Communications – electrical: acoustic wave systems and devices – Signal transducers – Underwater type
Patent
1988-10-18
1989-11-14
Steinberger, Brian S.
Communications, electrical: acoustic wave systems and devices
Signal transducers
Underwater type
310336, H04R 102
Patent
active
048812129
DESCRIPTION:
BRIEF SUMMARY
(TECHNICAL FIELD)
This invention is basically an improved broadband ultrasonic transducer designed for medical or industrial applications. More specifically, it is an ultrasonic transducer with better acoustic impedance matching between an ultrasonic oscillator and the surface of a subject.
(BACKGROUND ART)
FIG. 6 is a sectional view of a conventional ultrasonic transducer configuration (prior art). In the figure, number 1 indicates an ultrasonic oscillator, 2 indicates an acoustic impedance matching member installed in front, 3 indicates an acoustic damper, and 4 indicates the subject.
Conventionally, a member having a thickness equivalent to a single or three-layer quarter-wavelength plate is used for acoustic impedance matching layer 2. The energy transmission efficiency and bandwidth are both improved when the number of quarter wavelength plates and the acoustic impedance of the material are properly selected. It is also known, however, that an acoustic impedance matching layer consisting of n layer of a quarter-wavelength plate fails to obtain a major additive effect as compared to when n=2 if n is made n>or=3.
Therefore, an improved version of acoustic impedance matching layer 2 is proposed (as noted in published Patent No. Showa 58-18095) that successively changes the acoustic impedance between the respective layers in contact with ultrasonic oscillator 1 and the surface of the subject. However, it is not easy to actually. produce a composite material having a gradually changing acoustic impedance, or if produced, a lack of reproducibility poses a problem.
(DISCLOSURE OF THE INVENTION)
The object of this invention is to provide a ultrasonic transducer that better matches the ultrasonic oscillator with a subject by providing an acoustic matching layer of good reproducibility that gradually changes acoustic impedance.
(METHOD OF SOLVING THE PROBLEM)
To use our invention in the preferred application mode, we employed an ultrasonic transducer, consisting of an ultrasonic oscillator and an impedance matching member installed on the ultrasonic radiation surface, characterized by the impedance matching member having a multilayer configuration of unit layers, each thinner than a quarter-wavelength. Each unit layer also has a laminated structure consisting of heavy metal and plastic layers with their layer thickness factor being set to increase gradually in order from the unit layer in contact with the ultrasonic oscillator to the other unit layer in contact with the subject.
(BRIEF DESCRIPTIONS OF DRAWINGS)
FIG. 1 is the schematic sectional view of the preferred application mode of the ultrasonic transducer based on this invention.
FIGS. 2 and 3 are sectional views of individual unit layers that make up the acoustic impedance matching member shown in FIG. 1.
FIGS. 4 and 5 show the acoustic equivalent circuit of the acoustic impedance matching member shown in FIG. 1.
FIG. 6 shows the schematic sectional view of a conventional ultrasonic transducer (prior art).
(BEST MODE FOR CARRYING OUT THE INVENTION)
An example of the preferred application mode of this invention is described as follows in detail by referring to the drawings.
In FIG. 1, number 1 indicates an ultrasonic oscillator consisting of PZT and other components, 2 indicates an acoustic impedance matching member (that characterizes this invention) installed in front of ultrasonic oscillator 1 (ultrasonic wave radiation surface), 3 indicates an acoustic damper installed on back of ultrasonic oscillator 1, and 4 indicates the subject. Acoustic impedance matching member 2 consists of the 21, 22, . . . 2n laminated unit layers, each of which is thinner than a quarter-wavelength (for example, approx. lambda/10 to 20) and laminated to each other using a normal application of adhesion or heat adhesion. FIGS. 2 and 3 are sectional views showing more detailed configuration of each unit layer that makes up the acoustic impedance matching member. FIG. 2 shows the layers close to the end in contact with ultrasonic oscillator 1, and FIG. 3 shows
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Kojima Moonray
Steinberger Brian S.
Yokogawa Medical Systems Limited
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