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JP2008258864

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DESCRIPTION JP2008258864
The present invention provides an electrostatic ultrasonic transducer capable of holding a
vibrating membrane with a pair of electrodes with an equal force and obtaining stable membrane
vibration. A first electrode having a through hole, a second electrode having a through hole, and
the through hole of the first electrode and the through hole of the second electrode are paired. A
vibrating membrane disposed between and sandwiched by a pair of electrodes consisting of the
first electrode and the second electrode and having a conductive layer, to which a DC bias voltage
is applied to the conductive layer; The convex portion of the plate-like fixing member having a
convex shape is brought into contact with the vicinity of the central portion of the surface on the
opposite side to the vibrating film of any one of the electrodes, and the plate-like fixing member
and the A pair of electrodes is integrally fixed, and a modulation wave obtained by modulating a
carrier wave in an ultrasonic frequency band with a signal wave in an audio frequency band is
applied between the pair of electrodes. [Selected figure] Figure 1
Electrostatic ultrasonic transducer, ultrasonic speaker, sound signal reproducing method for
electrostatic ultrasonic transducer, display device, and directional acoustic system
[0001]
The present invention relates to an electrostatic ultrasonic transducer used for a directional
sharp acoustic radiation device, and more particularly to an electrostatic ultrasonic transducer
capable of obtaining stable film vibration, and the electrostatic ultrasonic transducer. The present
invention relates to an ultrasonic speaker including a transducer, an audio signal reproduction
method of an electrostatic ultrasonic transducer, a display including an ultrasonic speaker, and a
directional acoustic system.
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[0002]
Piezoelectric and electrostatic transducers have been proposed as ultrasonic transducers for use
in directional acoustic radiation devices.
The piezoelectric ultrasonic transducer has a defect that the resonance point is sharp and it is
difficult to widen the band, so that the sound reproducibility is poor (see, for example, Patent
Documents 1 and 2).
[0003]
On the other hand, in the electrostatic ultrasonic transducer, the resonance of the vibrating
membrane itself is not sharp, and by using the air column resonance phenomenon of the sound
tube, the band can be broadened and the sound reproducibility is excellent (good sound quality)
It has the advantage of (see, for example, Patent Document 3).
[0004]
FIG. 13 shows a prior art electrostatic ultrasonic transducer 3.
FIG. 13A shows a cross section of the electrostatic ultrasonic transducer 3. The electrostatic
ultrasonic transducer 3 includes the vibrating film 30 having the vibrating electrode (electrode
layer) 32 and the vibrating film 30. It has a pair of fixed electrodes consisting of a front side fixed
electrode 60A and a back side fixed electrode 60B provided facing each other on the surface. The
vibrating film 30 is formed so as to sandwich a vibrating electrode (electrode layer) 32 forming
an electrode between dielectric films (insulation films) 31 and 33.
[0005]
Further, a plurality of through holes 61A are provided in the front side fixed electrode 60A
sandwiching the vibrating film 30, and positions facing the respective through holes 61A
provided in the front side fixed electrode 60A in the back side fixed electrode 60B. The throughhole 61B of the same shape is provided in. The front side fixed electrode 60A and the back side
fixed electrode 60B are respectively supported by the supporting member 62 with a
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predetermined gap from the vibrating membrane 30, and the vibrating membrane 30 and the
fixed electrode partially oppose each other via a gap. Thus, the support member 62 is formed.
FIG. 13 (B) shows a one-side plan view of the transducer, in which a plurality of through holes
61A are arranged in a honeycomb shape on the front side fixed electrode 60A.
[0006]
The DC power supply 36 is a power supply for applying a DC bias voltage to the vibrating
electrode 32, and the AC signals 37A and 37B are applied to the front fixed electrode 60A and
the rear fixed electrode 60B to drive the vibrating film 30. It is a signal to be applied. With the
above configuration, the front fixed electrode 60A and the back fixed electrode 60B of the
electrostatic ultrasonic transducer 3 have the same amplitude on the basis of the center tap, and
the alternating current signal 37A whose phase is reversed to each other. 37B is applied.
[0007]
In this way, the direction in which the electrostatic force acts alternately changes while the
vibrating membrane 30 is subjected to electrostatic attraction and electrostatic repulsion in the
same direction according to the change in polarity of the AC signal, so that large membrane
vibration, ie, It is possible to generate an acoustic signal of sufficient sound pressure level to
obtain a parametric array effect. As described above, in the electrostatic ultrasonic transducer 3
shown in FIG. 10, since the vibrating film 30 vibrates by receiving force from the pair of fixed
electrodes 60A and 60B, a push-pull (Push-Pull) type electrostatic It is called an ultrasonic
transducer. JP-A-61-296897 JP-A-2000-287297 JP-A-2006-93932
[0008]
The above-described electrostatic ultrasonic transducer has an advantage of being able to be
broadened in bandwidth and excellent in sound reproducibility (good sound quality) as compared
with a resonant ultrasonic transducer.
[0009]
However, in this electrostatic ultrasonic transducer, due to its structure, it is difficult to press the
vibrating film with a uniform force with a pair of electrodes, and as a result, a gap is generated
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between the pair of electrodes, etc. It was difficult to hold the vibrating film with uniform force
and uniform distance with the electrodes.
In the electrostatic ultrasonic transducer, it is necessary to release high acoustic energy into the
air by causing the vibrating film to stably oscillate in the same manner. However, in the case of a
conventional electrostatic ultrasonic transducer, the vibration is generated. There was a limit to
the stable vibration of the membrane.
[0010]
The present invention has been made in view of such circumstances, and an electrostatic
ultrasonic transducer capable of holding a vibrating membrane with a pair of electrodes with
equal force and obtaining stable membrane vibration, and the electrostatic type ultrasonic
transducer. It is an object of the present invention to provide an ultrasonic speaker including an
acoustic transducer, a method of reproducing an audio signal of an electrostatic ultrasonic
transducer, a display device including an ultrasonic speaker, and a directional acoustic system.
[0011]
In order to achieve the above object, according to an electrostatic ultrasonic transducer of the
present invention, a first electrode having a through hole, a second electrode having a through
hole, and the through hole of the first electrode are provided. And the through hole of the second
electrode are arranged in a pair and are sandwiched between a pair of electrodes consisting of
the first electrode and the second electrode, and have a conductive layer, and the conductive
layer A vibrating membrane to which a DC bias voltage is applied, and a plate-like fixing having a
convex shape in the vicinity of the central portion of the surface of either one of the pair of
electrodes opposite to the vibrating membrane. The plate-like fixing member and the pair of
electrodes are integrally fixed so that the convex portion of the member abuts, and the carrier
wave of the ultrasonic frequency band is audible between the pair of electrodes. It is
characterized in that a modulation wave modulated by a band signal wave is applied.
With the above configuration, the back center of one of the pair of electrodes sandwiching the
diaphragm contacts the convex portion of the plate-like fixing member, and the peripheral
portion of the pair of electrodes is screwed by the plate-like fixing member. It is fixed so that it
can be pressed down with. As a result, the pair of electrodes in the electrostatic ultrasonic
transducer is configured such that the acoustic emission surface is slightly convex, and as a
result, a substantially uniform force is applied between the pair of electrodes, and the vibrating
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membrane has a uniform force. It is held at (distance) and stable membrane vibration can be
obtained.
[0012]
Further, in the electrostatic ultrasonic transducer according to the present invention, the platelike fixing member is a member of the plate-like fixing member which is in contact with the
surface of either one of the pair of electrodes opposite to the vibrating membrane. It is
characterized in that the surface is formed into a convex curved surface. With the above
configuration, the back center of one of the pair of electrodes sandwiching the diaphragm
contacts the convex surface of the plate-like fixing member, and the peripheral portion of the
pair of electrodes is screwed by the plate-like fixing member. It is fixed so as to be held down. As
a result, the pair of electrodes in the electrostatic ultrasonic transducer is configured such that
the acoustic emission surface is slightly convex, and as a result, a substantially uniform force is
applied between the pair of electrodes, and the vibrating film has a uniform force (distance). And
stable membrane vibration is obtained.
[0013]
Further, in the electrostatic ultrasonic transducer according to the present invention, the platelike fixing member is a member of the plate-like fixing member which is in contact with the
surface of either one of the pair of electrodes opposite to the vibrating membrane. It is
characterized in that it has a protrusion at the center of the surface. With the above
configuration, the back center of one of the pair of electrodes sandwiching the diaphragm
contacts the protrusion formed at the center of the plate-like fixing member, and the peripheral
portion of the pair of plates is the plate-like. It is fixed so that it can be pressed down by a screw
etc. by a fixing member. As a result, the pair of electrodes in the electrostatic ultrasonic
transducer is configured such that the acoustic emission surface is slightly convex, and as a
result, a substantially uniform force is applied between the pair of electrodes, and the vibrating
film has a uniform force (distance ) And stable membrane vibration can be obtained.
[0014]
Further, according to the electrostatic ultrasonic transducer of the present invention, a first
electrode having a slit-like through hole, a second electrode having a slit-like through hole, the
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through hole of the first electrode, and The through hole of the second electrode is disposed in a
pair, and is sandwiched by a pair of electrodes consisting of the first electrode and the second
electrode, and has a conductive layer, and the conductive layer A vibrating membrane to which a
DC bias voltage is applied, and the pair of electrodes have an electrode layer disposed in the
longitudinal direction of the through hole inside the through hole, any of the pair of electrodes
The convex portion of the plate-like fixing member having a convex shape is brought into contact
with the vicinity of the central portion of the surface of the one electrode opposite to the
vibrating film so that the plate-like fixing member and the pair of And the electrodes of the pair
of electrodes. Pole in the interlayer, characterized in that the modulated wave obtained by
modulating the carrier wave in the ultrasonic frequency band by signal waves in the audio
frequency band is applied. With the above configuration, the back center of one of the pair of
electrodes sandwiching the diaphragm is in contact with the convex portion of the plate-like
fixing member, and the peripheral portion of the pair of electrodes is screwed by the plate-like
fixing member. It is fixed so that it can be pressed down by. As a result, the pair of electrodes in
the electrostatic ultrasonic transducer is configured such that the acoustic emission surface is
slightly convex, and as a result, a substantially uniform force is applied between the pair of
electrodes, and the vibrating film has a uniform force (distance). And stable membrane vibration
is obtained.
[0015]
Further, in the electrostatic ultrasonic transducer according to the present invention, the platelike fixing member is a member of the plate-like fixing member which is in contact with the
surface of either one of the pair of electrodes opposite to the vibrating membrane. It is
characterized in that the surface is formed into a convex curved surface. With the above
configuration, the back center of one of the pair of electrodes sandwiching the diaphragm
contacts the convex surface of the plate-like fixing member, and the peripheral portion of the
pair of electrodes is screwed by the plate-like fixing member. It is fixed so as to be held down. As
a result, the pair of electrodes in the electrostatic ultrasonic transducer is configured such that
the acoustic emission surface is slightly convex, and as a result, a substantially uniform force is
applied between the pair of electrodes, and the vibrating film has a uniform force (distance). And
stable membrane vibration is obtained.
[0016]
Further, in the electrostatic ultrasonic transducer according to the present invention, the platelike fixing member is a member of the plate-like fixing member which is in contact with the
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surface of either one of the pair of electrodes opposite to the vibrating membrane. It is
characterized in that it has a protrusion at the center of the surface. With the above
configuration, the back center of one of the pair of electrodes sandwiching the diaphragm
contacts the protrusion formed at the center of the plate-like fixing member, and the peripheral
portion of the pair of plates is the plate-like. It is fixed so that it can be pressed down by a screw
etc. by a fixing member. As a result, the pair of electrodes in the electrostatic ultrasonic
transducer is configured such that the acoustic emission surface is slightly convex, and as a
result, a substantially uniform force is applied between the pair of electrodes, and the vibrating
film has a uniform force (distance ) And stable membrane vibration can be obtained.
[0017]
In the electrostatic ultrasonic transducer according to the present invention, the vibration may be
parallel to the longitudinal direction of the through hole in the through hole of the first electrode
and the through hole of the second electrode. It has a bridge portion provided with a diaphragm
facing surface facing at a predetermined distance in the depth direction of the through hole with
respect to the surface when the membrane does not vibrate, and the diaphragm facing surface of
the bridge portion An electrode layer is formed. In the electrostatic ultrasonic transducer having
the above configuration, a plurality of slit-like (rectangular) through holes are provided in each of
the pair of electrodes sandwiching the vibrating film, and are parallel to the longitudinal
direction of the through holes. The vibrating membrane facing surface of the bridge portion has a
bridge portion provided with a vibrating membrane facing surface that faces the surface of the
vibrating membrane in the non-vibrating state with a predetermined distance in the depth
direction of the through hole. Form an electrode layer. Thus, the electrode and the bridge portion
can be integrally formed, and the electrode layer can be easily formed.
[0018]
Further, in the electrostatic ultrasonic transducer according to the present invention, the first
electrode, the second electrode, and the bridge portion are formed of a nonconductive material.
In the electrostatic ultrasonic transducer of the above configuration, in the electrostatic
ultrasonic transducer of the above configuration, the first electrode, the second electrode, and the
bridge portion are formed of a nonconductive material, and An electrode layer is formed on the
vibrating film facing surface. Thus, the electrodes of the electrostatic ultrasonic transducer can
be formed of a material such as plastic, and the electrostatic ultrasonic transducer can be
manufactured in a lightweight and inexpensive manner.
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[0019]
Further, in the electrostatic ultrasonic transducer according to the present invention, a
reinforcing member which traverses the through hole in the inside of the through hole in the
lateral direction in at least one of the first electrode and the second electrode. It is characterized
by having. In the electrostatic ultrasonic transducer having the above configuration, the through
hole may be formed in the through hole in at least one of the first electrode and the second
electrode which are a pair of electrodes sandwiching a vibrating membrane. And a reinforcing
member that transverses the Thus, the strength of the electrode of the electrostatic ultrasonic
transducer can be increased, in addition to the effect of increasing the area of the opening for
emitting the acoustic signal as well as increasing the vibration area of the diaphragm. For this
reason, it is possible to manufacture an electrostatic ultrasonic transducer of a large area (for
example, 50 mm О 50 mm or more).
[0020]
In the electrostatic ultrasonic transducer according to the present invention, the vibrating
membrane is characterized in that a conductive layer is formed in multiple layers. In the
electrostatic ultrasonic transducer with the above configuration, the conductive layer (vibrating
electrode) of the vibrating film is formed in multiple layers. As a result, the electrostatic force
applied to the diaphragm can be increased, the amplitude of the diaphragm can be increased, and
the sound pressure level of the output acoustic signal can be increased.
[0021]
In the electrostatic ultrasonic transducer according to the present invention, the first electrode
having a through hole, the second electrode having a through hole, the through hole of the first
electrode, and the second electrode of the second electrode A through hole is disposed to form a
pair and is sandwiched between a pair of electrodes consisting of the first electrode and the
second electrode, and has a conductive layer, and a DC bias voltage is applied to the conductive
layer. A vibrating membrane, and the first electrode and the second electrode have a counter
electrode portion facing the vibrating membrane inside the through hole, and a pair of the
electrodes The plate-like fixing member and the pair of electrodes are brought into contact with
each other so that the convex portion of the plate-like fixing member having a convex shape
abuts on the central portion of the surface on the opposite side to the vibrating membrane of any
04-05-2019
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one electrode. Of the ultrasonic frequency band between the pair of electrodes. Modulated wave
modulation is applied to Yaria wave signal wave in the audio frequency band, characterized in
Rukoto. With the above configuration, the back center of one of the pair of electrodes
sandwiching the diaphragm is in contact with the convex portion of the plate-like fixing member,
and the peripheral portion of the pair of electrodes is screwed by the plate-like fixing member. It
is fixed so that it can be pressed down by. As a result, the pair of electrodes in the electrostatic
ultrasonic transducer is configured such that the acoustic emission surface is slightly convex, and
as a result, a substantially uniform force is applied between the pair of electrodes, and the
vibrating film has a uniform force (distance). And stable membrane vibration is obtained. Further,
in the through hole, a counter electrode portion is disposed to face the vibration region of the
vibrating membrane (a portion of the vibrating membrane facing the through hole). As a result,
the amount of film amplitude in the vibration region of the vibration film can be increased.
[0022]
Further, in the electrostatic ultrasonic transducer according to the present invention, the counter
electrode portion is a counter electrode portion having a bridge structure which bridges the
outer peripheral portion of the through hole and the inside. According to the above
configuration, in the through hole, the opposing electrode portion of the bridge structure is
disposed to bridge the outer peripheral portion and the inside of the through hole so as to face
the vibration region of the vibrating membrane (the portion of the vibrating membrane facing the
through hole). . As a result, the amount of film amplitude in the vibration region of the vibration
film can be increased.
[0023]
??? The electrostatic ultrasonic transducer of the present invention is characterized in that
the bridge structure is a cruciform structure. As a result, the amount of film amplitude in the
vibration region of the vibration film can be increased.
[0024]
The ultrasonic speaker according to the present invention modulates the carrier wave in the
ultrasonic frequency band with a signal wave output from a signal source that generates a signal
wave in the audio frequency band, and uses the modulated wave to generate an electrostatic
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ultrasonic transducer. It is an ultrasonic speaker that reproduces a signal sound in an audible
frequency band by driving a reducer, wherein the electrostatic ultrasonic transducer comprises: a
first electrode having a slit-like through hole; And the through hole of the first electrode and the
through hole of the second electrode are arranged in pairs, and the first electrode and the second
electrode And a conductive film having a conductive layer, wherein the conductive layer includes
a vibrating film to which a DC bias voltage is applied, the pair of electrodes being in the
longitudinal direction of the through hole in the through hole. Electrode layer placed on And a
convex portion of a plate-like fixing member having a convex shape is in contact with the vicinity
of the central portion of the surface of the one of the pair of electrodes opposite to the vibrating
membrane. A plate-like fixing member and the pair of electrodes are integrally fixed, and a
modulation wave obtained by modulating a carrier wave of an ultrasonic frequency band with an
audio frequency band is applied between the electrode layers of the pair of electrodes. It is
characterized by being. According to the ultrasonic speaker of the present invention configured
as described above, a carrier wave in the ultrasonic frequency band is modulated by a signal
wave in the audible frequency band, and the ultrasonic wave transducer is driven by the
modulated wave. An electrostatic ultrasonic transducer is used which has a slit-like through hole
in the electrode and has an electrode layer facing the vibrating film inside the through hole.
Thus, the vibration area of the vibrating film of the electrostatic ultrasonic transducer used for
the ultrasonic speaker can be increased, and the area of the opening for emitting the acoustic
signal can be increased. As a result, it is possible to realize an ultrasonic speaker capable of
generating an acoustic signal at a sound pressure level high enough to obtain a parametric array
effect over a wide frequency band. Further, the back center of one of the pair of electrodes
sandwiching the diaphragm of the electrostatic ultrasonic transducer used in the ultrasonic
speaker is in contact with the convex portion of the plate-like fixing member, It fixes so that the
peripheral part of an electrode may be pressed down with a screw etc. by the said plate-shaped
fixing member. As a result, the pair of electrodes in the electrostatic ultrasonic transducer is
configured such that the acoustic emission surface is slightly convex, and as a result, a
substantially uniform force is applied between the pair of electrodes, and the vibrating film has a
uniform force (distance). And stable membrane vibration is obtained.
[0025]
A sound signal reproducing method of an electrostatic ultrasonic transducer according to the
present invention comprises a first electrode having a slit-like through hole, a second electrode
having a slit-like through hole, and the penetration of the first electrode. A hole and a through
hole of the second electrode are arranged to form a pair, and are sandwiched by a pair of
electrodes consisting of the first electrode and the second electrode and having a conductive
layer, A vibrating membrane to which a direct current bias voltage is applied to the conductive
layer, the pair of electrodes including an electrode layer disposed in the longitudinal direction of
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the through hole inside the through hole, the pair of electrodes The convex portion of the platelike fixing member having a convex shape is brought into contact with the vicinity of the central
portion of the surface of the one of the electrodes opposite to the vibrating membrane so that the
plate-like fixing member and the pair of Electrostatic ultrasonic transducer which is fixed
integrally with the electrode A procedure of generating a signal wave in an audible frequency
band by a signal source, a procedure of generating a carrier wave of an ultrasonic frequency
band by a carrier wave source, and using the carrier wave as a signal in the audible frequency
band. A step of generating a modulation signal modulated by a wave, and a step of driving the
electrostatic ultrasonic transducer by applying the modulation signal between the electrode
layers of the pair of electrodes are characterized. In the sound signal reproduction method of the
electrostatic ultrasonic transducer including such a procedure, the carrier wave of the ultrasonic
frequency band is modulated by the signal wave of the audible frequency band, and the
electrostatic ultrasonic transducer is converted by the modulated wave. In an ultrasonic speaker
to be driven, an electrostatic ultrasonic transducer is used which has a slit-like through hole in
the electrode and an electrode layer facing the diaphragm inside the through hole. Thus, the
vibration area of the vibrating film of the electrostatic ultrasonic transducer used for the
ultrasonic speaker can be increased, and the area of the opening for emitting the acoustic signal
can be increased. As a result, it is possible to generate an acoustic signal with a sound pressure
level high enough to obtain a parametric array effect over a wide frequency band. Further, the
back center of one of the pair of electrodes sandwiching the diaphragm of the electrostatic
ultrasonic transducer used in the ultrasonic speaker is in contact with the convex portion of the
plate-like fixing member, It fixes so that the peripheral part of an electrode may be pressed down
with a screw etc. by the said plate-shaped fixing member. As a result, the pair of electrodes in the
electrostatic ultrasonic transducer is configured such that the acoustic emission surface is
slightly convex, and as a result, a substantially uniform force is applied between the pair of
electrodes, and the vibrating film has a uniform force (distance). And stable membrane vibration
is obtained.
[0026]
Further, the display device of the present invention modulates a carrier wave signal in an
ultrasonic frequency band with an audio signal supplied from an acoustic source, drives an
electrostatic ultrasonic transducer with the modulation signal, and thereby signals in an audible
frequency band. A display device comprising: an ultrasonic speaker for reproducing sound; and a
projection optical system for projecting an image on a projection surface, wherein the
electrostatic ultrasonic transducer of the ultrasonic speaker is a slit-like through hole. A first
electrode having a slit, a second electrode having a slit-like through hole, and the through hole of
the first electrode and the through hole of the second electrode are arranged in pairs; A
diaphragm including a conductive layer and being interposed between a pair of electrodes
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consisting of the first electrode and the second electrode, and a DC bias voltage being applied to
the conductive layer; The pole is inside the through hole It has an electrode layer arranged in the
longitudinal direction of the through hole, and a plate shape having a convex shape in the vicinity
of the central portion in the surface on the opposite side to the vibrating film of either one of the
pair of electrodes The plate-like fixing member and the pair of electrodes are integrally fixed so
that the convex portion of the fixing member abuts, and a carrier wave of an ultrasonic frequency
band is formed between the electrode layers of the pair of electrodes. A modulated wave
modulated by a signal wave in the audio frequency band is applied. In the display device having
the above configuration, an ultrasonic speaker is used which is configured of an electrostatic
ultrasonic transducer having a slit-like through hole in the electrode and an electrode layer
facing the vibrating film inside the through hole. . Then, the ultrasonic speaker reproduces the
audio signal supplied from the acoustic source. As a result, the sound signal can be reproduced
so as to be emitted from a virtual sound source formed in the vicinity of the sound wave
reflection surface such as a screen with sufficient sound pressure and wide band characteristics.
Therefore, control of the reproduction range of the sound signal can be easily performed.
Further, the back center of one of the pair of electrodes sandwiching the diaphragm of the
electrostatic ultrasonic transducer used in the ultrasonic speaker is in contact with the convex
portion of the plate-like fixing member, It fixes so that the peripheral part of an electrode may be
pressed down with a screw etc. by the said plate-shaped fixing member. As a result, the pair of
electrodes in the electrostatic ultrasonic transducer is configured such that the acoustic emission
surface is slightly convex, and as a result, a substantially uniform force is applied between the
pair of electrodes, and the vibrating film has a uniform force (distance). And stable membrane
vibration is obtained.
[0027]
Further, according to the directional acoustic system of the present invention, a carrier wave
signal of an ultrasonic frequency band is modulated by a signal of a first range of an audio signal
supplied from an acoustic source, and an electrostatic ultrasonic transducer is An ultrasonic
speaker driven to reproduce a signal sound in an audible frequency band; and a bass
reproduction speaker reproducing a signal in a second sound range lower than the first sound
range among audio signals supplied from the sound source. In the directional acoustic system,
the electrostatic ultrasonic transducer of the ultrasonic speaker includes: a first electrode having
a slit-like through hole; and a second electrode having a slit-like through hole A pair of electrodes
disposed such that the through hole of the first electrode and the through hole of the second
electrode form a pair, and including the first electrode and the second electrode Sandwiched And
a vibrating film to which a DC bias voltage is applied to the conductive layer, and the pair of
electrodes are electrode layers disposed in the longitudinal direction of the through hole inside
the through hole. A convex portion of a plate-like fixing member having a convex shape abuts on
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the vicinity of the central portion of the surface of the one of the pair of electrodes opposite to
the vibrating membrane. A modulation wave in which a plate-like fixing member and the pair of
electrodes are integrally fixed, and a carrier wave in an ultrasonic frequency band is modulated
by a signal wave in an audio frequency band between the electrode layers of the pair of
electrodes. Is applied. The directional acoustic system having the above configuration uses an
ultrasonic speaker including an electrostatic ultrasonic transducer having a slit-like through hole
in the electrode and an electrode layer facing the diaphragm inside the through hole. . Then,
among the audio signals supplied from the acoustic source, the ultrasonic speaker reproduces
the audio signal of the middle to high range (first range). Further, among the audio signals
supplied from the acoustic source, the audio signal in the low frequency range (second frequency
range) is reproduced by the bass reproduction speaker. Therefore, it is possible to reproduce the
sound in the middle to high frequency range so as to be emitted from a virtual sound source
formed in the vicinity of the sound wave reflection surface such as a screen with sufficient sound
pressure and wide band characteristics. In addition, since the low-range sound is directly output
from the low-range speaker in the sound system, the low-range sound can be enhanced, and a
more realistic sound environment can be created. Further, the back center of one of the pair of
electrodes sandwiching the diaphragm of the electrostatic ultrasonic transducer used in the
ultrasonic speaker is in contact with the convex portion of the plate-like fixing member, It fixes so
that the peripheral part of an electrode may be pressed down with a screw etc. by the said plateshaped fixing member.
As a result, the pair of electrodes in the electrostatic ultrasonic transducer is configured such that
the acoustic emission surface is slightly convex, and as a result, a substantially uniform force is
applied between the pair of electrodes, and the vibrating film has a uniform force (distance). And
stable membrane vibration is obtained.
[0028]
Hereinafter, embodiments of the present invention will be described in detail with reference to
the drawings. An example of the configuration of an electrostatic ultrasonic transducer according
to an embodiment of the present invention is shown in FIG. In the figure, reference numeral 1
denotes an electrostatic ultrasonic transducer, and the electrostatic ultrasonic transducer 1 has a
first electrode 10 having a through hole (not shown) and a second electrode having a through
hole (not shown). Of the first electrode 10, the through hole of the first electrode 10, and the
through hole of the second electrode 20, and the pair of electrodes comprising the first electrode
10 and the second electrode 20 And a conductive layer (not shown), and includes a vibrating film
30 to which a DC bias voltage is applied to the conductive layer.
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[0029]
The pair of electrodes 10 and 20 are formed of a conductive material, or have an electrode layer
facing the vibration film 30 inside the through hole, and any one of the pair of electrodes 10 and
20 is provided. Of the plate-like fixing member 25 having a convex shape (for example, a convex
curved surface) in the vicinity of the central portion of the surface of the electrode (in the present
embodiment, the second electrode 20) opposite to the vibrating film 30 The plate-shaped fixing
member 25 and the pair of electrodes 10 and 20 are integrally fixed by the screw 28 such that a
convex portion (for example, a convex curved surface) abuts. The plate-like fixing member 25 is
formed of a member having a rigidity equal to or higher than that of the pair of electrodes 10
and 20.
[0030]
With the above configuration, the back center of one of the pair of electrodes sandwiching the
diaphragm is in contact with the convex portion (for example, a convex curved surface) of the
plate-like fixing member 25, and the pair of electrodes 10 and 20 It fixes so that the peripheral
part of this may be pressed down with the screw 28 by the said plate-shaped fixing member 25.
As shown in FIG. As a result, the pair of electrodes 10 and 20 in the electrostatic ultrasonic
transducer 1 is configured such that the acoustic emission surface is slightly convex, and as a
result, a substantially uniform force is applied between the pair of electrodes 10 and 20. The
vibrating membrane 30 is held with uniform force (distance), and stable membrane vibration can
be obtained.
[0031]
When the electrostatic ultrasonic transducer 1 is driven, a DC bias voltage is applied to the
conductive layer of the vibrating film 30, and between the pair of electrodes 10 and 20 or
between the pair of electrodes 10 , 20, a modulated wave obtained by modulating a carrier wave
in the ultrasonic frequency band with a signal wave in the audible frequency band is applied.
[0032]
Next, another configuration of the electrostatic ultrasonic transducer according to the
embodiment of the present invention is shown in FIG.
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In the figure, the only difference from the electrostatic ultrasonic transducer shown in FIG. 1 in
the configuration is the shape of the plate-like fixing member, and the other configurations are
the same. In the electrostatic ultrasonic transducer 1 shown in FIG. 2, the plate-like fixing
member 26 is the vibrating film 30 of either one of the pair of electrodes 10 and 20 (the second
electrode 20 in the present embodiment). A projection 26A is provided at the central portion of
the surface of the plate-like fixing member 26 that abuts the opposite surface. 29 is a screw hole.
[0033]
With the above configuration, the back center of one of the pair of electrodes 10 and 20
sandwiching the diaphragm 30 abuts on the protrusion 26A formed at the central portion of the
plate-like fixing member 26, The peripheral portion 20 is fixed so as to be pressed down by the
screw 28 by the plate-like fixing member 26. As a result, the pair of electrodes in the electrostatic
ultrasonic transducer is configured such that the acoustic emission surface is a light convex
surface, and as a result, a substantially uniform force is applied between the pair of electrodes 10
and 20, and the diaphragm 30 is uniform. It is possible to obtain stable membrane vibration by
holding it with a constant force (distance). In the examples shown in FIGS. 1 and 2, the first
electrode 10, the second electrode, and the plate-like fixing member (25 or 26) are integrally
fixed by screws, but the present invention is limited thereto. Alternatively, they may be fixed by
an adhesive or the like.
[0034]
In addition, the plate-like fixing member which applies stress to the first electrode 10 and the
second electrode so that the acoustic radiation surface is convex and fixes them integrally is
limited to the shape shown in FIG. 1 and FIG. Alternatively, for example, as shown in FIG. 3, a
plate-like fixing member may be provided having a band-like protrusion 27A having a
semicircular cross section at the center. The first electrode 10 and the second electrode 20 of the
electrostatic ultrasonic transducer 1 are integrally fixed with the plate-like fixing member shown
in FIG. 3 instead of the plate-like fixing member shown in FIGS. Even in this case, the same effect
as obtained by the configuration of FIGS. 1 and 2 can be obtained. In addition, 29 is a screw hole.
04-05-2019
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[0035]
The fixing structure of the electrostatic ultrasonic transducer according to the present
embodiment shown in FIGS. 1 to 3 described above can be all applied if already described, and
the electrostatic ultrasonic transducer of FIG. Also applies to The configuration and operation of
the electrostatic ultrasonic transducer have already been described for the electrostatic
ultrasonic transducer in FIG. 13, so the description will be omitted here. The electrostatic
ultrasonic transducer in FIGS. 1 to 3 conceptually shows a push-pull type electrostatic ultrasonic
transducer.
[0036]
Next, a specific configuration example of an electrostatic ultrasonic transducer to which the
present invention (a structure in which a pair of electrodes are integrally fixed by a plate-like
fixing member as shown in FIGS. 1 to 3) is applied is shown in FIG. Shown in. However, the state
fixed by the plate-like reinforcing member is omitted. FIG. 4A is a cross-sectional view, and FIG.
4B is a plan view of the electrode viewed from the vibrating film side.
[0037]
The electrostatic ultrasonic transducer 1 to which the present invention is applied includes a
vibrating membrane 30 and a front side electrode (first electrode) 10 and a back side electrode
(second electrode) 20 which are a pair of electrodes for holding the vibrating membrane 30. And
the circuit that drives it.
[0038]
The front side electrode 10 has a vibrating membrane support portion 11 for holding the
vibrating membrane 30, an opening 13 which is a slit-like (rectangular) through hole, and the
through hole inside the opening (through hole) 13. And a bridge portion 12 disposed parallel to
the longitudinal direction.
The bridge portion 12 is arranged such that its bottom surface (the diaphragm facing surface
facing the diaphragm 30) maintains a predetermined distance (for example, 5 to 6 ?m) with the
surface of the diaphragm 30 when not vibrating. Ru. Further, an electrode layer 14 is formed on
04-05-2019
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the diaphragm facing surface facing the diaphragm 30 of the bridge portion 12.
[0039]
Similarly, the back side electrode 20 includes a vibrating membrane support 21 for holding the
vibrating membrane 30, an opening 23 which is a slit-like (rectangular) through hole, and an
opening 23 (through hole) In the inside, it is formed of a bridge portion 22 disposed parallel to
the longitudinal direction of the through hole. The bridge portion 22 is arranged such that its
bottom surface (the vibrating film facing surface facing the vibrating film 30) holds a
predetermined distance (for example, 5 to 6 ?m) with the film surface of the vibrating film 30
when not vibrating. Ru. Also, an electrode layer 24 is formed on the diaphragm facing surface
facing the diaphragm 30 of the bridge portion 22.
[0040]
The thickness of the front side electrode 10 and the back side electrode 20 is, for example, about
1.5 mm. Further, as shown in FIG. 4B, the width of the slit-like through hole is, for example, about
1.5 mm, and the width of the bridge portion is about 0.5 mm.
[0041]
The front side electrode 10 and the rear side electrode 20 are formed of a nonconductive base
material (various plastics, glass, ceramics, etc.), and plated and printed with metal (gold, silver,
copper, aluminum etc.) as the electrode layers 14, 24. , Vapor deposition, paste, etc. An AC
voltage of about 10 to 300 V is applied to the electrode layers 14 and 24 by AC signals 37A and
37B on the circuit side.
[0042]
The vibrating film 30 is formed by covering the vibrating electrode (conductive layer) 32 with
the dielectric films (insulators) 31 and 32. For example, a metallized one side of a polymer film
(dielectric film) having a thickness of several microns is laminated with an adhesive. As a material
of the polymer film, for example, poly ethylene terephthalate (PET), aramid, poly ester, poly
04-05-2019
17
ethylene naphthalate (PEN), poly phenylene sulfide (PPS) or the like is used. The material of the
metallized portion forming the vibrating electrode 32 is most commonly Al (aluminum), and may
be Ni, Cu, SUS, Ti or the like. The thickness of the metallized portion is preferably about 100 ┼ to
1,500 ┼. A DC bias voltage of 10 to 300 V is applied to the metallized portion (the vibrating
electrode 32) of the vibrating membrane from the DC power supply 36 on the circuit side.
[0043]
The operation of the electrostatic ultrasonic transducer 1 of the above configuration is basically
the same as that of the electrostatic ultrasonic transducer 3 shown in FIG. 13, and an acoustic
signal is generated by the push-pull operation of the vibrating membrane 30. Do. That is, in the
electrostatic ultrasonic transducer 1, the pair of electrodes 10, 20 have the same number and
plural slit-like openings (through holes) 13, 23 at the positions facing each other through the
vibrating film 30. Between the electrode layers 14 and 24 of the bridge portions 12 and 22 of
the pair of electrodes 10 and 20, alternating current signals 37A and 37B which are mutually
phase-inverted by the signal source 37 are applied. Capacitors are formed between the electrode
layer 14 and the vibrating electrode 32, and between the electrode layer 24 and the vibrating
electrode 32, respectively. Further, a DC bias voltage of a single polarity (positive in this
embodiment) is applied to the vibrating electrode 32 of the vibrating membrane 30 by the DC
power supply 36.
[0044]
As a result, in the positive half cycle of the alternating current signal 37A output from the signal
source 37, a positive voltage is applied to the electrode layer 14 of the bridge portion 12 of the
front side electrode 10. The electrostatic repulsion force acts on the surface portion 15A which is
not sandwiched by 20, and the surface portion 15A is pulled downward in FIG. At this time, the
alternating current signal 37B has a negative cycle, and a negative voltage is applied to the
electrode layer 24 of the bridge portion 22 of the opposing back side electrode 20, so that the
surface portion 15A of the diaphragm 30 is The electrostatic attraction force acts on the back
surface portion 15B which is the back surface side, and the back surface portion 15B is pulled
further downward in FIG.
[0045]
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18
Therefore, the film portion of the vibrating film 30 which is not held by the pair of electrodes 10
and 20 receives electrostatic attraction force and electrostatic repulsion force (electrostatic
repulsive force) in the same direction. Similarly, for the negative half cycle of the alternating
current signal output from the signal source 37, the surface portion 15A of the vibrating
membrane 30 in FIG. In FIG. 4, electrostatic repulsive force acts on the upper side, and a film
portion of the vibrating film 30 which is not sandwiched by the pair of electrodes 10 and 20
receives electrostatic attractive force and electrostatic repulsive force in the same direction. In
this manner, the vibrating film 30 receives the electrostatic attraction force and the electrostatic
repulsion force in the same direction according to the change of the polarity of the alternating
current signal, and the direction in which the electrostatic force acts alternately changes. That is,
acoustic signals at sound pressure levels sufficient to obtain a parametric array effect can be
generated. The acoustic signal emitted from the vibrating film 30 is emitted to the outside as a
plane wave through the slit-like openings 13 and 23.
[0046]
FIG. 5 is a view showing a modification of the electrostatic ultrasonic transducer to which the
present invention is applied. FIGS. 5A, 5B, and 5C are plan views of the front side electrode as
viewed from the vibrating film side. In addition, a back side electrode also becomes the same
structure.
[0047]
The front side electrode 10 shown in FIG. 5A is the same as the front side electrode 10 shown in
FIG. 4B, and is the most basic configuration example of the electrostatic ultrasonic transducer to
which the present invention is applied. is there.
[0048]
The front side electrode 40 shown in FIG. 5 (B) has a reinforcing member 41 for reinforcing a
base material (for example, plastic etc.) forming the electrode, in the central portion of the slitlike through hole in the longitudinal direction. An example is shown in which it is added in the
direction orthogonal to the longitudinal direction of.
In this example, an example is shown in which the electrode layer facing the diaphragm is
divided into two by the reinforcing member 41 into the electrode layer 42A and the electrode
04-05-2019
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layer 42B. However, the length of the reinforcing member 41 (the depth of the through hole is
The length in the direction is made the same as the length of the bridge (the length in the depth
direction of the through hole), and the surface of the bridge (the surface facing the diaphragm)
and the surface of the reinforcing member 41 are aligned. Can also be formed as a continuous
surface.
[0049]
Further, the front side electrode 50 shown in FIG. 5C has two reinforcing members 51 and 52 for
reinforcing a base material (for example, plastic etc.) forming the electrode, and a slit-like
through hole is even. An example is shown in which the length is added. In this example, an
example is shown in which the electrode layer facing the diaphragm is divided into three into the
electrode layer 53A, the electrode layer 53B, and the electrode layer 53C by the reinforcing
members 51 and 52. The length of the through hole (the depth direction of the through hole) is
the same as the length of the bridge (the length of the through hole in the depth direction), and
the surface of the bridge (the surface facing the diaphragm) and the reinforcing member The
electrode layer can also be formed as a continuous surface by combining the surfaces 51 and 52.
[0050]
As described above, when the transducer area is small, a slit-like rectangular hole (through hole)
as shown in FIG. 5A may be formed, but the transducer area is increased and the mechanical
strength of the electrode is secured. If necessary, as shown in FIGS. 2B and 2C, the base material
is reinforced in the direction perpendicular to the longitudinal direction of the through hole at
the middle of the slit. This makes it possible to increase the strength of the electrode of the
electrostatic ultrasonic transducer, and makes it possible to manufacture an electrostatic
ultrasonic transducer with a large area (for example, 50 mm О 50 mm or more).
[0051]
The structure of the electrostatic ultrasonic transducer to which the present invention is applied
has been described above. The feature of an example of the electrostatic ultrasonic transducer to
which the present invention shown in FIG. 4 is applied is shown in FIG. As shown in (B) and (C), it
is necessary to open a through hole (opening) in a rectangular shape (slit shape) in a pair of
04-05-2019
20
electrodes, and it is particularly important that the electrode is placed against the center of the
rectangular diaphragm. In order to form a layer, a base material (bridge portion) for forming an
electrode pattern in a bridge shape is to be left. This results from expanding the bridge structure
for round holes shown in FIG. 7 into rectangular holes.
[0052]
Here, the configuration of an electrostatic ultrasonic transducer in which an electrode layer
having a bridge structure is provided in a circular through hole shown in FIG. 7 will be described.
FIG. 7A is a plan view of the pair of electrodes 70 sandwiching the diaphragm, one of the
electrodes 70A viewed from the diaphragm side. FIG. 7B is a cross-sectional view of the
electrostatic ultrasonic transducer, and is a cross-sectional view in the XX ? direction in FIG. 7A.
[0053]
In this electrostatic ultrasonic transducer, a circular through hole 71 is provided in an electrode
(base material) 70 formed of a nonconductive material, and a cruciform bridge portion 72 facing
the diaphragm 30 in the circular through hole 71 is provided. Is provided. The cross bridge
portion 72 is formed such that its length (the length in the depth direction of the through hole)
has a predetermined distance (for example, 5 to 6 ?m) from the surface of the vibrating
membrane 30 when it is not vibrating. An electrode layer 73 is formed on the surface of the
cross bridge 72 facing the vibrating membrane 30. Similarly, a through hole 71A, a cross bridge
portion 72A, and an electrode layer 73A are formed in the other electrode 70A. Then, a direct
current bias voltage is applied to the vibrating electrode 32 of the vibrating film 30, and an
alternating current signal is applied between the cross-shaped electrode layer 73 and the
electrode layer 73A.
[0054]
Such a structure makes it possible to efficiently convert electrical energy into film vibration
energy (to obtain an acoustic signal with a large amplitude).
[0055]
The structure shown in FIG. 7 is such that the electrode layer is formed in a cross bridge shape
04-05-2019
21
with respect to a round hole (for example, ? 0.75 mm), but the aperture ratio (the area ratio of
acoustic energy radiation) is 15% or less .
On the other hand, when an electrode layer of a bridge structure is applied to a rectangular
through hole as in the electrostatic ultrasonic transducer of the present invention, the vibration
area of the diaphragm can be approximately tripled, and An aperture ratio of 3 times (45%) can
be obtained. The meaning of this number is that the rectangular bridge structure of the present
invention is capable of emitting three times as much acoustic energy when the membrane
amplitude of both the round hole and the rectangular hole is the same. is there.
[0056]
Further, in the electrodes 10 and 20 of the electrostatic ultrasonic transducer of the present
invention shown in FIG. 4, the configuration of the bridge portion in the through hole is simple as
compared with the electrode 70 of the electrostatic ultrasonic transducer shown in FIG. This
makes it easy to manufacture the electrode.
[0057]
Furthermore, in order to further increase the electrostatic force, it is also effective to form the
vibrating film 30A in a laminated structure of three or more layers.
That is, as in the case of the electrostatic ultrasonic transducer 2 shown in FIG. 6, the
electrostatic force is formed by laminating the two vibration electrodes 32, 34 and the dielectric
films 31, 33, 35 to form the vibration film 30A. To increase the membrane amplitude.
[0058]
As described above, in the electrostatic ultrasonic transducer according to the present invention,
the vibration area of the vibrating film is increased by making the vibrating shape of the
vibrating film into a rectangular shape (slit shape), and the opening for emitting an acoustic
signal. Increase the area of Therefore, a large amplitude acoustic signal can be obtained with a
low voltage signal. As a result, the electrical / acoustic energy conversion efficiency can be
improved to obtain an acoustic signal with high sound pressure.
04-05-2019
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[0059]
In addition, an electrostatic ultrasonic transducer to which the present invention is applied
includes a first electrode having a slit-like through hole, a second electrode having a slit-like
through hole, and the first electrode. A through hole and the through hole of the second
electrode are arranged to form a pair, and are sandwiched by a pair of electrodes consisting of
the first electrode and the second electrode, and have a conductive layer. A vibrating membrane
to which a DC bias voltage is applied to the conductive layer, the pair of electrodes including an
electrode layer disposed in the longitudinal direction of the through hole inside the through hole,
the pair of electrodes The convex portion of the plate-like fixing member having a convex shape
is brought into contact with the vicinity of the central portion of the surface on the opposite side
to the vibrating film of any one of the electrodes, and the plate-like fixing member The pair of
electrodes is integrally fixed to the pair of electrodes. The kicking the electrode layers modulated
wave obtained by modulating the carrier wave in the ultrasonic frequency band by signal waves
in the audio frequency band is applied.
[0060]
With the above configuration, the back center of one of the pair of electrodes sandwiching the
diaphragm is in contact with the convex portion of the plate-like fixing member, and the
peripheral portion of the pair of electrodes is screwed by the plate-like fixing member. It is fixed
so that it can be pressed down by.
As a result, the pair of electrodes in the electrostatic ultrasonic transducer is configured such that
the acoustic emission surface is slightly convex, and as a result, a substantially uniform force is
applied between the pair of electrodes, and the vibrating film has a uniform force (distance). And
stable membrane vibration is obtained.
[0061]
Further, in the electrostatic ultrasonic transducer according to the present invention, the platelike fixing member is a member of the plate-like fixing member which is in contact with the
surface of either one of the pair of electrodes opposite to the vibrating membrane. The surface is
formed as a convex curved surface. With the above configuration, the back center of one of the
pair of electrodes sandwiching the diaphragm contacts the convex surface of the plate-like fixing
member, and the peripheral portion of the pair of electrodes is screwed by the plate-like fixing
04-05-2019
23
member. It is fixed so as to be held down. As a result, the pair of electrodes in the electrostatic
ultrasonic transducer is configured such that the acoustic emission surface is slightly convex, and
as a result, a substantially uniform force is applied between the pair of electrodes, and the
vibrating film has a uniform force (distance). And stable membrane vibration is obtained.
[0062]
Further, in the electrostatic ultrasonic transducer according to the present invention, the platelike fixing member is a member of the plate-like fixing member which is in contact with the
surface of either one of the pair of electrodes opposite to the vibrating membrane. It has a
protrusion at the center of the surface. With the above configuration, the back center of one of
the pair of electrodes sandwiching the diaphragm contacts the protrusion formed at the center of
the plate-like fixing member, and the peripheral portion of the pair of plates is the plate-like. It is
fixed so that it can be pressed down by a screw etc. by a fixing member. As a result, the pair of
electrodes in the electrostatic ultrasonic transducer is configured such that the acoustic emission
surface is slightly convex, and as a result, a substantially uniform force is applied between the
pair of electrodes, and the vibrating film has a uniform force (distance ) And stable membrane
vibration can be obtained.
[0063]
Next, a configuration example of an ultrasonic speaker using an electrostatic ultrasonic
transducer to which the present invention is applied is shown in FIG. The ultrasonic speaker
according to the present embodiment has the above-described electrostatic ultrasonic transducer
of the present invention (FIG. 4), that is, a slit-like through hole (opening), and an electrode at the
bridge in the through hole. It is composed of a Push-Pull type electrostatic ultrasonic transducer
provided with a layer. This electrostatic ultrasonic transducer is a plate-like fixing member shown
in FIGS. 1 to 3, and a pair of electrodes are integrally fixed so that the acoustic radiation surface
has a convex shape. The figure does not show this condition for the sake of convenience.
[0064]
In FIG. 8, the ultrasonic speaker according to this embodiment includes an audio frequency wave
oscillation source 201 that generates a signal wave in an audio wave frequency band, and a
carrier wave oscillation that generates and outputs a carrier wave in an ultrasonic frequency
04-05-2019
24
band. A source 202, a modulator 203, a power amplifier 204, and an electrostatic ultrasonic
transducer 205 are included. The modulator 203 modulates the carrier wave output from the
carrier wave oscillation source 202 with the signal wave in the audio wave frequency band
output from the audio frequency wave oscillation source 201, and the electrostatic ultrasonic
wave is transmitted through the power amplifier 204. The transducer 205 is supplied.
[0065]
In the above configuration, the carrier wave in the ultrasonic frequency band output from the
carrier wave oscillation source 202 is modulated by the modulator 203 by the signal wave
output from the audio frequency wave oscillation source 201, and the modulation signal
amplified by the power amplifier 204. The electrostatic ultrasonic transducer 205 is driven. As a
result, the modulated signal is converted into a sound wave of a finite amplitude level by the
electrostatic ultrasonic transducer 205, and this sound wave is emitted into the medium (in air)
and the original audible can be heard by the nonlinear effect of the medium (air). Signal sound in
the frequency band is self-reproduced.
[0066]
That is, since the sound wave is a compression wave propagating through the air as a medium, in
the process of propagating the modulated ultrasonic wave, the dense part and the sparse part of
the air appear prominently, and the sound speed is high at the dense part. Since the sound
velocity of the sparse part is slowed, distortion occurs in the modulated wave itself, and as a
result, the waveform is separated into the carrier wave (ultrasonic frequency band), and the
signal wave (sound signal) in the audible wave frequency band is reproduced.
[0067]
As the electrostatic ultrasonic transducer 205, the electrostatic ultrasonic transducer 1 of the
present invention shown in FIG. 4 is used, and an acoustic signal of high sound pressure can be
outputted with a wide band.
Therefore, it can be used as a speaker for various applications.
[0068]
04-05-2019
25
Ultrasonic waves are highly attenuated in the air and decay in proportion to the square of their
frequency. Therefore, when the carrier frequency (ultrasound) is low, it is possible to provide an
ultrasonic speaker that can transmit sound in the form of a beam with less attenuation.
Conversely, if the carrier frequency is high, the attenuation is so severe that the parametric array
effect does not occur sufficiently, and it is possible to provide an ultrasonic speaker in which the
sound spreads. These are very effective functions because they can be used with the same
ultrasonic speaker depending on the application.
[0069]
Further, since the electrostatic ultrasonic transducer 1 of the present invention shown in FIG. 4 is
used for this ultrasonic speaker, one of the pair of electrodes sandwiching the vibrating film of
the electrostatic ultrasonic transducer is used. The central portion of the back face is in contact
with the convex portion of the plate-like fixing member, and the peripheral portions of the pair of
electrodes are fixed so as to be pressed down by the screw or the like by the plate-like fixing
member. As a result, the pair of electrodes in the electrostatic ultrasonic transducer is configured
such that the acoustic emission surface is slightly convex, and as a result, a substantially uniform
force is applied between the pair of electrodes, and the vibrating film has a uniform force
(distance ), And stable membrane vibration is obtained.
[0070]
Next, the electrostatic ultrasonic transducer according to the present invention, that is, having a
slit-like through hole (opening), having an electrode layer at the bridge in the through hole, and
having a pair of electrodes by a plate-like fixing member A directional acoustic system using an
ultrasonic speaker composed of a physically fixed Push-Pull type electrostatic ultrasonic
transducer (FIG. 4) will be described. The electrostatic ultrasonic transducer is hereinafter also
simply referred to as "ultrasonic transducer".
[0071]
Hereinafter, a projector (display device) will be described as an example of the directional
acoustic system according to the present invention. FIG. 9 shows the use of the projector
04-05-2019
26
according to the present invention. As shown in the figure, the projector 301 is installed behind
the viewer 303 and projects an image on the screen 302 installed in front of the viewer 303, and
the screen 302 by the ultrasonic speaker mounted on the projector 301. The virtual sound
source is formed on the projection plane of the to reproduce the sound.
[0072]
The external configuration of the projector 301 is shown in FIG. The projector 301 includes a
projector main body 320 including a projection optical system for projecting an image on a
projection surface such as a screen, and ultrasonic transducers 324A and 324B capable of
emitting sound waves in an ultrasonic frequency band, and includes an acoustic source An
ultrasonic speaker that reproduces a sound signal of an audible frequency band from a supplied
audio signal is integrally configured. In the present embodiment, in order to reproduce a stereo
sound signal, ultrasonic transducers 324A and 324B constituting ultrasonic speakers on the left
and right sides of the projector lens 331 constituting the projection optical system are mounted
on the projector main body. . Furthermore, on the bottom surface of the projector main body
320, a bass reproduction speaker 323 is provided. Further, reference numeral 325 denotes a
height adjustment screw for adjusting the height of the projector main body 320, and reference
numeral 326 denotes an exhaust port for an air cooling fan.
[0073]
Further, in the projector 301, as an ultrasonic transducer constituting an ultrasonic speaker, a
Push-Pull type electrostatic ultrasonic transducer according to the present invention (a slit-like
through hole and an electrode layer formed in a bridge portion in the through hole). It is possible
to use a high-sound pressure oscillation of a wide frequency band acoustic signal (sound wave in
the ultrasonic frequency band). Therefore, by changing the frequency of the carrier wave to
control the spatial reproduction range of the reproduction signal in the audio frequency band,
the acoustic effect that can be obtained by the stereo surround system, 5.1ch surround system,
etc. It is possible to realize a projector that can be realized without the need for a large-scale
acoustic system and that is easy to carry.
[0074]
Next, the electrical configuration of the projector 301 is shown in FIG. The projector 301
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includes an operation input unit 310, a reproduction range setting unit 312, a reproduction
range control processing unit 313, an audio / video signal reproduction unit 314, a carrier wave
oscillation source 316, modulators 318A and 318B, and power amplifiers 322A and 322B. And
an ultrasonic speaker consisting of electrostatic ultrasonic transducers 324A and 324B, high
pass filters 317A and 317B, low pass filter 319, a mixer 321, a power amplifier 322C, a speaker
for reproducing a low frequency sound, a projector main body And 320. The ultrasonic
transducers 324A and 324B are push-pull type electrostatic ultrasonic transducers according to
the present invention (electrostatic ultrasonic waves having slit-like through holes and having an
electrode layer formed in a bridge portion in the through holes). Transducers).
[0075]
The projector body 320 has an image generation unit 332 that generates an image, and a
projection optical system 333 that projects the generated image on a projection surface. The
projector 301 is configured by integrating an ultrasonic speaker and bass reproduction speaker
323 and a projector main body 320.
[0076]
The operation input unit 310 has various function keys including a ten-key pad, numeric keys,
and a power key for turning the power on and off. The reproduction range setting unit 312 is
configured such that the user can input data specifying the reproduction range of the
reproduction signal (signal sound) by key operation of the operation input unit 310, and when
the data is input The frequency of the carrier wave that defines the reproduction range of the
reproduction signal is set and held. The setting of the reproduction range of the reproduction
signal is performed by designating the distance that the reproduction signal reaches in the
radiation axis direction from the sound wave emission surface of the ultrasonic transducers
324A, 324B.
[0077]
Also, the reproduction range setting unit 312 can set the frequency of the carrier wave by the
control signal output from the audio / video signal reproduction unit 314 according to the
contents of the video. Further, the reproduction range control processing unit 313 refers to the
setting contents of the reproduction range setting unit 312, and changes the frequency of the
04-05-2019
28
carrier wave generated by the carrier wave oscillation source 316 so as to become the set
reproduction range. It has a function of controlling the oscillation source 316. For example, when
the distance corresponding to the carrier wave frequency of 50 kHz is set as internal information
of the reproduction range setting unit 312, the carrier wave oscillation source 316 is controlled
to oscillate at 50 kHz.
[0078]
The reproduction range control processing unit 313 stores in advance a table indicating the
relationship between the distance at which the reproduction signal reaches in the radiation axis
direction from the sound wave emitting surfaces of the ultrasonic transducers 324A and 324B
defining the reproduction range and the frequency of the carrier wave. Storage unit. The data in
this table can be obtained by actually measuring the relationship between the carrier wave
frequency and the arrival distance of the reproduction signal. The reproduction range control
processing unit 313 obtains the frequency of the carrier wave corresponding to the distance
information set with reference to the table based on the setting content of the reproduction
range setting unit 312, and the carrier wave frequency becomes the carrier frequency. The wave
oscillation source 316 is controlled.
[0079]
The audio / video signal reproduction unit 314 is, for example, a DVD player using a DVD as a
video medium, and among the reproduced audio signals, the R channel audio signal is
transmitted to the modulator 318A via the high pass filter 317A. The audio signal is output to
the modulator 318 B via the high pass filter 317 B, and the video signal is output to the video
generation unit 332 of the projector main body 320. Also, the R channel audio signal and L
channel audio signal output from the audio / video signal reproduction unit 314 are synthesized
by the mixer 321 and input to the power amplifier 322 C via the low pass filter 319. There is.
The audio / video signal reproduction unit 314 corresponds to an audio source.
[0080]
The high pass filters 317A and 317B have a characteristic of passing only the frequency
component of middle to high range (first range) in the voice signal of R channel and L channel
respectively, and the low pass filter is R channel, It has the characteristic of passing only the
04-05-2019
29
frequency component of the low frequency band (second frequency band) in the audio signal of L
channel. Therefore, among the audio signals of the R channel and L channel, the audio signals in
the middle to high range are reproduced by the ultrasonic transducers 324A and 324B,
respectively, and the audio signals of the low frequency range of the audio signals of the R
channel and L channel are reproduced. It will be reproduced by the bass reproduction speaker
323.
[0081]
The audio / video signal reproduction unit 314 is not limited to a DVD player, and may be a
reproduction device that reproduces a video signal input from the outside. In addition, the audio
/ video signal reproduction unit 314 causes the reproduction range setting unit 312 to change
the reproduction range so as to dynamically change the reproduction range of the reproduction
sound to produce an acoustic effect according to the scene of the image to be reproduced. It has
a function to output a control signal to instruct.
[0082]
The carrier wave oscillation source 316 has a function of generating a carrier wave of the
frequency of the ultrasonic frequency band instructed by the reproduction range setting unit 312
and outputting the carrier wave to the modulators 318A and 318B. Modulators 318A and 318B
AM modulate the carrier wave supplied from the carrier wave oscillation source 316 with an
audio signal in the audio frequency band output from the audio / video signal reproduction unit
314, and respectively modulate the modulated signal with a power amplifier. It has a function to
output to 322A, 322B.
[0083]
The ultrasonic transducers 324A and 324B are driven by modulation signals output from the
modulators 318A and 318B via the power amplifiers 322A and 322B, respectively, convert the
modulation signals into sound waves of a finite amplitude level and It has a function to emit and
reproduce the signal sound of the audio frequency band (reproduction signal).
[0084]
04-05-2019
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The video generation unit 332 has a display such as a liquid crystal display or a plasma display
panel (PDP), and a drive circuit that drives the display based on the video signal output from the
audio / video signal reproduction unit 314. An image obtained from the video signal output from
the audio / video signal reproduction unit 314 is generated.
The projection optical system 333 has a function of projecting an image displayed on a display
on a projection surface such as a screen installed in front of the projector main body 320.
[0085]
Next, the operation of the projector 301 configured as described above will be described. First,
data (distance information) instructing the reproduction range of the reproduction signal from
the operation input unit 310 is set in the reproduction range setting unit 312 by the user's key
operation, and the audio / video signal reproduction unit 314 is instructed to reproduce.
[0086]
As a result, distance information defining the reproduction range is set in the reproduction range
setting unit 312, and the reproduction range control processing unit 313 takes in the distance
information set in the reproduction range setting unit 312 and stores the information in the
built-in storage unit. The frequency of the carrier wave corresponding to the set distance
information is determined with reference to the table, and the carrier wave oscillation source 316
is controlled to generate the carrier wave of the frequency. As a result, the carrier wave
oscillation source 316 generates a carrier wave of a frequency corresponding to the distance
information set in the reproduction range setting unit 312, and outputs the carrier wave to the
modulators 318A and 318B.
[0087]
On the other hand, the audio / video signal reproduction unit 314 modulates the R channel audio
signal among the reproduced audio signals to the modulator 318A via the high pass filter 317A
and the L channel audio signal to the high pass filter 317B. The audio signal of the R channel and
the audio signal of the L channel are output to the mixer 321 at 318 B, and the video signal is
output to the video generation unit 332 of the projector main body 320.
04-05-2019
31
[0088]
Therefore, the high-pass filter 317A inputs the voice signal of middle to high range among the
voice signals of the R channel to the modulator 318, and the high-pass filter 317B sets the voice
signal of middle to high range among the voice signals of the L channel on the modulator 318B.
Is input to
The audio signal of the R channel and the audio signal of the L channel are synthesized by the
mixer 321, and the audio signal of the bass region among the audio signal of the R channel and
the audio signal of the L channel is input to the power amplifier 322C by the low pass filter 319.
Be done.
[0089]
The video generation unit 332 drives the display based on the input video signal to generate and
display a video. The image displayed on this display is projected by the projection optical system
333 onto a projection plane, for example, the screen 302 shown in FIG. Modulator 318A, on the
other hand, AM modulates the carrier wave output from carrier wave oscillation source 316 with
the voice signal in the middle to high frequency range of the R channel voice signal output from
high pass filter 317A, and outputs it to power amplifier 322A. Do. Further, modulator 318B AM
modulates the carrier wave output from carrier wave oscillation source 316 with the voice signal
in the middle to high range of the L channel voice signal output from high pass filter 317B, and
outputs the result to power amplifier 322B. Do.
[0090]
The modulation signals amplified by the power amplifiers 322A and 322B are applied between
the electrode layer 14 of the front side electrode 10 of the ultrasonic transducers 324A and
324B and the electrode layer 24 of the back side electrode 20 (see FIG. 4). The modulated signal
is converted to a sound wave (acoustic signal) of a finite amplitude level and emitted to a medium
(in air), and from the ultrasonic transducer 324A, the mid-to-high range audio signal in the
above-mentioned R channel audio signal Is reproduced, and from the ultrasonic transducer 324B,
the sound signal of the middle to high range in the sound signal of the L channel is reproduced.
Also, the audio signal of the bass range in the R channel and L channel amplified by the power
amplifier 322 C is reproduced by the bass reproduction speaker 323.
04-05-2019
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[0091]
As described above, in the propagation of the ultrasonic wave radiated into the medium (in air)
by the ultrasonic transducer, the speed of sound becomes high in the high sound pressure area
along with the propagation, and the speed of sound is slow in the low sound pressure area.
Become. As a result, waveform distortion occurs.
[0092]
If the signal in the ultrasonic band (carrier wave) to be emitted is modulated (AM modulated)
with the signal in the audio frequency band, the signal wave in the audio frequency band used at
the time of modulation is It is formed to be separated from the carrier wave in the sound wave
frequency band and to be self-demodulated. At this time, the spread of the reproduction signal
becomes a beam due to the characteristics of the ultrasonic wave, and the sound is reproduced
only in a specific direction which is completely different from that of a normal speaker.
[0093]
The beam-like reproduction signal output from the ultrasonic transducer 324 constituting the
ultrasonic speaker is emitted by the projection optical system 333 toward the projection surface
(screen) on which the image is projected, and is reflected and diffused by the projection surface .
In this case, the reproduction signal is separated from the carrier wave in the radiation axis
direction (normal direction) from the sound wave emission surface of the ultrasonic transducer
324 according to the frequency of the carrier wave set in the reproduction range setting unit
312. The reproduction range changes because the distance to the target and the beam width of
the carrier wave (beam divergence angle) are different.
[0094]
A state at the time of reproduction of a reproduction signal by an ultrasonic speaker configured
to include the ultrasonic transducers 324A and 324B in the projector 301 is shown in FIG. When
the ultrasonic transducer is driven by the modulation signal in which the carrier wave is
04-05-2019
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modulated by the audio signal in the projector 301, if the carrier frequency set by the
reproduction range setting unit 312 is low, the ultrasonic transducer is generated. The distance
from the sound wave emitting surface 324 to the direction of the radiation axis (the distance
from the carrier wave to the separation of the reproduction signal in the normal line direction of
the sound wave emitting surface, ie, the distance to the reproduction point increases.
[0095]
Therefore, the beam of the reproduced signal of the reproduced audio frequency band reaches
the projection surface (screen) 302 without being relatively spread, and is reflected at the
projection surface 302 in this state, so that the reproduction range is as shown in FIG. In this
case, the audible range A indicated by the dotted arrow is obtained, and the reproduced signal
(reproduced sound) can be heard only in a relatively far and narrow range from the projection
plane 302.
[0096]
On the other hand, when the carrier frequency set by the reproduction range setting unit 312 is
higher than that described above, the sound wave emitted from the sound wave emitting surface
of the ultrasonic transducer 324 is narrowed compared to the case where the carrier frequency
is low. However, the distance from the acoustic wave emitting surface of the ultrasonic
transducer 324 to the separation of the reproduction signal from the carrier wave in the
radiation axis direction (normal direction of the acoustic wave emitting surface), ie, the distance
to the reproduction point becomes short.
[0097]
Therefore, the beam of the reproduced signal in the audible frequency band is expanded before
reaching the projection surface 302 to reach the projection surface 302, and is reflected at the
projection surface 302 in this state, so that the reproduction range is as shown in FIG. An audible
range B indicated by a solid arrow at 9 is obtained, and the reproduced signal (reproduced
sound) can be heard only in a relatively close and wide range from the projection plane 302.
[0098]
As described above, in the projector according to the present invention, a Push-Pull type
electrostatic ultrasonic transducer (having slit-like through holes, having an electrode layer in the
bridge portion in the through holes, and having a pair of electrodes An ultrasonic speaker
composed of an electrostatic ultrasonic transducer (which is integrally fixed by a plate-like fixing
04-05-2019
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member so that the acoustic emission surface is convex) is used. Sound pressure level and
broadband characteristics can be reproduced so as to be emitted from a virtual sound source
formed in the vicinity of a sound wave reflection surface such as a screen.
This makes it easy to control the reproduction range.
In the projector according to the present invention, the back center of one of the pair of
electrodes sandwiching the diaphragm of the electrostatic ultrasonic transducer used for the
ultrasonic speaker is a convex portion of the plate-like fixing member. It abuts, and the
peripheral portions of the pair of electrodes are fixed by the plate-like fixing member so as to be
pressed by a screw or the like.
As a result, the pair of electrodes in the electrostatic ultrasonic transducer is configured such that
the acoustic emission surface is slightly convex, and as a result, a substantially uniform force is
applied between the pair of electrodes, and the vibrating film has a uniform force (distance And
stable membrane vibration can be obtained.
[0099]
The above-mentioned projector is used to view an image on a large screen, but recently, a largescreen liquid crystal television and a large-screen plasma television have rapidly become
widespread, and these large-screen televisions are also widely used. The ultrasonic speaker of the
present invention can be effectively used.
[0100]
That is, by using the ultrasonic speaker according to the present invention for a large screen
television, it becomes possible to locally emit an audio signal toward the front of the large screen
television.
[0101]
The embodiment of the present invention has been described above, but the electrostatic
ultrasonic transducer, the ultrasonic speaker, and the display device of the present invention are
not limited to the above illustrated examples, and the present invention is not limited thereto. Of
course, various changes can be made without departing from the scope of the invention.
04-05-2019
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[0102]
FIG. 1 is a view showing a configuration example of an electrostatic ultrasonic transducer
according to an embodiment of the present invention.
FIG. 6 is a view showing another configuration example of the electrostatic ultrasonic transducer
according to the embodiment of the present invention.
The figure which shows the other structural example of the plate-shaped fixing member used for
the electrostatic ultrasonic transducer which concerns on embodiment of this invention.
The figure which shows the structural example of the electrostatic-type ultrasonic transducer to
which this invention is applied. The figure which this invention shows the other structural
example of an electrostatic-type ultrasonic transducer. The figure which shows the example
which made the vibrating electrode of the vibrating membrane multilayer. The figure which
shows the example which provided the electrode layer of the bridge structure in the circular
through hole. FIG. 1 is a block diagram showing the configuration of an ultrasonic speaker
according to the present invention. The figure which shows the use condition of the projector by
this invention. FIG. 10 is a view showing an appearance configuration of the projector shown in
FIG. 9; FIG. 10 is a block diagram showing an electrical configuration of the projector shown in
FIG. 9; Explanatory drawing of the reproduction | regeneration state of the reproduction |
regeneration signal by an ultrasonic transducer. The figure which shows the structure of the
conventional push pull type electrostatic ultrasound transducer.
Explanation of sign
[0103]
1, 2, 3 ... electrostatic ultrasonic transducer, 10 ... front side electrode, 11 ... vibrating film
support, 12 ... bridge, 13 ... opening (through hole), 14 ... electrode layer 20 ... back side electrode
21 ... vibrating membrane support part 22 ... bridge part 23 ... opening part (through hole) 24 ...
electrode layer 25 26, 27 ... plate-like fixing member 30, 30, 30A ... diaphragm, 31, 33, 35 ...
dielectric film, 32, 34 ... diaphragm electrode, 36 и и и DC power supply, 37 и и и Signal source 37A,
37B AC signal 40 Front side electrode 41 Reinforcing member 42A, 42B Electrode layer 50 Front
side electrode 51 5 2 и и Reinforcing member, 53A, 53B, 53C и и и Electrode layer, 60A и и и и и fixed
front surface side, 60B и и и и solid back side Electrodes 61A, 61B through holes 62 support
04-05-2019
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members 70 70A electrodes 71, 71A through holes 72 72A cross bridge portions 73 73A и и
Electrode layer, 101, 102 и и и Reflective plate, 201 и и и audio frequency wave oscillation source,
202 и и и carrier wave oscillation source, 203 и и и и и и и и и и и и и и и power amplifier иии Electrostatic
ultrasonic transducer, 301 иии Projector и и и и и и и (screen) (projection surface), 303 и и и и и и и и и и и и
310 operation input unit, и и и и и и и и и и playback range setting unit 313 ... playback range control
processing unit, 314 ... audio / video signal reproduction unit, 316 ... carrier wave oscillation
source, 317 A, 317 B ... high pass filter, 31 8 A, 318 B ... modulator, 319 и ииLow Sfilter 320,
projector main body 321 mixer 322A, 322B power amplifier 322C power amplifier 323, bass
reproduction speaker 324A, 324B ultrasonic wave Transducer, 331 иии Projector lens, 332 иии
Video generator, 333 и и и и Projection optical system
04-05-2019
37
It is an ultrasonic speaker that reproduces a signal sound in an audible
frequency band by driving a reducer, wherein the electrostatic ultrasonic transducer comprises: a
first electrode having a slit-like through hole; And the through hole of the first electrode and the
through hole of the second electrode are arranged in pairs, and the first electrode and the second
electrode And a conductive film having a conductive layer, wherein the conductive layer includes
a vibrating film to which a DC bias voltage is applied, the pair of electrodes being in the
longitudinal direction of the through hole in the through hole. Electrode layer placed on And a
convex portion of a plate-like fixing member having a convex shape is in contact with the vicinity
of the central portion of the surface of the one of the pair of electrodes opposite to the vibrating
membrane. A plate-like fixing member and the pair of electrodes are integrally fixed, and a
modulation wave obtained by modulating a carrier wave of an ultrasonic frequency band with an
audio frequency band is applied between the electrode layers of the pair of electrodes. It is
characterized by being. According to the ultrasonic speaker of the present invention configured
as described above, a carrier wave in the ultrasonic frequency band is modulated by a signal
wave in the audible frequency band, and the ultrasonic wave transducer is driven by the
modulated wave. An electrostatic ultrasonic transducer is used which has a slit-like through hole
in the electrode and has an electrode layer facing the vibrating film inside the through hole.
Thus, the vibration area of the vibrating film of the electrostatic ultrasonic transducer used for
the ultrasonic speaker can be increased, and the area of the opening for emitting the acoustic
signal can be increased. As a result, it is possible to realize an ultrasonic speaker capable of
generating an acoustic signal at a sound pressure level high enough to obtain a parametric array
effect over a wide frequency band. Further, the back center of one of the pair of electrodes
sandwiching the diaphragm of the electrostatic ultrasonic transducer used in the ultrasonic
speaker is in contact with the convex portion of the plate-like fixing member, It fixes so that the
peripheral part of an electrode may be pressed down with a screw etc. by the said plate-shaped
fixing member. As a result, the pair of electrodes in the electrostatic ultrasonic transducer is
configured such that the acoustic emission surface is slightly convex, and as a result, a
substantially uniform force is applied between the pair of electrodes, and the vibrating film has a
uniform force (distance). And stable membrane vibration is obtained.
[0025]
A sound signal reproducing method of an electrostatic ultrasonic transducer according to the
present invention comprises a first electrode having a slit-like through hole, a second electrode
having a slit-like through hole, and the penetration of the first electrode. A hole and a through
hole of the second electrode are arranged to form a pair, and are sandwiched by a pair of
electrodes consisting of the first electrode and the second electrode and having a conductive
layer, A vibrating membrane to which a direct current bias voltage is applied to the conductive
layer, the pair of electrodes including an electrode layer disposed in the longitudinal direction of
04-05-2019
10
the through hole inside the through hole, the pair of electrodes The convex portion of the platelike fixing member having a convex shape is brought into contact with the vicinity of the central
portion of the surface of the one of the electrodes opposite to the vibrating membrane so that the
plate-like fixing member and the pair of Electrostatic ultrasonic transducer which is fixed
integrally with the electrode A procedure of generating a signal wave in an audible frequency
band by a signal source, a procedure of generating a carrier wave of an ultrasonic frequency
band by a carrier wave source, and using the carrier wave as a signal in the audible frequency
band. A step of generating a modulation signal modulated by a wave, and a step of driving the
electrostatic ultrasonic transducer by applying the modulation signal between the electrode
layers of the pair of electrodes are characterized. In the sound signal reproduction method of the
electrostatic ultrasonic transducer including such a procedure, the carrier wave of the ultrasonic
frequency band is modulated by the signal wave of the audible frequency band, and the
electrostatic ultrasonic transducer is converted by the modulated wave. In an ultrasonic speaker
to be driven, an electrostatic ultrasonic transducer is used which has a slit-like through hole in
the electrode and an electrode layer facing the diaphragm inside the through hole. Thus, the
vibration area of the vibrating film of the electrostatic ultrasonic transducer used for the
ultrasonic speaker can be increased, and the area of the opening for emitting the acoustic signal
can be increased. As a result, it is possible to generate an acoustic signal with a sound pressure
level high enough to obtain a parametric array effect over a wide frequency band. Further, the
back center of one of the pair of electrodes sandwiching the diaphragm of the electrostatic
ultrasonic transducer used in the ultrasonic speaker is in contact with the convex portion of the
plate-like fixing member, It fixes so that the peripheral part of an electrode may be pressed down
with a screw etc. by the said plate-shaped fixing member. As a result, the pair of electrodes in the
electrostatic ultrasonic transducer is configured such that the acoustic emission surface is
slightly convex, and as a result, a substantially uniform force is applied between the pair of
electrodes, and the vibrating film has a uniform force (distance). And stable membrane vibration
is obtained.
[0026]
Further, the display device of the present invention modulates a carrier wave signal in an
ultrasonic frequency band with an audio signal supplied from an acoustic source, drives an
electrostatic ultrasonic transducer with the modulation signal, and thereby signals in an audible
frequency band. A display device comprising: an ultrasonic speaker for reproducing sound; and a
projection optical system for projecting an image on a projection surface, wherein the
electrostatic ultrasonic transducer of the ultrasonic speaker is a slit-like through hole. A first
electrode having a slit, a second electrode having a slit-like through hole, and the through hole of
the first electrode and the through hole of the second electrode are arranged in pairs; A
diaphragm including a conductive layer and being interposed between a pair of electrodes
04-05-2019
11
consisting of the first electrode and the second electrode, and a DC bias voltage being applied to
the conductive layer; The pole is inside the through hole It has an electrode layer arranged in the
longitudinal direction of the through hole, and a plate shape having a convex shape in the vicinity
of the central portion in the surface on the opposite side to the vibrating film of either one of the
pair of electrodes The plate-like fixing member and the pair of electrodes are integrally fixed so
that the convex portion of the fixing member abuts, and a carrier wave of an ultrasonic frequency
band is formed between the electrode layers of the pair of electrodes. A modulated wave
modulated by a signal wave in the audio frequency band is applied. In the display device having
the above configuration, an ultrasonic speaker is used which is configured of an electrostatic
ultrasonic transducer having a slit-like through hole in the electrode and an electrode layer
facing the vibrating film inside the through hole. . Then, the ultrasonic speaker reproduces the
audio signal supplied from the acoustic source. As a result, the sound signal can be reproduced
so as to be emitted from a virtual sound source formed in the vicinity of the sound wave
reflection surface such as a screen with sufficient sound pressure and wide band characteristics.
Therefore, control of the reproduction range of the sound signal can be easily performed.
Further, the back center of one of the pair of electrodes sandwiching the diaphragm of the
electrostatic ultrasonic transducer used in the ultrasonic speaker is in contact with the convex
portion of the plate-like fixing member, It fixes so that the peripheral part of an electrode may be
pressed down with a screw etc. by the said plate-shaped fixing member. As a result, the pair of
electrodes in the electrostatic ultrasonic transducer is configured such that the acoustic emission
surface is slightly convex, and as a result, a substantially uniform force is applied between the
pair of electrodes, and the vibrating film has a uniform force (distance). And stable membrane
vibration is obtained.
[0027]
Further, according to the directional acoustic system of the present invention, a carrier wave
signal of an ultrasonic frequency band is modulated by a signal of a first range of an audio signal
supplied from an acoustic source, and an electrostatic ultrasonic transducer is An ultrasonic
speaker driven to reproduce a signal sound in an audible frequency band; and a bass
reproduction speaker reproducing a signal in a second sound range lower than the first sound
range among audio signals supplied from the sound source. In the directional acoustic system,
the electrostatic ultrasonic transducer of the ultrasonic speaker includes: a first electrode having
a slit-like through hole; and a second electrode having a slit-like through hole A pair of electrodes
disposed such that the through hole of the first electrode and the through hole of the second
electrode form a pair, and including the first electrode and the second electrode Sandwiched And
a vibrating film to which a DC bias voltage is applied to the conductive layer, and the pair of
electrodes are electrode layers disposed in the longitudinal direction of the through hole inside
the through hole. A convex portion of a plate-like fixing member having a convex shape abuts on
04-05-2019
12
the vicinity of the central portion of the surface of the one of the pair of electrodes opposite to
the vibrating membrane. A modulation wave in which a plate-like fixing member and the pair of
electrodes are integrally fixed, and a carrier wave in an ultrasonic frequency band is modulated
by a signal wave in an audio frequency band between the electrode layers of the pair of
electrodes. Is applied. The directional acoustic system having the above configuration uses an
ultrasonic speaker including an electrostatic ultrasonic transducer having a slit-like through hole
in the electrode and an electrode layer facing the diaphragm inside the through hole. . Then,
among the audio signals supplied from the acoustic source, the ultrasonic speaker reproduces
the audio signal of the middle to high range (first range). Further, among the audio signals
supplied from the acoustic source, the audio signal in the low frequency range (second frequency
range) is reproduced by the bass reproduction speaker. Therefore, it is possible to reproduce the
sound in the middle to high frequency range so as to be emitted from a virtual sound source
formed in the vicinity of the sound wave reflection surface such as a screen with sufficient sound
pressure and wide band characteristics. In addition, since the low-range sound is directly output
from the low-range speaker in the sound system, the low-range sound can be enhanced, and a
more realistic sound environment can be created. Further, the back center of one of the pair of
electrodes sandwiching the diaphragm of the electrostatic ultrasonic transducer used in the
ultrasonic speaker is in contact with the convex portion of the plate-like fixing member, It fixes so
that the peripheral part of an electrode may be pressed down with a screw etc. by the said plateshaped fixing member.
As a result, the pair of electrodes in the electrostatic ultrasonic transducer is configured such that
the acoustic emission surface is slightly convex, and as a result, a substantially uniform force is
applied between the pair of electrodes, and the vibrating film has a uniform force (distance). And
stable membrane vibration is obtained.
[0028]
Hereinafter, embodiments of the present invention will be described in detail with reference to
the drawings. An example of the configuration of an electrostatic ultrasonic transducer according
to an embodiment of the present invention is shown in FIG. In the figure, reference numeral 1
denotes an electrostatic ultrasonic transducer, and the electrostatic ultrasonic transducer 1 has a
first electrode 10 having a through hole (not shown) and a second electrode having a through
hole (not shown). Of the first electrode 10, the through hole of the first electrode 10, and the
through hole of the second electrode 20, and the pair of electrodes comprising the first electrode
10 and the second electrode 20 And a conductive layer (not shown), and includes a vibrating film
30 to which a DC bias voltage is applied to the conductive layer.
04-05-2019
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[0029]
The pair of electrodes 10 and 20 are formed of a conductive material, or have an electrode layer
facing the vibration film 30 inside the through hole, and any one of the pair of electrodes 10 and
20 is provided. Of the plate-like fixing member 25 having a convex shape (for example, a convex
curved surface) in the vicinity of the central portion of the surface of the electrode (in the present
embodiment, the second electrode 20) opposite to the vibrating film 30 The plate-shaped fixing
member 25 and the pair of electrodes 10 and 20 are integrally fixed by the screw 28 such that a
convex portion (for example, a convex curved surface) abuts. The plate-like fixing member 25 is
formed of a member having a rigidity equal to or higher than that of the pair of electrodes 10
and 20.
[0030]
With the above configuration, the back center of one of the pair of electrodes sandwiching the
diaphragm is in contact with the convex portion (for example, a convex curved surface) of the
plate-like fixing member 25, and the pair of electrodes 10 and 20 It fixes so that the peripheral
part of this may be pressed down with the screw 28 by the said plate-shaped fixing member 25.
As shown in FIG. As a result, the pair of electrodes 10 and 20 in the electrostatic ultrasonic
transducer 1 is configured such that the acoustic emission surface is slightly convex, and as a
result, a substantially uniform force is applied between the pair of electrodes 10 and 20. The
vibrating membrane 30 is held with uniform force (distance), and stable membrane vibration can
be obtained.
[0031]
When the electrostatic ultrasonic transducer 1 is driven, a DC bias voltage is applied to the
conductive layer of the vibrating film 30, and between the pair of electrodes 10 and 20 or
between the pair of electrodes 10 , 20, a modulated wave obtained by modulating a carrier wave
in the ultrasonic frequency band with a signal wave in the audible frequency band is applied.
[0032]
Next, another configuration of the electrostatic ultrasonic transducer according to the
embodiment of the present invention is shown in FIG.
04-05-2019
14
In the figure, the only difference from the electrostatic ultrasonic transducer shown in FIG. 1 in
the configuration is the shape of the plate-like fixing member, and the other configurations are
the same. In the electrostatic ultrasonic transducer 1 shown in FIG. 2, the plate-like fixing
member 26 is the vibrating film 30 of either one of the pair of electrodes 10 and 20 (the second
electrode 20 in the present embodiment). A projection 26A is provided at the central portion of
the surface of the plate-like fixing member 26 that abuts the opposite surface. 29 is a screw hole.
[0033]
With the above configuration, the back center of one of the pair of electrodes 10 and 20
sandwiching the diaphragm 30 abuts on the protrusion 26A formed at the central portion of the
plate-like fixing member 26, The peripheral portion 20 is fixed so as to be pressed down by the
screw 28 by the plate-like fixing member 26. As a result, the pair of electrodes in the electrostatic
ultrasonic transducer is configured such that the acoustic emission surface is a light convex
surface, and as a result, a substantially uniform force is applied between the pair of electrodes 10
and 20, and the diaphragm 30 is uniform. It is possible to obtain stable membrane vibration by
holding it with a constant force (distance). In the examples shown in FIGS. 1 and 2, the first
electrode 10, the second electrode, and the plate-like fixing member (25 or 26) are integrally
fixed by screws, but the present invention is limited thereto. Alternatively, they may be fixed by
an adhesive or the like.
[0034]
In addition, the plate-like fixing member which applies stress to the first electrode 10 and the
second electrode so that the acoustic radiation surface is convex and fixes them integrally is
limited to the shape shown in FIG. 1 and FIG. Alternatively, for example, as shown in FIG. 3, a
plate-like fixing member may be provided having a band-like protrusion 27A having a
semicircular cross section at the center. The first electrode 10 and the second electrode 20 of the
electrostatic ultrasonic transducer 1 are integrally fixed with the plate-like fixing member shown
in FIG. 3 instead of the plate-like fixing member shown in FIGS. Even in this case, the same effect
as obtained by the configuration of FIGS. 1 and 2 can be obtained. In addition, 29 is a screw hole.
04-05-2019
15
[0035]
The fixing structure of the electrostatic ultrasonic transducer according to the present
embodiment shown in FIGS. 1 to 3 described above can be all applied if already described, and
the electrostatic ultrasonic transducer of FIG. Also applies to The configuration and operation of
the electrostatic ultrasonic transducer have already been described for the electrostatic
ultrasonic transducer in FIG. 13, so the description will be omitted here. The electrostatic
ultrasonic transducer in FIGS. 1 to 3 conceptually shows a push-pull type electrostatic ultrasonic
transducer.
[0036]
Next, a specific configuration example of an electrostatic ultrasonic transducer to which the
present invention (a structure in which a pair of electrodes are integrally fixed by a plate-like
fixing member as shown in FIGS. 1 to 3) is applied is shown in FIG. Shown in. However, the state
fixed by the plate-like reinforcing member is omitted. FIG. 4A is a cross-sectional view, and FIG.
4B is a plan view of the electrode viewed from the vibrating film side.
[0037]
The electrostatic ultrasonic transducer 1 to which the present invention is applied includes a
vibrating membrane 30 and a front side electrode (first electrode) 10 and a back side electrode
(second electrode) 20 which are a pair of electrodes for holding the vibrating membrane 30. And
the circuit that drives it.
[0038]
The front side electrode 10 has a vibrating membrane support portion 11 for holding the
vibrating membrane 30, an opening 13 which is a slit-like (rectangular) through hole, and the
through hole inside the opening (through hole) 13. And a bridge portion 12 disposed parallel to
the longitudinal direction.
The bridge portion 12 is arranged such that its bottom surface (the diaphragm facing surface
facing the diaphragm 30) maintains a predetermined distance (for example, 5 to 6 ?m) with the
surface of the diaphragm 30 when not vibrating. Ru. Further, an electrode layer 14 is formed on
04-05-2019
16
the diaphragm facing surface facing the diaphragm 30 of the bridge portion 12.
[0039]
Similarly, the back side electrode 20 includes a vibrating membrane support 21 for holding the
vibrating membrane 30, an opening 23 which is a slit-like (rectangular) through hole, and an
opening 23 (through hole) In the inside, it is formed of a bridge portion 22 disposed parallel to
the longitudinal direction of the through hole. The bridge portion 22 is arranged such that its
bottom surface (the vibrating film facing surface facing the vibrating film 30) holds a
predetermined distance (for example, 5 to 6 ?m) with the film surface of the vibrating film 30
when not vibrating. Ru. Also, an electrode layer 24 is formed on the diaphragm facing surface
facing the diaphragm 30 of the bridge portion 22.
[0040]
The thickness of the front side electrode 10 and the back side electrode 20 is, for example, about
1.5 mm. Further, as shown in FIG. 4B, the width of the slit-like through hole is, for example, about
1.5 mm, and the width of the bridge portion is about 0.5 mm.
[0041]
The front side electrode 10 and the rear side electrode 20 are formed of a nonconductive base
material (various plastics, glass, ceramics, etc.), and plated and printed with metal (gold, silver,
copper, aluminum etc.) as the electrode layers 14, 24. , Vapor deposition, paste, etc. An AC
voltage of about 10 to 300 V is applied to the electrode layers 14 and 24 by AC signals 37A and
37B on the circuit side.
[0042]
The vibrating film 30 is formed by covering the vibrating electrode (conductive layer) 32 with
the dielectric films (insulators) 31 and 32. For example, a metallized one side of a polymer film
(dielectric film) having a thickness of several microns is laminated with an adhesive. As a material
of the polymer film, for example, poly ethylene terephthalate (PET), aramid, poly ester, poly
04-05-2019
17
ethylene naphthalate (PEN), poly phenylene sulfide (PPS) or the like is used. The material of the
metallized portion forming the vibrating electrode 32 is most commonly Al (aluminum), and may
be Ni, Cu, SUS, Ti or the like. The thickness of the metallized portion is preferably about 100 ┼ to
1,500 ┼. A DC bias voltage of 10 to 300 V is applied to the metallized portion (the vibrating
electrode 32) of the vibrating membrane from the DC power supply 36 on the circuit side.
[0043]
The operation of the electrostatic ultrasonic transducer 1 of the above configuration is basically
the same as that of the electrostatic ultrasonic transducer 3 shown in FIG. 13, and an acoustic
signal is generated by the push-pull operation of the vibrating membrane 30. Do. That is, in the
electrostatic ultrasonic transducer 1, the pair of electrodes 10, 20 have the same number and
plural slit-like openings (through holes) 13, 23 at the positions facing each other through the
vibrating film 30. Between the electrode layers 14 and 24 of the bridge portions 12 and 22 of
the pair of electrodes 10 and 20, alternating current signals 37A and 37B which are mutually
phase-inverted by the signal source 37 are applied. Capacitors are formed between the electrode
layer 14 and the vibrating electrode 32, and between the electrode layer 24 and the vibrating
electrode 32, respectively. Further, a DC bias voltage of a single polarity (positive in this
embodiment) is applied to the vibrating electrode 32 of the vibrating membrane 30 by the DC
power supply 36.
[0044]
As a result, in the positive half cycle of the alternating current signal 37A output from the signal
source 37, a positive voltage is applied to the electrode layer 14 of the bridge portion 12 of the
front side electrode 10. The electrostatic repulsion force acts on the surface portion 15A which is
not sandwiched by 20, and the surface portion 15A is pulled downward in FIG. At this time, the
alternating current signal 37B has a negative cycle, and a negative voltage is applied to the
electrode layer 24 of the bridge portion 22 of the opposing back side electrode 20, so that the
surface portion 15A of the diaphragm 30 is The electrostatic attraction force acts on the back
surface portion 15B which is the back surface side, and the back surface portion 15B is pulled
further downward in FIG.
[0045]
04-05-2019
18
Therefore, the film portion of the vibrating film 30 which is not held by the pair of electrodes 10
and 20 receives electrostatic attraction force and electrostatic repulsion force (electrostatic
repulsive force) in the same direction. Similarly, for the negative half cycle of the alternating
current signal output from the signal source 37, the surface portion 15A of the vibrating
membrane 30 in FIG. In FIG. 4, electrostatic repulsive force acts on the upper side, and a film
portion of the vibrating film 30 which is not sandwiched by the pair of electrodes 10 and 20
receives electrostatic attractive force and electrostatic repulsive force in the same direction. In
this manner, the vibrating film 30 receives the electrostatic attraction force and the electrostatic
repulsion force in the same direction according to the change of the polarity of the alternating
current signal, and the direction in which the electrostatic force acts alternately changes. That is,
acoustic signals at sound pressure levels sufficient to obtain a parametric array effect can be
generated. The acoustic signal emitted from the vibrating film 30 is emitted to the outside as a
plane wave through the slit-like openings 13 and 23.
[0046]
FIG. 5 is a view showing a modification of the electrostatic ultrasonic transducer to which the
present invention is applied. FIGS. 5A, 5B, and 5C are plan views of the front side electrode as
viewed from the vibrating film side. In addition, a back side electrode also becomes the same
structure.
[0047]
The front side electrode 10 shown in FIG. 5A is the same as the front side electrode 10 shown in
FIG. 4B, and is the most basic configuration example of the electrostatic ultrasonic transducer to
which the present invention is applied. is there.
[0048]
The front side electrode 40 shown in FIG. 5 (B) has a reinforcing member 41 for reinforcing a
base material (for example, plastic etc.) forming the electrode, in the central portion of the slitlike through hole in the longitudinal direction. An example is shown in which it is added in the
direction orthogonal to the longitudinal direction of.
In this example, an example is shown in which the electrode layer facing the diaphragm is
divided into two by the reinforcing member 41 into the electrode layer 42A and the electrode
04-05-2019
19
layer 42B. However, the length of the reinforcing member 41 (the depth of the through hole is
The length in the direction is made the same as the length of the bridge (the length in the depth
direction of the through hole), and the surface of the bridge (the surface facing the diaphragm)
and the surface of the reinforcing member 41 are aligned. Can also be formed as a continuous
surface.
[0049]
Further, the front side electrode 50 shown in FIG. 5C has two reinforcing members 51 and 52 for
reinforcing a base material (for example, plastic etc.) forming the electrode, and a slit-like
through hole is even. An example is shown in which the length is added. In this example, an
example is shown in which the electrode layer facing the diaphragm is divided into three into the
electrode layer 53A, the electrode layer 53B, and the electrode layer 53C by the reinforcing
members 51 and 52. The length of the through hole (the depth direction of the through hole) is
the same as the length of the bridge (the length of the through hole in the depth direction), and
the surface of the bridge (the surface facing the diaphragm) and the reinforcing member The
electrode layer can also be formed as a continuous surface by combining the surfaces 51 and 52.
[0050]
As described above, when the transducer area is small, a slit-like rectangular hole (through hole)
as shown in FIG. 5A may be formed, but the transducer area is increased and the mechanical
strength of the electrode is secured. If necessary, as shown in FIGS. 2B and 2C, the base material
is reinforced in the direction perpendicular to the longitudinal direction of the through hole at
the middle of the slit. This makes it possible to increase the strength of the electrode of the
electrostatic ultrasonic transducer, and makes it possible to manufacture an electrostatic
ultrasonic transducer with a large area (for example, 50 mm О 50 mm or more).
[0051]
The structure of the electrostatic ultrasonic transducer to which the present invention is applied
has been described above. The feature of an example of the electrostatic ultrasonic transducer to
which the present invention shown in FIG. 4 is applied is shown in FIG. As shown in (B) and (C), it
is necessary to open a through hole (opening) in a rectangular shape (slit shape) in a pair of
04-05-2019
20
electrodes, and it is particularly important that the electrode is placed against the center of the
rectangular diaphragm. In order to form a layer, a base material (bridge portion) for forming an
electrode pattern in a bridge shape is to be left. This results from expanding the bridge structure
for round holes shown in FIG. 7 into rectangular holes.
[0052]
Here, the configuration of an electrostatic ultrasonic transducer in which an electrode layer
having a bridge structure is provided in a circular through hole shown in FIG. 7 will be described.
FIG. 7A is a plan view of the pair of electrodes 70 sandwiching the diaphragm, one of the
electrodes 70A viewed from the diaphragm side. FIG. 7B is a cross-sectional view of the
electrostatic ultrasonic transducer, and is a cross-sectional view in the XX ? direction in FIG. 7A.
[0053]
In this electrostatic ultrasonic transducer, a circular through hole 71 is provided in an electrode
(base material) 70 formed of a nonconductive material, and a cruciform bridge portion 72 facing
the diaphragm 30 in the circular through hole 71 is provided. Is provided. The cross bridge
portion 72 is formed such that its length (the length in the depth direction of the through hole)
has a predetermined distance (for example, 5 to 6 ?m) from the surface of the vibrating
membrane 30 when it is not vibrating. An electrode layer 73 is formed on the surface of the
cross bridge 72 facing the vibrating membrane 30. Similarly, a through hole 71A, a cross bridge
portion 72A, and an electrode layer 73A are formed in the other electrode 70A. Then, a direct
current bias voltage is applied to the vibrating electrode 32 of the vibrating film 30, and an
alternating current signal is applied between the cross-shaped electrode layer 73 and the
electrode layer 73A.
[0054]
Such a structure makes it possible to efficiently convert electrical energy into film vibration
energy (to obtain an acoustic signal with a large amplitude).
[0055]
The structure shown in FIG. 7 is such that the electrode layer is formed in a cross bridge shape
04-05-2019
21
with respect to a round hole (for example, ? 0.75 mm), but the aperture ratio (the area ratio of
acoustic energy radiation) is 15% or less .
On the other hand, when an electrode layer of a bridge structure is applied to a rectangular
through hole as in the electrostatic ultrasonic transducer of the present invention, the vibration
area of the diaphragm can be approximately tripled, and An aperture ratio of 3 times (45%) can
be obtained. The meaning of this number is that the rectangular bridge structure of the present
invention is capable of emitting three times as much acoustic energy when the membrane
amplitude of both the round hole and the rectangular hole is the same. is there.
[0056]
Further, in the electrodes 10 and 20 of the electrostatic ultrasonic transducer of the present
invention shown in FIG. 4, the configuration of the bridge portion in the through hole is simple as
compared with the electrode 70 of the electrostatic ultrasonic transducer shown in FIG. This
makes it easy to manufacture the electrode.
[0057]
Furthermore, in order to further increase the electrostatic force, it is also effective to form the
vibrating film 30A in a laminated structure of three or more layers.
That is, as in the case of the electrostatic ultrasonic transducer 2 shown in FIG. 6, the
electrostatic force is formed by laminating the two vibration electrodes 32, 34 and the dielectric
films 31, 33, 35 to form the vibration film 30A. To increase the membrane amplitude.
[0058]
As described above, in the electrostatic ultrasonic transducer according to the present invention,
the vibration area of the vibrating film is increased by making the vibrating shape of the
vibrating film into a rectangular shape (slit shape), and the opening for emitting an acoustic
signal. Increase the area of Therefore, a large amplitude acoustic signal can be obtained with a
low voltage signal. As a result, the electrical / acoustic energy conversion efficiency can be
improved to obtain an acoustic signal with high sound pressure.
04-05-2019
22
[0059]
In addition, an electrostatic ultrasonic transducer to which the present invention is applied
includes a first electrode having a slit-like through hole, a second electrode having a slit-like
through hole, and the first electrode. A through hole and the through hole of the second
electrode are arranged to form a pair, and are sandwiched by a pair of electrodes consisting of
the first electrode and the second electrode, and have a conductive layer. A vibrating membrane
to which a DC bias voltage is applied to the conductive layer, the pair of electrodes including an
electrode layer disposed in the longitudinal direction of the through hole inside the through hole,
the pair of electrodes The convex portion of the plate-like fixing member having a convex shape
is brought into contact with the vicinity of the central portion of the surface on the opposite side
to the vibrating film of any one of the electrodes, and the plate-like fixing member The pair of
electrodes is integrally fixed to the pair of electrodes. The kicking the electrode layers modulated
wave obtained by modulating the carrier wave in the ultrasonic frequency band by signal waves
in the audio frequency band is applied.
[0060]
With the above configuration, the back center of one of the pair of electrodes sandwiching the
diaphragm is in contact with the convex portion of the plate-like fixing member, and the
peripheral portion of the pair of electrodes is screwed by the plate-like fixing member. It is fixed
so that it can be pressed down by.
As a result, the pair of electrodes in the electrostatic ultrasonic transducer is configured such that
the acoustic emission surface is slightly convex, and as a result, a substantially uniform force is
applied between the pair of electrodes, and the vibrating film has a uniform force (distance). And
stable membrane vibration is obtained.
[0061]
Further, in the electrostatic ultrasonic transducer according to the present invention, the platelike fixing member is a member of the plate-like fixing member which is in contact with the
surface of either one of the pair of electrodes opposite to the vibrating membrane. The surface is
formed as a convex curved surface. With the above configuration, the back center of one of the
pair of electrodes sandwiching the diaphragm contacts the convex surface of the plate-like fixing
member, and the peripheral portion of the pair of electrodes is screwed by the plate-like fixing
04-05-2019
23
member. It is fixed so as to be held down. As a result, the pair of electrodes in the electrostatic
ultrasonic transducer is configured such that the acoustic emission surface is slightly convex, and
as a result, a substantially uniform force is applied between the pair of electrodes, and the
vibrating film has a uniform force (distance). And stable membrane vibration is obtained.
[0062]
Further, in the electrostatic ultrasonic transducer according to the present invention, the platelike fixing member is a member of the plate-like fixing member which is in contact with the
surface of either one of the pair of electrodes opposite to the vibrating membrane. It has a
protrusion at the center of the surface. With the above configuration, the back center of one of
the pair of electrodes sandwiching the diaphragm contacts the protrusion formed at the center of
the plate-like fixing member, and the peripheral portion of the pair of plates is the plate-like. It is
fixed so that it can be pressed down by a screw etc. by a fixing member. As a result, the pair of
electrodes in the electrostatic ultrasonic transducer is configured such that the acoustic emission
surface is slightly convex, and as a result, a substantially uniform force is applied between the
pair of electrodes, and the vibrating film has a uniform force (distance ) And stable membrane
vibration can be obtained.
[0063]
Next, a configuration example of an ultrasonic speaker using an electrostatic ultrasonic
transducer to which the present invention is applied is shown in FIG. The ultrasonic speaker
according to the present embodiment has the above-described electrostatic ultrasonic transducer
of the present invention (FIG. 4), that is, a slit-like through hole (opening), and an electrode at the
bridge in the through hole. It is composed of a Push-Pull type electrostatic ultrasonic transducer
provided with a layer. This electrostatic ultrasonic transducer is a plate-like fixing member shown
in FIGS. 1 to 3, and a pair of electrodes are integrally fixed so that the acoustic radiation surface
has a convex shape. The figure does not show this condition for the sake of convenience.
[0064]
In FIG. 8, the ultrasonic speaker according to this embodiment includes an audio frequency wave
oscillation source 201 that generates a signal wave in an audio wave frequency band, and a
carrier wave oscillation that generates and outputs a carrier wave in an ultrasonic frequency
04-05-2019
24
band. A source 202, a modulator 203, a power amplifier 204, and an electrostatic ultrasonic
transducer 205 are included. The modulator 203 modulates the carrier wave output from the
carrier wave oscillation source 202 with the signal wave in the audio wave frequency band
output from the audio frequency wave oscillation source 201, and the electrostatic ultrasonic
wave is transmitted through the power amplifier 204. The transducer 205 is supplied.
[0065]
In the above configuration, the carrier wave in the ultrasonic frequency band output from the
carrier wave oscillation source 202 is modulated by the modulator 203 by the signal wave
output from the audio frequency wave oscillation source 201, and the modulation signal
amplified by the power amplifier 204. The electrostatic ultrasonic transducer 205 is driven. As a
result, the modulated signal is converted into a sound wave of a finite amplitude level by the
electrostatic ultrasonic transducer 205, and this sound wave is emitted into the medium (in air)
and the original audible can be heard by the nonlinear effect of the medium (air). Signal sound in
the frequency band is self-reproduced.
[0066]
That is, since the sound wave is a compression wave propagating through the air as a medium, in
the process of propagating the modulated ultrasonic wave, the dense part and the sparse part of
the air appear prominently, and the sound speed is high at the dense part. Since the sound
velocity of the sparse part is slowed, distortion occurs in the modulated wave itself, and as a
result, the waveform is separated into the carrier wave (ultrasonic frequency band), and the
signal wave (sound signal) in the audible wave frequency band is reproduced.
[0067]
As the electrostatic ultrasonic transducer 205, the electrostatic ultrasonic transducer 1 of the
present invention shown in FIG. 4 is used, and an acoustic signal of high sound pressure can be
outputted with a wide band.
Therefore, it can be used as a speaker for various applications.
[0068]
04-05-2019
25
Ultrasonic waves are highly attenuated in the air and decay in proportion to the square of their
frequency. Therefore, when the carrier frequency (ultrasound) is low, it is possible to provide an
ultrasonic speaker that can transmit sound in the form of a beam with less attenuation.
Conversely, if the carrier frequency is high, the attenuation is so severe that the parametric array
effect does not occur sufficiently, and it is possible to provide an ultrasonic speaker in which the
sound spreads. These are very effective functions because they can be used with the same
ultrasonic speaker depending on the application.
[0069]
Further, since the electrostatic ultrasonic transducer 1 of the present invention shown in FIG. 4 is
used for this ultrasonic speaker, one of the pair of electrodes sandwiching the vibrating film of
the electrostatic ultrasonic transducer is used. The central portion of the back face is in contact
with the convex portion of the plate-like fixing member, and the peripheral portions of the pair of
electrodes are fixed so as to be pressed down by the screw or the like by the plate-like fixing
member. As a result, the pair of electrodes in the electrostatic ultrasonic transducer is configured
such that the acoustic emission surface is slightly convex, and as a result, a substantially uniform
force is applied between the pair of electrodes, and the vibrating film has a uniform force
(distance ), And stable membrane vibration is obtained.
[0070]
Next, the electrostatic ultrasonic transducer according to the present invention, that is, having a
slit-like through hole (opening), having an electrode layer at the bridge in the through hole, and
having a pair of electrodes by a plate-like fixing member A directional acoustic system using an
ultrasonic speaker composed of a physically fixed Push-Pull type electrostatic ultrasonic
transducer (FIG. 4) will be described. The electrostatic ultrasonic transducer is hereinafter also
simply referred to as "ultrasonic transducer".
[0071]
Hereinafter, a projector (display device) will be described as an example of the directional
acoustic system according to the present invention. FIG. 9 shows the use of the projector
04-05-2019
26
according to the present invention. As shown in the figure, the projector 301 is installed behind
the viewer 303 and projects an image on the screen 302 installed in front of the viewer 303, and
the screen 302 by the ultrasonic speaker mounted on the projector 301. The virtual sound
source is formed on the projection plane of the to reproduce the sound.
[0072]
The external configuration of the projector 301 is shown in FIG. The projector 301 includes a
projector main body 320 including a projection optical system for projecting an image on a
projection surface such as a screen, and ultrasonic transducers 324A and 324B capable of
emitting sound waves in an ultrasonic frequency band, and includes an acoustic source An
ultrasonic speaker that reproduces a sound signal of an audible frequency band from a supplied
audio signal is integrally configured. In the present embodiment, in order to reproduce a stereo
sound signal, ultrasonic transducers 324A and 324B constituting ultrasonic speakers on the left
and right sides of the projector lens 331 constituting the projection optical system are mounted
on the projector main body. . Furthermore, on the bottom surface of the projector main body
320, a bass reproduction speaker 323 is provided. Further, reference numeral 325 denotes a
height adjustment screw for adjusting the height of the projector main body 320, and reference
numeral 326 denotes an exhaust port for an air cooling fan.
[0073]
Further, in the projector 301, as an ultrasonic transducer constituting an ultrasonic speaker, a
Push-Pu
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