| Project/Area Number |
01460163
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| Research Category |
Grant-in-Aid for General Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Research Field |
計測・制御工学
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| Research Institution | Sizuoka University (1990)
Kyoto Institute of Technology (1989) |
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Principal Investigator |
MIYASHITA Toyokatsu Shizuoka University, Research Institute of Electronics, Professor, 電子工学研究所, 教授 (00026238)
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| Co-Investigator(Kenkyū-buntansha) |
NAKAYAMA Jun-ichi Kyoto Institute of Technology, Dept. Electronics, Assoc. Professor, 工芸学部, 助教授 (40093356)
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| Project Period (FY) |
1989 – 1990
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| Project Status |
Completed (Fiscal Year 1990)
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| Budget Amount *help |
¥4,500,000 (Direct Cost: ¥4,500,000)
Fiscal Year 1990: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 1989: ¥4,000,000 (Direct Cost: ¥4,000,000)
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| Keywords | Holographic Imaging / Multifrequency Method / 3-Dimensional Imaging / Ultrasonic Imaging / High Resolution / Medical Imaging |
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| Research Abstract |
Multifrequency holographic imaging method uses a two-dimensional spatial receiver (or transmitter) array for lateral two-dimensional resolution and a frequency array for range resolution to get a true three-dimensional resolution.
First, we made a variety of computer simulations of three dimensional multifrequency holographic imaging, and confirmed that this method gives us a desirable true three dimensional resolution of the reconstructed images. That is, not only lateral but also range resolutions are both about 3.7 times wavelength of the central frequency of the frequency array.
We designed and ordered two-dimensional acoustic transducer array to Nippon Denpa Kogyo Company Limited. Front size of the transducer is 80 mm times 80 mm. A large PZT plate of a good quality is cemented on the backing block made of Epoxy resin and metallic powder. Cutting it by a so-called diamond cutter, we made 16 times 16 (=256) receiver transducer elements of a small aperture of 1.0 mm times 1.0 mm, whos
… More
e spacing is 4.5 mm. Rest part of the pzt material is also composed of many small fragments of transducers. Those were connected electrically parallel to make a big size of transmitting acoustic transducer of 80 mm times 80 mm. This type of transducer structure is guaranteed to make a uniform piston oscillation and to transmit an ideal parallel plane wave to the object. Resonance frequency was designed to 600 KHz, and the frequency aperture of multifrequency hologram is designed from 450 KHz to 550 KHz. Therefore, sensitivity or gain and phase characteristics over this frequency range is very uniform and also mutual coupling between the adjacent elements is very small, i. e. -60 dB. These characteristics are very important for multifrequency holographic imaging of synthetic aperture method.
Introducing a direct frequency synthesizer of a fast response, we modified the conventional control circuit of holographic measurement, and made it possible to measure multifrequency hologram in a desirable short time. i. e. 32 ms per frame, being directly controlled by a software of a minicomputer. This speed is necessary for medical imaging of living body.
We designed and fabricated multi-channel preamplifiers for every receiver elements and simultaneously digitizing circuits for each raw of the matrix to make the measurement as fast as possible. Less
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