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| Content Provider | IEEE Xplore Digital Library |
|---|---|
| Author | Balogun, O. Pratt, N. Murray, T.W. |
| Copyright Year | 2005 |
| Description | Author affiliation: Dept. of Aerosp. & Mech. Eng., Boston Univ., MA, USA (Balogun, O.; Pratt, N.; Murray, T.W.) |
| Abstract | Conventional laser ultrasonic systems use pulsed laser sources to generate broadband acoustic waves. The theoretical signal to noise ratio (SNR) of these systems, in the shot noise limit, is inversely proportional to the square root of the bandwidth of the detection system. Previous researchers have shown that improvements in the SNR can be made by generating narrowband acoustic signals using temporally and/or spatially modulated laser pulses, and reducing the detection bandwidth accordingly. The paper describes the generation of high frequency acoustic waves using an amplitude modulated continuous wave (CW) laser. The acoustic signals are detected using a path stabilized Michelson interferometer coupled to an RF lock-in amplifier. This allows for control of the detection bandwidth, which can be reduced by several orders of magnitude below typical broadband laser ultrasonic systems. Experimental results are given showing CW generated acoustic waves in various material systems. The magnitude and phase of the acoustic signals in the frequency domain are detected by the interferometer/lock-in amplifier system, and these data are in turn processed to synthesize the time domain response. The use of narrowband generation/detection combined with subsequent time domain reconstruction allows for a large increase in SNR without losing the ability to distinguish individual acoustic arrivals or modes in the time domain. |
| Starting Page | 48 |
| Ending Page | 51 |
| File Size | 641764 |
| Page Count | 4 |
| File Format | |
| ISBN | 0780384121 |
| ISSN | 10510117 |
| DOI | 10.1109/ULTSYM.2004.1417665 |
| Language | English |
| Publisher | Institute of Electrical and Electronics Engineers, Inc. (IEEE) |
| Publisher Date | 2004-08-23 |
| Publisher Place | Canada |
| Access Restriction | Subscribed |
| Rights Holder | Institute of Electrical and Electronics Engineers, Inc. (IEEE) |
| Subject Keyword | Laser noise Acoustic signal detection Optical pulse generation Signal to noise ratio Laser theory Acoustic pulses Acoustic waves Bandwidth Acoustic noise Narrowband |
| Content Type | Text |
| Resource Type | Article |
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