Location

La Jolla, CA

Start Date

1981 12:00 AM

Description

The article describes the results of two methods: the Fresnel approximation and the convolution method used for the exact Rayleigh-Sommerfeld equation. Curves for the Fresnel approximation are shown as a function of flaw depth and number of sample points. Despite a violation of the fresnel condition, an image can be achieved without visible phase distortion. This and its limits are shown on synthetic and experimental data. By shifting the hologram and not changing the symmetric phase factor, calculation time is saved because the rearrangement in the image space is achieved automatically. The exact method "angular spectrum" has been simplified in three steps. For different insonification angles in shear wave holography, the data set must be multiplied by an aperture function before being Fourier transformed. Examples demonstrate the usefulness of contact technique probes. To improve the recording time, a 140 element array will be multiplexed electronically and moved mechanically.

Book Title

Proceedings of the ARPA/AFML Review of Progress in Quantitative NDE

Chapter

8. Ultrasonic Imaging and Microscope

Pages

203-207

Language

en

File Format

application/pdf

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Jan 1st, 12:00 AM

Advances in Computer Reconstruction of Acoustical Holography

La Jolla, CA

The article describes the results of two methods: the Fresnel approximation and the convolution method used for the exact Rayleigh-Sommerfeld equation. Curves for the Fresnel approximation are shown as a function of flaw depth and number of sample points. Despite a violation of the fresnel condition, an image can be achieved without visible phase distortion. This and its limits are shown on synthetic and experimental data. By shifting the hologram and not changing the symmetric phase factor, calculation time is saved because the rearrangement in the image space is achieved automatically. The exact method "angular spectrum" has been simplified in three steps. For different insonification angles in shear wave holography, the data set must be multiplied by an aperture function before being Fourier transformed. Examples demonstrate the usefulness of contact technique probes. To improve the recording time, a 140 element array will be multiplexed electronically and moved mechanically.