EP0033751A1 - Ultra-Hochfrequenz verwendender Ultraschallwandler - Google Patents

Ultra-Hochfrequenz verwendender Ultraschallwandler Download PDF

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Publication number
EP0033751A1
EP0033751A1 EP19800100662 EP80100662A EP0033751A1 EP 0033751 A1 EP0033751 A1 EP 0033751A1 EP 19800100662 EP19800100662 EP 19800100662 EP 80100662 A EP80100662 A EP 80100662A EP 0033751 A1 EP0033751 A1 EP 0033751A1
Authority
EP
European Patent Office
Prior art keywords
lens
ultrasonic
acoustic wave
ultrasonic transducer
aperture
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
EP19800100662
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English (en)
French (fr)
Other versions
EP0033751B1 (de
Inventor
Hiroshi Kanda
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Hitachi Ltd
Original Assignee
Hitachi Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Hitachi Ltd filed Critical Hitachi Ltd
Priority to DE8080100662T priority Critical patent/DE3063803D1/de
Priority to EP19800100662 priority patent/EP0033751B1/de
Publication of EP0033751A1 publication Critical patent/EP0033751A1/de
Application granted granted Critical
Publication of EP0033751B1 publication Critical patent/EP0033751B1/de
Expired legal-status Critical Current

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    • G—PHYSICS
    • G10—MUSICAL INSTRUMENTS; ACOUSTICS
    • G10K—SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
    • G10K11/00—Methods or devices for transmitting, conducting or directing sound in general; Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
    • G10K11/18—Methods or devices for transmitting, conducting or directing sound
    • G10K11/26—Sound-focusing or directing, e.g. scanning
    • G10K11/30—Sound-focusing or directing, e.g. scanning using refraction, e.g. acoustic lenses

Definitions

  • the present invention relates to ultrasonic transducers for use with devices using high frequency acoustic radiation and more particularly to such transducers which are suitable for use in-acoustic microscopes.
  • Recent evolution of generation and detection of high frequency acoustic waves extending up to 1 GHz can afford to provide an acoustic wave length of about 1 micron under water, giving rise to availability of an acoustic microscope.
  • an acoustic wave beam of an extremely small size is produced which is projected on a target specimen and propagation loss of acoustic radiation due to reflection, scattering and penetrant attenuation at the target is detected to obtain information representative of elastic properties of the target.
  • propagation loss of acoustic radiation due to reflection, scattering and penetrant attenuation at the target is detected to obtain information representative of elastic properties of the target.
  • a surface of the specimen is scanned two-dimensionally with the focused acoustic wave beam and the perturbed energy is displayed on a cathode-ray tube in synchronism with the scanning.
  • a prior art ultrasonic transducer as shown in Fig. 1, directed to such a reduction has a cylindrical crystalline body 20 as an ultrasonic wave propagation medium of sapphire, for example, with one flat surface optically polished and opposite surface formed with a concaved recess 25.
  • An RF electric signal produced from an electric signal source 10 is applied to a piezoelectric film 15 which in turn transmits an RF acoustic wave in the form of a plane wave into the crystalline body 20.
  • the acoustic plane wave is focused at a given focal point F by means of a positive acoustical lens 40 formed at an interface between the arcuate recess 25 and an ultrasonic wave focusing medium 30, typically water.
  • a sufficiently small ratio between focal length and aperture size that is, a sufficiently small F-number of the lens can contribute to generation of the ultrasonic wave beam of a small size which approximates its wave length.
  • a sufficiently small ratio between focal length and aperture size that is, a sufficiently small F-number of the lens can contribute to generation of the ultrasonic wave beam of a small size which approximates its wave length.
  • a sufficiently small ratio between focal length and aperture size that is, a sufficiently small F-number of the lens can contribute to generation of the ultrasonic wave beam of a small size which approximates its wave length.
  • a sufficiently small ratio between focal length and aperture size that is, a sufficiently small F-number of the lens can contribute to generation of the ultrasonic wave beam of a small size which approximates its
  • R, C 1 and C 2 denote the radius of curvature of the concaved ultrasonic lens 40, the speed of sound in the.lens material and the speed of sound in the focusing medium, respectively.
  • the front-face focal length F is, and the back-face focal length F' is,
  • the lens effect can be determined by multiplying a sound pressure distribution on the back-face focal plane by a pupil function of the lens and subjecting the product to a two-dimensional Hankel transformation.
  • the sound pressure distribution lie on the back-face focal plane and that the sound pressure distribution on the back-face focal plane be of a uniform amplitude and phase of a plane wave or subject to a Gaussian distribution in respect of amplitude and phase of a plane wave.
  • Another amplitude distribution may also attain the focussing effect but it requires a great number of multi-lens systems for elimination of the lens aberration and is unpractical for industrial purposes.
  • a curve on the left of the ordinate axis represents a sound pressure distribution along the lens axis and curves on the right represent orientational distributions at distances in terms of normalized l by ⁇ o 2 / ⁇ , ⁇ being the wavelength of acoustic wave used.
  • the distance between the back-face focal plane of the lens and the piezoelectric film is reduced to an extent that no interference of ultrasonic wave occurs. While this second design has many applications in the range of MHz frequencies, it is almost unpractical in the range of GHz frequencies. Because with sapphire as a lens material, the ultrasonic wave at 1 GHz has a wavelength of about 11 ⁇ m and there needs preparation of an extremely thin lens. Therefore, the first design alone is practical.
  • the desirable lens aperture is 100 ⁇ m but a piezoelectric film of the corresponding 100 ⁇ m aperture is difficult to prepare and to handle and in addition, has a high impedance level for which the impedance matching is difficult at RF electric signal supplied.
  • the prior art measure has many difficulties for production of an ultrasonic . transducer since it requires an extensively elongated crystalline body and a piezoelectric film of a reduced aperture of the same size as a reduced lens aperture.
  • An object of the present invention is to provide an ultrasonic transducer using ultra high frequency wherein attenuation of the acoustic wave can'be minimized.
  • Another object of the invention is to provide an ultrasonic transducer which can yield a high resolution even with a piezoelectric element of a larger aperture than that of a lens.
  • the present invention is featured by an acoustic wave propagation medium having an axial length which is 1/N (N: odd number) of a Fresnel focal distance.
  • the present invention analyzed the sound pressure distribution to find, within the Fresnel focal point, axial points at which Gaussian-like distributions of sound pressure take place and which correspond to 1/N (N: odd number) of the Fresnel focal distance, and the present invention is based on this analytical result.
  • the present invention has made a mathematical approach to sound pressure distributions in the near field which are normally difficult to analyze to find that Gaussian-like sound pressure distributions pursuant to an optical lens theory take place within the Fresnel focal distance. It was then proven that a lens subject to such a sound pressure distribution which occurs at a back-face focal plane of the lens can yield a good focusing characteristic.
  • a Gaussian-like sound pressure distribution takes place at an axial point other than ⁇ o 2 / ⁇ point, for example, at point A3.
  • the present invention is based on the aforementioned analytical result and grounded on the fact that there are axial points within the Fresnel focal distance at which the Gaussian-like distribution takes place, that these points correspond to 1/N (N: odd number) of the Fresnel focal distance, and that the width of the Gaussian-like distribution to meet the present invention is 1/N of the aperture size of the piezoelectric element.
  • Fig. 5 schematically shows one embodiment of an ultrasonic transducer in accordance with teachings of the present invention.
  • a cylindrical crystalline body 150 serving as an acoustic wave propagation medium and made of such a material as sapphire or fused silica has one surface on which a piezoelectric element 145 is mounted and the opposite surface in which a concaved lens 155 is formed.
  • the portion of the crystal-water interface other than the lens aperture is applied with an absorbant 160 such as a plastic material of epoxy resion or a vinyl tape, thereby preventing the sidelobe being transmitted into the medium 170.
  • the other portion than the lens aperture is also tapered to prevent the transmission of the sidelobe into the medium 170 and to mitigate the multiple echo within the lens.
  • a piezoelectric film with an aperture size of 143 ⁇ m would be required which is very difficult to handle practically, and this film would have an impedance level of 1 K ⁇ .
  • the piezoelectric film of this embodiment is easy to match with a 50 ⁇ coaxial cable.
  • the present invention can offer the piezoelectric film of the aperture size which is easy to impedance-match with the electrical system and easy to handle, and the lens aperture size which is 1/(odd number) of the piezoelectric film aperture, thereby highly mitigating difficulties in lens design of the acoustic microscope.
EP19800100662 1980-02-08 1980-02-08 Ultra-Hochfrequenz verwendender Ultraschallwandler Expired EP0033751B1 (de)

Priority Applications (2)

Application Number Priority Date Filing Date Title
DE8080100662T DE3063803D1 (en) 1980-02-08 1980-02-08 Ultrasonic transducer using ultra high frequency
EP19800100662 EP0033751B1 (de) 1980-02-08 1980-02-08 Ultra-Hochfrequenz verwendender Ultraschallwandler

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
EP19800100662 EP0033751B1 (de) 1980-02-08 1980-02-08 Ultra-Hochfrequenz verwendender Ultraschallwandler

Publications (2)

Publication Number Publication Date
EP0033751A1 true EP0033751A1 (de) 1981-08-19
EP0033751B1 EP0033751B1 (de) 1983-06-22

Family

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Family Applications (1)

Application Number Title Priority Date Filing Date
EP19800100662 Expired EP0033751B1 (de) 1980-02-08 1980-02-08 Ultra-Hochfrequenz verwendender Ultraschallwandler

Country Status (2)

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EP (1) EP0033751B1 (de)
DE (1) DE3063803D1 (de)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3718972A1 (de) * 1986-06-06 1987-12-17 Olympus Optical Co Akustische linse fuer schallmikroskope
EP0272154A2 (de) * 1986-12-19 1988-06-22 Xerox Corporation Akustische Druckköpfe
CN111112037A (zh) * 2020-01-20 2020-05-08 重庆医科大学 透镜式多频聚焦超声换能器、换能系统及其声焦域轴向长度的确定方法

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2261527A1 (de) * 1974-02-15 1975-09-12 American Optical Corp
US3958559A (en) * 1974-10-16 1976-05-25 New York Institute Of Technology Ultrasonic transducer

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2261527A1 (de) * 1974-02-15 1975-09-12 American Optical Corp
US3958559A (en) * 1974-10-16 1976-05-25 New York Institute Of Technology Ultrasonic transducer

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
PROCEEDINGS OF THE IEEE, Vol. 67, No. 8, August 1979, pages 1092-1114 New York, U.S.A. C.F. QUATE et al.: "Acoustic Microscopy with Mechanical Scanning - A review" * Page 1094, column 1, line 11 - column 2, line 5; page 1102, column 2, line 14 - page 1105, column 1, line 29 * *

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3718972A1 (de) * 1986-06-06 1987-12-17 Olympus Optical Co Akustische linse fuer schallmikroskope
EP0272154A2 (de) * 1986-12-19 1988-06-22 Xerox Corporation Akustische Druckköpfe
EP0272154A3 (en) * 1986-12-19 1989-10-18 Xerox Corporation Acoustic printheads
CN111112037A (zh) * 2020-01-20 2020-05-08 重庆医科大学 透镜式多频聚焦超声换能器、换能系统及其声焦域轴向长度的确定方法

Also Published As

Publication number Publication date
DE3063803D1 (en) 1983-07-28
EP0033751B1 (de) 1983-06-22

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