lens surface 5A is conveyed to the lens
surface 5A adjacent to the outside through the upper end portion of the lens surface 5A. At this
time, since the adhesive 8 is carried to the adjacent lens surface 5A by the centrifugal force of
the high speed rotation of the first lens 10, the adhesive 8 is hard to adhere to the non-lens
surface 5B. Further, as shown in the W3 region of FIG. 8, the convex portion 7 stores the
adhesive 8 applied to the lens surface 5A on the lens surface 5A, and the adhesive 8 is directed
toward the adjacent non-lens surface 5B. Prevent it from flowing. The adhesive 8 can be
uniformly applied to the plurality of lens surfaces 5A of the first laminated surface 12 by
determining the appropriate amount of the adhesive 8 and the rotation speed of the appropriate
spinner through prior experiments and the like.
[0037]
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Next, the positioning step (S2) will be described. As shown in FIG. 9, in the positioning step, in
order to laminate the second lens 20 to the first lens 10 having the adhesive 8 applied to the lens
surface 5A in the application step of the adhesive 8, the first lens 10 And the second lens 20 are
mutually positioned. In this positioning step, with respect to the first laminated surface 12 of the
first lens 10, at positions where the positioning pins 40, 40 of the second laminated surface 22
engage with the receiving portions 30, 30 of the first laminated surface 12, The second
laminated surface 22 of the second lens 20 is disposed to face each other. At this time, the first
lens 10 and the second lens 20 are positioned between the plurality of prisms 5 such that the
plurality of prisms 6 are alternately arranged. After this positioning is performed, the second lens
20 is moved relative to the first lens 10 in the direction indicated by the arrow Y, and the
positioning pins 40 are inserted into the receiving portions 30. The receiving portions 30, 30
receive and abut the positioning pins 40, 40 inside. Moreover, the receiving parts 30 and 30 can
be fixed so that the 1st lens 10 and the 2nd lens 20 after laminating | stacking may not shift |
deviate by fitting with the positioning pins 40 and 40. FIG.
[0038]
Next, the bonding step (S3) will be described. As shown in FIG. 10, in the bonding step, the first
lens 10 and the second lens 20 are bonded in the arrangement positioned in the positioning step.
At this time, since each of the plurality of prisms 6 is alternately disposed between each of the
plurality of prisms 5, the lens surface 5A of the prism 5 and the lens surface 6A of the prism 6
disposed opposite to the lens surface 5A Are adhered by the adhesive 8. In the present
embodiment, the pitch at which the lens surfaces 5A are arranged and the pitch at which the lens
surfaces 6A are arranged are the same. Further, since the size of the prism 5 is larger than the
size of the prism 6, when the lens surface 5A and the lens surface 6A are bonded, the non-lens
surface 5B and the non-lens surface 6B form a predetermined gap. Separate. Air enters the gap
between the non-lens surface 5B and the non-lens surface 6B, and an air layer 90 is formed. The
first lens 10 and the second lens 20 stacked in such an arrangement become integral by curing
the adhesive 8, and the manufacturing process of the acoustic Fresnel lens 1 is completed.
Various adhesives can be employed as the adhesive 8, and those that cure by reaction of
adhesive components may be used, those that cure by heat treatment may be used, and light
such as UV light may be used. Energy curing may be used.
[0039]
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As shown in the W4 area of FIG. 10, the adhesive 8 cured between the lens surface 5A and the
lens surface 6A forms an adhesive layer 80 between the lens surface 5A and the lens surface 6A.
In the acoustic Fresnel lens 1, when the adhesive 8 is cured to form the adhesive layer 80, the
acoustic impedance of the adhesive layer 80 is between the acoustic impedance of the first lens
10 and the acoustic impedance of the second lens 20. The adhesive 8 which becomes an acoustic
impedance of In the present embodiment, the adhesive 8 is a silicone adhesive. The acoustic
impedance of the adhesive 8 is about 1.2 × 10 6 <6> N · s / m 3, which is the same as that of the
second lens 20. Thus, the acoustic Fresnel lens 1 intervenes between the lens surface 5A of the
first lens 10 and the lens surface 6A of the second lens 20 with the adhesive layer 80 having an
acoustic impedance different from that of the first lens 10. Let Therefore, the ultrasonic wave
emitted from the lens surface 5A to the adhesive layer 80 is easily refracted at the interface
between the lens surface 5A and the adhesive layer 80. Further, the ultrasonic waves
propagating through the adhesive layer 80 are incident on the lens surface 6A in a state where
the reflection at the interface with the lens surface 6A is reduced. The acoustic Fresnel lens 1 has
its acoustic impedance gradually lowered from the incident side to the outgoing side of the
ultrasonic wave, so that it is incident from the incident surface 11 and propagates through the
lens surfaces 5A, 6A and the adhesive layer 80. Can be focused while being refracted inside, and
can be emitted from the emission surface 21.
[0040]
Here, if the acoustic Fresnel lens 1 is entirely composed of a single medium, as described above,
the ultrasonic waves can not be focused while gradually increasing the refractive index of the
ultrasonic waves inside. The acoustic Fresnel lens 1 has a plurality of boundary surfaces of media
having different acoustic impedances in its inside, thereby controlling the degree of refraction of
the ultrasonic wave for each boundary surface, and thus the ultrasonic refractive index of the
acoustic Fresnel lens 1 It can be adjusted as desired. Also, by making it possible to adjust the
ultrasonic refractive index, the acoustic Fresnel lens 1 can improve the lens effect of the acoustic
Fresnel lens 1 rather than forming the entire lens with a single medium.
[0041]
In the acoustic Fresnel lens 1, in order to adjust the ultrasonic refractive index to a desired one, it
is desirable that the thickness of the adhesive layer 80 be uniform. In order to form the adhesive
layer 80 having a uniform thickness, it is preferable that the lens surface 5A and the lens surface
6A, which are disposed opposite to each other, be formed in parallel.
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[0042]
Here, the acoustic impedance of the air layer 90 is approximately 0.0004 × 10 6 <6> N · s / m 3.
The acoustic impedance of the air layer 90, which is a gas layer, is very low compared to the
acoustic impedance of the first lens 10, the adhesive layer 80, and the second lens 20. The nonlens surface 5B is a surface which does not act as a direct lens in the first lens 10, but a part of
the ultrasonic wave that has propagated inside the first lens 10 and reached the non-lens surface
5B is emitted from the non-lens surface 5B. there's a possibility that. The ultrasonic wave emitted
from the non-lens surface 5B does not reach the focal point of the first lens 10 because the
emission angle is different from the ultrasonic wave emitted from the lens surface 5A and does
not contribute to the focusing of the ultrasonic wave by the acoustic Fresnel lens 1 . In addition,
there is a possibility that ultrasonic waves emitted from the non-lens surface 5B may be incident
from the non-lens surface 6B disposed to face the non-lens surface 5B. The non-lens surface 6B is
a surface which does not act as a direct lens in the second lens 20, and the ultrasonic wave
incident from the non-lens surface 6B has a different incident angle from the ultrasonic wave
incident from the lens surface 6A. For this reason, the ultrasonic wave incident from the non-lens
surface 6 B does not reach the focal point of the second lens 20, repeats reflection inside the
second lens 20, and does not contribute to the focusing of the ultrasonic wave by the acoustic
Fresnel lens 1.
[0043]
The acoustic Fresnel lens 1 has an air layer 90 having a very low acoustic impedance as
compared to the acoustic impedance of the non-lens surfaces 5B and 6B between the non-lens
surface 5B and the non-lens surface 6B which do not function as such a lens. Is provided. Thus,
the acoustic Fresnel lens 1 can make it difficult for the ultrasonic wave to be emitted from the
non-lens surface 5B. Further, even if ultrasonic waves are emitted from the non-lens surface 5B
to the air layer 90, the ultrasonic waves are different from the air layer 90 to the non-lens
surface because the acoustic impedance is very different between the air layer 90 and the nonlens surface 6B. It is difficult to enter 6B. Therefore, by providing the air layer 90 between the
non-lens surface 5B and the non-lens surface 6B, the acoustic Fresnel lens 1 reduces the
possibility of propagation of ultrasonic waves not contributing to focusing inside the acoustic
Fresnel lens 1. , Ultrasonic focusing performance can be improved.
[0044]
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In the acoustic Fresnel lens 1, in order to prevent the propagation of ultrasonic waves that do not
contribute to focusing through the non-lens surface 5B and the non-lens surface 6B, it is
desirable that the air layer 90 maintain a predetermined thickness. In order to form the air layer
90 maintaining a predetermined thickness, it is preferable that the non-lens surface 5B and the
non-lens surface 6B, which are disposed opposite to each other, be formed in parallel.
[0045]
As shown in the W4 area of FIG. 10, the acoustic Fresnel lens 1 is disposed such that the upper
portion of the convex portion 7 is in contact with the lowermost apex of the prism 6. Therefore,
the convex portion 7 prevents the adhesive 8 from flowing into the air layer 90 until the
adhesive 8 is completely cured, thereby separating the adhesive layer 80 and the air layer 90. . In
the bonding step, if the adhesive 8 flows into the air layer 90, the adhesive layer 80 is also
formed between the non-lens surface 5B and the non-lens surface 6B, and ultrasonic waves that
do not contribute to focusing do not form the non-lens surface 5B. And may be easily propagated
through the non-lens surface 6B. Conversely, when air in the air layer 90 flows into the adhesive
layer 80, the propagation of ultrasonic waves from the lens surface 5A to the lens surface 6A
through the adhesive layer 80 may be hindered. In order to prevent such an event, the acoustic
Fresnel lens 1 can reliably separate the adhesive layer 80 and the air layer 90 in the bonding
process to improve the focusing performance of ultrasonic waves in the acoustic Fresnel lens 1.
[0046]
As described above, in the acoustic Fresnel lens 1, the ultrasonic wave incident from the incident
surface 11 of the first lens 10 is emitted from the emission surface 21 of the second lens 20. The
first lens 10 and the second lens 20 are laminated on the first laminated surface 12 and the
second laminated surface 22 via the adhesive layer 80. The adhesive layer 80 can transmit the
ultrasonic wave emitted from the lens surface 5A of the prism 5 to the lens surface 6A of the
prism 6 oppositely disposed. On the other hand, the acoustic impedance in the air layer 90 is
much smaller than that in the first lens 10 and the second lens 20. Therefore, the ultrasonic wave
emitted from the non-lens surface 5B of the prism 5 is attenuated in the air layer 90 and hardly
enters from the non-lens surface 6B of the prism 6. In this manner, the acoustic Fresnel lens 1
can form an air layer 90 that can effectively prevent the leakage of ultrasonic waves, and can
efficiently focus the ultrasonic waves.
14-04-2019
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[0047]
Ultrasonic waves are refracted at the interface of media having different acoustic impedances.
The first lens 10 is made of acrylic resin. The second lens 20 is made of silicone resin. Since the
first lens 10 and the second lens 20 are made of materials whose acoustic impedances are
different from each other, the acoustic Fresnel lens 1 can exert a lens effect of focusing the
acoustic wave.
[0048]
The acoustic impedance of the first lens 10 is higher than the acoustic impedance of the second
lens 20. Further, the acoustic impedance of the adhesive layer 80 is lower than the acoustic
impedance of the first lens 10 and has a value similar to the acoustic impedance of the second
lens 20. Since the acoustic Fresnel lens 1 internally has interfaces of media having different
acoustic impedances, the refractive index of the sound wave can be controlled for each interface.
In addition, since the acoustic impedance gradually decreases from the first lens 10 to the second
lens 20, the acoustic Fresnel lens 1 efficiently converges the ultrasonic wave incident from the
incident surface 11 and emits it from the emission surface 21. it can.
[0049]
Since the adhesive layer 80 and the air layer 90 are separated by the convex portion 7, for
example, the air of the air layer 90 flows into the adhesive layer 80, and the transmission of
ultrasonic waves from the lens surface 5A to the lens surface 6A is It is possible to reduce the
possibility of the air layer 90 being blocked by air. Therefore, the acoustic Fresnel lens 1 can
efficiently transmit ultrasonic waves from the first lens 10 to the second lens 20.
[0050]
The convex portion 7 is provided on the first laminated surface 12 and protrudes from the first
laminated surface 12 toward the apex of the prism 6. Therefore, the acoustic Fresnel lens 1 can
reliably separate the adhesive layer 80 and the air layer 90 at the convex portion 7.
14-04-2019
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[0051]
The acoustic Fresnel lens 1 can prevent the first lens 10 and the second lens 20 from being
deviated from being stacked by fitting the positioning pins 40 into the receiving portions 30, 30.
[0052]
The acoustic Fresnel lens 1 secures the lens surface 5A larger by making the height L1 of the
prism 5 larger than the height L2 of the prism 6, compared to making the sizes of the prism 5
and the prism 6 equal. Ultrasonic waves can be focused efficiently.
[0053]
In the acoustic Fresnel lens 1, the thickness D1 of the first lens 10 and the thickness D2 of the
second lens 20 are respectively about one fourth of the wavelength of the ultrasonic wave
incident on the first lens 10 and the second lens 20. Thus, it is possible to effectively prevent the
reflection of ultrasonic waves incident on the first lens 10 and the second lens 20.
[0054]
In the present embodiment, the acoustic Fresnel lens 1 corresponds to the “acoustic Fresnel
lens” of the present invention, the first lens 10 corresponds to the “first Fresnel lens” of the
present invention, and the second lens 20 corresponds to the present invention. Corresponds to
the “second Fresnel lens” of
The incident surface 11 corresponds to the "incident surface" of the present invention, and the
first laminated surface 12 corresponds to the "first laminated surface" of the present invention.
The second laminated surface 22 corresponds to the “second laminated surface” of the
present invention, and the emitting surface 21 corresponds to the “emitting surface” of the
present invention.
The prism 5 corresponds to the "first prism" of the present invention, the lens surface 5A
corresponds to the "first lens surface" of the present invention, and the non-lens surface 5B
corresponds to the "first non-lens surface" of the present invention It corresponds to The prism 6
corresponds to the "second prism" of the present invention, the lens surface 6A corresponds to
the "second lens surface" of the present invention, and the non-lens surface 6B corresponds to
14-04-2019
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the "second non-lens surface" of the present invention It corresponds to The adhesive layer 80
corresponds to the “adhesive layer” of the present invention, and the air layer 90 corresponds
to the “air layer” of the present invention. The convex portion 7 corresponds to the "separating
member" of the present invention, and the receiving portions 30, 30 and the positioning pins 40,
40 correspond to the "positioning means" of the present invention.
[0055]
The present invention is not limited to the above embodiment. A modification of the present
invention will be described with reference to FIG. The acoustic Fresnel lens 200 of the modified
example is formed by laminating a first lens 110 and a second lens 120. The acoustic Fresnel
lens 200 is replaced with the receiving portions 30, 30 and the positioning pins 40, 40 provided
in the acoustic Fresnel lens 1 of the above embodiment, and the positioning portions 130, 130
and the contact portion 140 where the positioning portions 130, 130 contact. , 140. As shown in
FIG. 11, the positioning portions 130, 130 are provided at the left and right end portions of the
first lens 110, and the upper end portion is a protruding portion that protrudes upward beyond
the first laminated surface 12. The upper end portions of the positioning portions 130 and 130
are disposed at positions where the second lens 120 can be held from outside the outer diameter
of the second lens 120. The abutting portions 140 and 140 are both left and right end portions
of the second lens 120, and the inner side of the positioning portions 130 and 130 and the
abutting portion 140 in a state where the first lens 110 and the second lens 120 are laminated. ,
140 abut on each other to position the laminated position of the first lens 110 and the second
lens 120. As described above, the positioning means for positioning the laminated position of the
first lens 10 and the second lens 20 is not limited to the receiving portions 30 and 30 and the
positioning pins 40 and 40 in the above embodiment, and various methods are adopted. May be
done. In the modification, the positioning portions 130, 130 and the contact portions 140, 140
correspond to the "positioning means" of the present invention.
[0056]
The member for separating the adhesive layer 80 and the air layer 90 in the acoustic Fresnel lens
1 is not limited to the convex portion 7 provided on the first laminated surface 12 in the above
embodiment. As shown in the W5 region of FIG. 11, the acoustic Fresnel lens 200 in the
modification is a member for separating the adhesive layer 80 and the air layer 90, and is a
convex portion instead of the convex portion 7 of the above embodiment. 70 is provided. The
protrusion 70 is a protrusion extending downward from the top of the prism 6. The lower end
portion of the convex portion 70 abuts on the lower end portion of the lens surface 5A of the
14-04-2019
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prism 5 in a state where the first lens 10 and the second lens 20 are laminated. Thereby, the
convex part 70 can isolate the adhesive layer 80 and the air layer 90 reliably. Thus, a member
for separating the adhesive layer 80 and the air layer 90 may be provided on the second
laminated surface 22. In addition to this, a member for separating the adhesive layer 80 and the
air layer 90 may be provided on both the first laminated surface 12 and the second laminated
surface 22. That is, a member for separating the adhesive layer 80 and the air layer 90 may be
provided on at least one of the first lamination surface 12 and the second lamination surface 22.
In the modification, the convex portion 70 corresponds to the "separating member" of the
present invention.
[0057]
The present invention is not limited to the above embodiments and modifications, and various
modifications are possible. For example, the outer shape of the acoustic Fresnel lens 1 in a plan
view is not limited to a circle, and may be, for example, a rectangle. Further, in the acoustic
Fresnel lens 1, the plurality of prisms 5 and 6 may not be arranged concentrically with respect to
the optical centers C 1 and C 2 of the first lens 10 and the second lens 20. It may be done. That
is, the acoustic Fresnel lens 1 may be a linear Fresnel lens.
[0058]
In the said embodiment, although the output surface 21 of the acoustic Fresnel lens 1 is a plane,
the shape of the output surface 21 is not restricted to this. For example, the exit surface 21 may
have a curved surface. In this case, since the exit surface 21 acts as a convex lens, the focusing
effect of the ultrasonic waves by the acoustic Fresnel lens 1 can be further improved.
[0059]
In the above embodiment, the thickness D1 of the first lens 10 and the thickness D2 of the
second lens 20 are respectively about one fourth of the wavelength of the ultrasonic wave
incident on the first lens 10 and the second lens 20. For example, the thickness D1 of the first
lens 10 and the thickness D2 of the second lens 20 may be odd multiples of about one fourth of
the wavelength λ of the incident wave incident on the first lens 10 and the second lens 20,
respectively. . Even in this case, the acoustic Fresnel lens 1 can reduce the reflection of the
ultrasonic waves incident on the first lens 10 and the second lens 20 to improve the focusing
14-04-2019
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efficiency.
[0060]
In the above embodiment, the adhesive 8 capable of forming the adhesive layer 80 having the
same acoustic impedance as the second lens 20 is used. The acoustic impedance of the adhesive
layer 80 is not limited to the same as that of the second lens 20, and the adhesive layer 80 may
have an acoustic impedance between the acoustic impedance of the first lens 10 and the acoustic
impedance of the second lens 20. You may have. In this case, since the acoustic Fresnel lens 1
can have a plurality of interfaces of media having different acoustic impedances inside, the
refractive index of the sound wave can be controlled for each interface.
[0061]
The incident wave incident on the acoustic Fresnel lens 1 is not limited to the ultrasonic wave,
and may be a sound wave having a frequency lower than that of the ultrasonic wave. The
acoustic Fresnel lens 1 can enter, for example, a sound wave in the audible range of human
beings from the incident surface 11, focus it internally, and emit it from the outgoing surface 21.
[0062]
1,200 acoustic Fresnel lens 5, 6 prism 5A, 6A lens surface 5B, 6B non-lens surface 7, 70 convex
part 8 adhesive 10, 110 first lens 11 incident surface 12 first laminated surface 20, 120 second
lens 21 Output surface 22 Second laminated surface 30, 30 Receiving portion 40, 40 Positioning
pin 80 Adhesive layer 90 Air layer 130, 130 Positioning portion 140, 140 Contact portion
14-04-2019
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