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BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an
ultrasonic microphone, and more particularly to a structure of an ultrasonic microphone for
detecting ultrasonic energy emitted from a temperature or pressure sensor in a living body on
the living body surface. (Prior Art) In recent years, research on biological and medical research
has been conducted for a long time without a power source sensor embedded in a living body for
measuring the temperature or pressure of each part in the living body especially for the purpose
of treating cancer etc. There has been proposed a method of measuring without connecting by
wire between devices. As a temperature measurement or pressure measurement method as
mentioned above. A sensor in which a quartz oscillator and an ultrasonic transducer are
connected to an antenna coil is surgically implanted at a required position in the living body,
electromagnetic energy of a required frequency is irradiated from outside the living body, and
the energy is transmitted through the antenna coil. There is a method of observing from outside
the ultrasound generated by controlling the ultrasonic transducer by the current given to the
quartz oscillator and resonating with the oscillator (see Japanese Patent Application No. 60021542). . A temperature or pressure sensor used at this time and a pickup device for detecting
an ultrasonic wave emitted from the sensor from outside the body are generally as shown in FIG.
2 (a). That is, in the figure, X is a quartz oscillator having a series resonance point in the vicinity
of 8 MHz, and the antenna coil L1 and the ultrasonic transducer SW are connected in a closed
loop to form a sensor and a required part in the living body At the same time as the transmitter is
composed of a variable frequency oscillator 1 and a frequency meter 2 which embeds an antenna
coil L2 on the surface of the living body nearest to the sensor and embeds it into the sensor, the
sensor coil is generated. In the measurement, the above-mentioned sensor is irradiated with the
output of the variable frequency oscillator 1 through the antenna coil L2 connected thereto, and
the ultrasonic wave generated by the sensor is received by the microphone 3 and the electric
signal is received. In the high frequency amplifier 4, the oscillation frequency of the variable
frequency excavating device 1 is changed while being amplified to a required level and then
monitored by the level meter 6, so that the reading of the level meter is maximized. The resonant
frequency of the child can be detected. Therefore, if the relationship between the resonant
frequency of the quartz oscillator X incorporated in the above-mentioned sensor and the
temperature or pressure is known, the temperature or pressure in the living body can be
accurately measured. Among the devices used for such measurements, the external device, in
particular the structure of the ultrasonic microphone, is conventionally fixed to an appropriate
frame 8 simply by using an ultrasonic transducer 7 such as barium titanate as shown in FIG.
Were common.
However, since the acoustic impedances of the ultrasonic transducer and the surface of the living
body are different, the microphone of such structure has a drawback that the propagation loss of
the ultrasonic wave becomes large and the microphone output is reduced only by bringing the
two into direct contact. In order to alleviate these drawbacks, acoustic matching has been carried
out by applying oil, water, etc. between the microphone receiving surface and the living body
surface. The output changes with movement, and the ice dries quickly and the oil is not easy to
remove, and it has the disadvantage of making the subject feel uncomfortable. OBJECTS OF THE
INVENTION The present invention was made to eliminate the disadvantages of the prior art
microphones as described above. An object of the present invention is to provide an ultrasonic
microphone which is suitable for stably detecting an ultrasonic signal through the surface of a
living body and which can improve measurement sensitivity. SUMMARY OF THE INVENTION For
this reason, the microphone according to the present invention has an acoustic matching
material rich in flexibility, such as agar, for example, in contact with the surface of the transducer
for acoustic matching between the ultrasonic transducer and the living body surface. At the same
time, the free surface of the acoustic matching material is covered with a vinyl sheet or the like to
present invention will be described in detail based on the illustrated and illustrated embodiments.
1 (at and (bl are respectively a cross-sectional view and a front view showing one embodiment of
the present invention). In the figure, reference numeral 7 denotes an ultrasonic transducer fixed
to the opening of the metal case 8. A piezoelectric material such as barium titanate is processed
to a desired thickness and electrodes 9 and 9 for charge extraction are provided on both sides.
One of them is used as a direct hot terminal and the other as a cold terminal through the case 8.
Further, the acoustic matching material 10 such as agar is in contact with the sound receiving
surface of the piezoelectric material 7 except the opening of the metal case 8 and the tip end face
of the acoustic matching material slightly protrudes from the front surface of the metal case 8.
Do. The free surface of the acoustic matching material is covered with the resin sheet 11 to
maintain the shape of the acoustic matching material 1 ° and prevent evaporation of the liquid
(water, oil, etc.) contained therein. The present invention may be modified as follows. That is, FIG.
3 (al and (b) are cross-sectional views showing other embodiments of the microphone according
to the present invention, respectively, in which the shape of the acoustic matching material is a
concave lens 12 or a convex lens 13 shape. This makes it possible to control the directivity of the
ultrasonic transducer, and to improve the sensitivity and S / N.
The shape of the microphone receiving surface can be easily realized because the acoustic
matching material is a gelatinous material which can generally maintain the desired shape under
no load condition, but it is possible to significantly change the shape. It is needless to say that the
resin coating 11 may be made of a resin material having appropriate elasticity and flexibility to
prevent the resin coating 11 from being blocked. (Effects of the Invention) Since the present
invention is configured as described above, the sound reception of the ultrasonic microphone
positioned on the surface of the living body to achieve ultrasonic coupling with the sensor such
as temperature or pressure embedded in the living body The surface can be made flexible
enough to match the impedance with the surface of the living body, and it can be adapted to the
unevenness of the surface of the living body to increase the degree of adhesion, thereby reducing
acoustic loss and stabilizing under high S / N. Exert significant effects on the measurement.
Brief description of the drawings
1 (a) and ((bl is a plan view and a sectional view showing an embodiment of the present
invention, respectively; FIG. 2 (al and (bl is a principle diagram showing one implementation
method of in-vivo temperature measurement; FIG. 3 is a cross-sectional view of a sound wave
microphone (al and (bl are cross-sectional views showing other embodiments of the present
invention, respectively).
3 ··········· Ultrasonic microphone 7 ·········· Ultrasonic transducer (barium titanate vibrator) 8 ·········
Metal case, 9 ··· --- ... electrode.
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