JPS635700A - Ultrasonic microphone - Google Patents

Abstract

PURPOSE:To stably detect an ultrasonic signal and to improve measurement sensitivity by abutting acoustic matching material which is rich in flexibility like vegitable gelatin, etc., against the surface of a transducer and covering the free face of the acoustic matching material with a vinyl sheet. CONSTITUTION:Piezoelectric material such as barium titanate, etc., is processed into a desirable thickness and electrodes 9 and 9 for charge fetching are provided on both sides, one of which is directly set as a hot terminal and other is set as a cold terminal through a case 8. And to the sound receiving face of piezoelectric material 7 which peeps from the aperture of a metallic case 8, the acoustic matching material 10 such as vegitable gelatin, etc. is abutted and the end face of the acoustic matching material 10 is set to be protruded a little ahead of the metallic case 8. Then the free face of the acoustic matching material is covered with a resin sheet 11, so that the shape of the acoustic matching material 10 can be kept and the evaporation of liquid contained inside can be prevented.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to an ultrasonic microphone, particularly an ultrasonic microphone for detecting ultrasonic energy emitted from a temperature or pressure sensor inside a living body on the surface of the living body. Regarding structure.

(Prior art) In recent years, biological and medical research equipment has been used to measure the temperature or pressure of various parts of the body, especially for the purpose of cancer treatment, etc., and to use non-powered sensors implanted in the body for a long period of time and measurements outside the body. A method has been proposed in which measurements can be made without a wired connection to the device.

As a method for measuring temperature or pressure as described above.

A sensor in which a crystal oscillator and an ultrasonic transducer are connected to an antenna coil is surgically implanted at a desired position within a living body, and electromagnetic energy of a desired frequency is irradiated from outside the living body, and the energy is transmitted through the antenna coil. There is a method of observing the ultrasonic waves generated from outside the living body by controlling the ultrasonic transducer using a current applied to the crystal oscillator and causing the oscillator to resonate with the current (see Japanese Patent Application No. 60-021542). .

The temperature or pressure sensor used at this time and the pickup device for detecting the ultrasonic waves emitted from the sensor from outside the living body are generally shown in FIG. 2(a).

That is, in the same figure, X is a crystal oscillator with a series resonance point near 8 MHz, and an antenna coil L1 and an ultrasonic transducer SW are connected to this crystal oscillator to form a closed loop, and the sensor is used as a sensor at the desired part in the living body. While implanting the sensor, an antenna coil L2 is placed on the surface of the living body closest to the sensor, and a transmitting section consisting of a variable frequency oscillator 1 and a frequency meter 2 that generate electromagnetic waves of around 8 MHz generates ultrasonic waves.

During the measurement, the output of the variable frequency oscillator 1 is irradiated to the above-mentioned sensor via the antenna coil L2 connected thereto, and the ultrasonic waves oscillated by the sensor are received by the microphone 3 and the electrical signals thereof are received. The oscillation frequency of the variable frequency excavator 1 is changed while the high frequency amplifier 4 amplifies the frequency to a required level, and the level meter 6 monitors the oscillation frequency. The resonant frequency of the child can be detected.

Therefore, if the relationship between the resonance frequency of the crystal oscillator X incorporated in the sensor described above and the temperature or pressure is known, the temperature or pressure inside the living body can be accurately measured.

Conventionally, the structure of an external device, especially an ultrasonic microphone, among devices used for such measurements is simply an ultrasonic transducer 7 made of barium titanate or the like fixed to a suitable frame 8, as shown in FIG. Those that did were common.

However, a microphone with such a structure has the disadvantage that the acoustic impedance of the ultrasonic transducer and the surface of the living body is different, so that simply bringing the two into direct contact with each other increases the propagation loss of the ultrasonic waves and lowers the microphone output. In order to alleviate these drawbacks, methods have been used to achieve acoustic matching by applying oil or water between the microphone sound-receiving surface and the surface of the living body. There are disadvantages such as the output changes depending on movement, ice dries quickly, and oil is difficult to remove and causes discomfort to the person being measured.

(Object of the Invention) The present invention has been made in order to eliminate the drawbacks of conventional microphones as described above.

An object of the present invention is to provide an ultrasonic microphone that is suitable for stably detecting ultrasonic signals via the surface of a living body and is capable of improving measurement sensitivity.

(Summary of the Invention) Therefore, in order to achieve acoustic matching between the ultrasonic transducer and the biological surface, the microphone according to the present invention abuts a highly flexible acoustic matching material such as agar on the surface of the transducer. At the same time, the free surface of the acoustic matching material is covered with a vinyl sheet or the like to form a magnetic structure.

(Embodiments of the Invention) The present invention will be described in detail below based on illustrated embodiments.

FIG. 1 (at and (bl) are a sectional view and a front view, respectively, showing one embodiment of the present invention.

In the figure, 7 is an ultrasonic transducer fixed to the opening of a metal case 8, made of a piezoelectric material such as barium titanate processed to a desired thickness, and provided with electrodes 9 on both sides for charge extraction. One of them is used as a direct hot terminal, and the other is used as a cold terminal via the case 8.

Further, an acoustic matching material 10 such as agar is brought into contact with the sound receiving surface of the piezoelectric material 7 that is seen through the opening of the metal case 8, and the tip surface of the acoustic matching material is made to protrude slightly from the front surface of the metal case 8. do.

The free surface of the acoustic matching material is covered with a resin sheet 11 to maintain the shape of the acoustic matching material 1° and to prevent the liquid (water, oil, etc.) contained therein from evaporating.

Modification 2 The present invention may be modified as follows.

That is, FIGS. 3A and 3B are cross-sectional views showing other embodiments of the microphone according to the present invention, in which the shape of the acoustic matching material is a concave lens 12 or a convex lens 13.

By doing so, it becomes possible to control the directivity of the ultrasonic transducer, and the sensitivity and S/N ratio can be improved.

However, forming the microphone sound-receiving surface into the above-mentioned shape can be easily realized because the acoustic matching material is generally a gelatinous material that can maintain a desired shape under no load, but it can be easily realized without significant deformation. The resin coating 11 to prevent
Needless to say, it may be made of a resin material having appropriate elasticity and flexibility.

(Effects of the Invention) Since the present invention is constructed as described above, it receives sound from an ultrasonic microphone positioned on the surface of a living body in order to achieve ultrasonic coupling with a temperature or pressure sensor implanted in the living body. The surface is highly flexible and has impedance matching with the biological surface, making it possible to adapt to the unevenness of the biological surface and increase the degree of adhesion, reducing acoustic loss and stabilizing under high S/N. It is extremely effective in making accurate measurements.

[Brief explanation of drawings]

Figure 1 [a] and (bl are respectively a plan view and a sectional view showing an embodiment of the present invention, and Figure 2 (al and (bl) are a principle diagram showing an implementation method of in-vivo temperature measurement and a conventional FIG. 3 is a cross-sectional view of a sonic 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.

Claims (2)

[Claims] (1) In order to detect the ultrasonic signal emitted by the sensor implanted in the living body on the surface of the living body, a highly elastic acoustic matching material is brought into contact with one side of the ultrasonic transducer, and the free surface of the acoustic matching material is protected. An ultrasonic microphone characterized by being coated with a membrane. (2) The ultrasonic microphone according to claim (1), wherein the free surface of the acoustic matching material has a lens-like structure.