Event Title

Improved Performance of Laser-Ultrasonic F-SAFT Imaging

Location

Snowbird, UT, USA

Start Date

1-1-1999 12:00 AM

Description

The spatial resolution of laser-ultrasonics depends upon the spot sizes of the generation and detection lasers and may be inadequate for detecting small and buried flaws. The use of a broad laser spot at the surface of the specimen to produce an ultrasonic beam with little divergence gives a spatial resolution limited by the spot size. In the opposite case, focusing the laser beam to a small laser spot yields a strongly diverging acoustic wave, leading also to poor spatial resolution. As in conventional ultrasonics, spatial resolution can be greatly enhanced by the use of the Synthetic Aperture Focusing Technique (SAFT) [1,2]. In addition, the coherent summation performed by SAFT yields an improved signal-to-noise ratio (SNR). Originally developed in the time domain, SAFT can be advantageously implemented in the frequency domain (F-SAFT). F-SAFT is based on the angular spectrum approach [2–4], which allows a significant reduction in processing time as compared to time-domain SAFT.

Book Title

Review of Progress in Quantitative Nondestructive Evaluation

Volume

18A

Chapter

Chapter 1: Elastic Waves and Ultrasonic Techniques

Section

Laser Ultrasonics and Applications

Pages

309-316

DOI

10.1007/978-1-4615-4791-4_38

Language

en

File Format

application/pdf

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Jan 1st, 12:00 AM

Improved Performance of Laser-Ultrasonic F-SAFT Imaging

Snowbird, UT, USA

The spatial resolution of laser-ultrasonics depends upon the spot sizes of the generation and detection lasers and may be inadequate for detecting small and buried flaws. The use of a broad laser spot at the surface of the specimen to produce an ultrasonic beam with little divergence gives a spatial resolution limited by the spot size. In the opposite case, focusing the laser beam to a small laser spot yields a strongly diverging acoustic wave, leading also to poor spatial resolution. As in conventional ultrasonics, spatial resolution can be greatly enhanced by the use of the Synthetic Aperture Focusing Technique (SAFT) [1,2]. In addition, the coherent summation performed by SAFT yields an improved signal-to-noise ratio (SNR). Originally developed in the time domain, SAFT can be advantageously implemented in the frequency domain (F-SAFT). F-SAFT is based on the angular spectrum approach [2–4], which allows a significant reduction in processing time as compared to time-domain SAFT.