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BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a conventional ultrasonic
transducer, FIG. 2 is a diagram showing the receiving sensitivity of the ultrasonic transducer of
the prior art and the present invention, and the third in FIG. Fig. 4 is a perspective view of the
ultrasonic transducer, Fig. 4 is a top view thereof, Fig. 5 is a perspective view of another
embodiment of the present invention, and Fig. 6 is a top view thereof. 5... Curved frame, 6 .. .. °
hole, 7 ........ Piezoelectric polymer film, 8j 8 '..... Substrate, 9j 9' ..... Article.
DETAILED DESCRIPTION OF THE INVENTION The present invention provides an ultrasonic
transducer which is not subject to standing wave shadows # and does not result in
desensitization. A conventional ultrasonic transducer of this type will first be described with
reference to FIG. As shown in FIG. 1, a piezoelectric polymer film 1 is used. A conventional O
ultrasonic transducer having a structure in contact with a curved frame 2 has a radius of
curvature of about 4 to 5 mm. The radius of curvature of the curved surface O on which the film
of the frame 2 should be stretched when designed near the resonance frequency f40KIIz. ) And
46 ° following v-C7Ly-A2 V) When the opening angle θ is 2 °-, trr / '772 "; 1 or so, the base 3
of the base for fixing this frame 2 and the top of the curve of the film 1 A standing wave
generated at an interval 1 with 4 appears just in the use band of the ultrasonic transducer as
shown by the broken line in FIG. 2, whereby frequency customization in the use band may be
greatly degraded . In order to prevent this standing wave, a sound absorbing material such as
glass wool may be filled between the film 1 and the substrate 3 shown in FIG. 1, but acoustic
resistance is not added to the back of the film by the sound absorbing material. 2 As shown by
the dot-and-dash line in FIG. The present invention is intended to eliminate the disadvantages of
upper rice, and one embodiment of the present invention will be described below with reference
to FIGS. 3 and 4. In FIG. 3 and FIG. 4, reference numeral 5 denotes a curved frame having holes
6, and a piezoelectric polymer film 7 having electrodes formed on both sides is adhered to one
side of the curved frame 5v. The reference numeral 8 designates a substrate for mounting the
above-mentioned curved frame 5, and in the central part of this substrate 8'7E on one side
thereof, a projection 9 having a ridge of a cross-sectional scale is formed. The both end faces
parallel to the curved frame 50 are fixed to the surface end of the substrate 80. According to this
embodiment, the interval l 'between the upper surface of the ridge 9 of the substrate 8 and the
top 4' of the film 7 can be 4 mm or less, and the standing wave generated at one interval .beta. '
This occurs at a frequency higher than the use band of the Zeeser, and the characteristic shown
by the solid line in FIG. 2 becomes a characteristic that the frequency characteristic O
degradation as shown by the corner of the 21st corner does not occur. 5 and 6 show another
embodiment of the present invention. In this embodiment, a ridge 9 'having a semicircular cross
section is formed on a substrate 8', and an interval Irr is set to 4 mm or less I). The frequency
characteristic does not deteriorate even in the fifth embodiment. The present invention has the
above-described structure, and according to the present invention, it is possible to prevent the
occurrence of standing waves in the use band and to prevent the deterioration of the frequency
characteristics, and to provide a sound absorbing material. Since it is not used, the sensitivity
does not decrease.