An Investigation of the Limitations to the Maximum Attainable Sensitivity in Acoustical Image Converters

Jacobs, John E.; Berger, H.; Collis, W.J.

doi:10.1109/t-ue.1963.29308

Cited by 21 publications

(5 citation statements)

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“…Several types of image converter based on this principle have been developed (Semenikov 1958, Freitag et al 1960, Smyth et al 1963and Jacobs et al 1963. The performance of such devices has been summarized by Jacobs (1968).…”

Section: Continuous-wave Techniquesmentioning

confidence: 99%

The medical applications of ultrasonics

Wells

1970

Rep. Prog. Phys.

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2. Fundamental physics . 3. Transducers . 3.1. Transducer materials . 3.2. Transducer design . 4.1. Beam formation . 4.2. Methods of measurement . 5.1. Propagation velocity . . 5.2. Characteristic impedance . 5.3. Absorption . 6.1. Early investigations . 6.2. Thermal effects . 6.3. Mechanical effects . 6.4. Other investigations . 7. Surgical applications . 7.1. Neurosurgery . 7.2. Vestibular surgery . 8. Therapeutic applications . 8.1. Physiotherapy . 8.2. Production of aerosols . 9. Diagnostic applications . 9.1. Pulse-echo techniques . 9.2. Continuous-wave techniques . Appendix: glossary of biomedical terms . References . 4. The ultrasonic field . 5. Acoustic properties of biological tissues . 6. Interactions of ultrasonic waves with biological tissues

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Section: Continuous-wave Techniquesmentioning

confidence: 99%

The medical applications of ultrasonics

Wells

1970

Rep. Prog. Phys.

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“…Following specifically those rays which are refracted at the Rayleigh critical angle R , they proceed in a converging truncated cone of rays to intersect the specimen surface (3) where they intersect it to form the entry circle shown in the lower part of the figure. Those rays at and around R then mode convert to surface waves and propagates on a circle diameter to the far side (4), where they reconvert and proceed back to the lens (5) and the piezoelectric element (6). For a buffer rod of length L, a lens of radius R C , focusing at an axial distance Z 2 , where it is defocused to axial distances Z A and Z B ; the time t 1 required for the directly reflected pulse following the ray path on the lens axis of symmetry to travel from the piezoelectric element and return for Z is…”

Section: Surface Wave Amplitudementioning

confidence: 99%

“…The spot diameter E R can be calculated from the amplitude point spread function of the double cylindrical lens system placed on the entry surface by the entry circle. The point spread function produced by a cylindrical lens has been shown by Born and Wolf [6] and Kino [7] to be of the form (sin X/X) 2 , where X has the same definition as equation (7) and figure 8, for a pulseecho system. Gilmore et al [12] used these results to calculate the −3 dB and −1 dB diameters for the point spread function for the crossing zone at the entry circle centre:…”

Section: Surface Wave Amplitudementioning

confidence: 99%

“…Dunn proposes scanned ultrasonic testing absorbtion microscope [5]. 1963 Jacobs adds electron multiplier to Sokolov Tube [6]. 1966 Korpel et al at Zenith Corp. invent scanning laser acoustic microscope [7].…”

mentioning

confidence: 99%

“…In 1963 Jacobs et al [6] added an electron multiplier to the Sokolov Tube for a factor of ten increase in signal strength. Even then Sokolov Tube images showed poor resolution and contrast in comparison to the ultrasonic Cscan images that were being developed during the same period, but they had the advantage of providing a realtime image.…”

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confidence: 99%

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Industrial ultrasonic imaging and microscopy

Gilmore¹

1996

J. Phys. D: Appl. Phys.

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Ultrasonic imaging and scanned acoustic microscopy are terms used to describe similar imaging processes at different magnifications and frequencies. Both processes form images by acquiring spatially correlated measurements of the interaction of high-frequency sound waves with materials. With the exception of the interference measurement, called V (z ), and the gigahertz frequencies used by the higher frequency scanning acoustic microscopes, it is difficult to establish operational differences between them. This is especially true since almost all commercial ultrasonic imaging systems use transducers producing focused beams and can display magnified high-resolution images.Ultrasonic C-scan imaging was developed largely by the ultrasonic nondestructive testing industry. The development was gradual and evolutionary. Over a 50-year period, better and better broadband transducers, electronics and scanners were developed for operation at progressively higher frequencies, now ranging from 1.0 to 100 MHz. Conversely, scanning acoustic microscopes made a relatively sudden appearance 20 years ago on the campus of Stanford University. The first scanning acoustic microscopes operated at gigahertz frequencies and used microwave electronics that produced acoustic tone bursts with many wavelengths per pulse.Three factors control resolution in an acoustic image:• diameter of the acoustic beam or its point spread function (PSF);• size and spacing of the pixels making up the image;• signal-to-noise ratio (contrast) of the feature being resolved.The beam diameter, or PSF, is controlled by the frequency of the ultrasonic pulse and the focal convergence of the beam (or focal length to diameter ratio Z /d ). In the coupling fluid, the Z /d ratio is determined by the transducer diameter and lens, but in the material, Z /d is established by the materials ultrasonic velocities. Pixels are the squares of colour or greyscale that make up computer displays of scanned images. Following Nyquist's criterion, the resolution of those images is twice the size and spacing of the pixels. It follows, therefore, that in order to support the resolution of an ultrasonic beam, the pixels must be no larger than half that beam diameter. Finally, the contrast of the feature being studied must be (at least) a clear shade of grey above the background produced by the image noise. The noise can be due to the material or the electronics.Written to support industrial ultrasonic inspection of materials, this discussion will emphasise the similarities between imaging and microscopy rather than the differences. The roles of the focusing lens, the pulse frequency, and the material being imaged, with respect to the final resolution of an acoustic image, will be considered in detail. It will be shown that additional improvements in resolution can be achieved with image processing. Finally, applications studies in metals, ceramics, composites, attachment methods, coatings, and electronic assemblies will be used to demonstrate specific roles for imaging/microscopy in no...

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A Survey of Ultrasonic Image Detection Methods

Berger

1969

Acoustical Holography

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An Investigation of the Limitations to the Maximum Attainable Sensitivity in Acoustical Image Converters

Cited by 21 publications

References 0 publications

The medical applications of ultrasonics

The medical applications of ultrasonics

Industrial ultrasonic imaging and microscopy

A Survey of Ultrasonic Image Detection Methods

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