| Download | - View accepted manuscript: Hadamard multiplexing in laser ultrasonics (PDF, 6.8 MiB)
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| DOI | Resolve DOI: https://doi.org/10.1364/OE.20.025798 |
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| Author | Search for: Rousseau, Guy1; Search for: Blouin, Alain1 |
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| Affiliation | - National Research Council of Canada. Energy, Mining and Environment
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| Format | Text, Article |
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| Subject | Hadamard multiplexing; Laser intensities; Laser ultrasonics; Non-contact ultrasonic inspection; Pulse echoes; Shot-noise level; Signaltonoise ratio (SNR); Spatial intensity distribution; Surface damages; Synthetic aperture focusing techniques; Chemical detection; Detectors; Laser beams; Shot noise; Signal detection; Signal to noise ratio |
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| Abstract | In state-of-the-art laser ultrasonics (LU), the signal-to-noise ratio (SNR) is limited by the shot noise of the detected laser radiation. Further improving the SNR then requires averaging multiple signals or increasing generation and/or detection laser intensities. The former strategy is time consuming and the latter leads to surface damages. For signal-independent limiting noises, Hadamard multiplexing increases the SNR by averaging multiple signals in parallel using a single detector. Here we consider the use of Hadamard multiplexing in LU for the non-contact ultrasonic inspection of materials. By using 31 element Hadamard masks to modulate the spatial intensity distribution of the generation laser beam, the measured SNR is improved by a factor 2.8, in good agreement with the expected multiplexing or Fellgett advantage. In contrast to many other applications of Hadamard multiplexing, the SNR is improved for shot-noise-limited measurements since the shot noise level is independent of the signal in LU. The Hadamard multiplexing of the detection laser beam is also considered but can only lead to a throughput or Jacquinot advantage. However, for pulse-echo LU, the Hadamard multiplexing of both generation and detection laser beams allows using the synthetic aperture focusing technique (SAFT). |
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| Publication date | 2012-10-31 |
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| In | |
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| Language | English |
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| Peer reviewed | Yes |
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| NRC number | NRC-EME-53217 |
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| NPARC number | 21270150 |
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| Export citation | Export as RIS |
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| Report a correction | Report a correction (opens in a new tab) |
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| Record identifier | 1e4b6963-fcf6-4392-af16-a95c1e21310e |
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| Record created | 2014-01-06 |
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| Record modified | 2020-06-04 |
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