Optical Detection of Transient Lamb Waves on Rough Surfaces by a Phase-Conjugate Method

Matsuda, Youichi; Nakano, H.; Nagai, Satoshi

doi:10.1143/jjap.31.l987

Cited by 20 publications

(10 citation statements)

References 10 publications

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“…Nevertheless, this embodiment also requires active Iength stabilization. Another dass of LBU receivers use a "compensated" interferometer which removes the speckles deleterious effect by wavefront matehing [4][5][6][7][8][9][10][11][12]. The matehing is accomplished by using phase conjugation or beam cleanup.…”

Section: Theory Background On Laser-based Ultrasound Detectionmentioning

confidence: 99%

Robust Laser-Based Ultrasound Sensor Using Integrated Photo-Induced EMF Detection and Time-Delay Interferometer

Dunning

Pepper

Chiao

et al. 1997

Review of Progress in Quantitative Nondestructive Evaluation

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INTRODUCTIONThe important benefits of quantitative nondestructive evaluation can be realized by a manufacturer if the system is fully compatible with the manufacturing environment and cost effective. In many cases an in-line real-time process control would be desirable. There have been a variety of uhrasonie inspection techniques which have successfully met the aforementioned conditions. These techniques are able to capitalize on a !arge body of established ultrasonic methods and signal analysis. However, there are environments and processes which cannot use these conventional procedures because they require the partunder inspection to be either in physical contact with the transducer, via an epoxy, gel or fluid couplant, or maintained in close proxirnity to the transducers. These requirements may not be compatible with processes in which the part is at elevated temperatures, incompatible with the fluid couplant, physically remote or moving in a manner which adversely effects the required spacing. We present a robust uhrasonie technique which can work in these environments utilizing a laser-based uhrasound sensor incorporating photoinduced emf detection and a time-delay interferometer.Laser Based Ultrasound (LBU) with its inherent long stand-off distance for the generation and reception of the uhrasonie signals, offers a means to circumvent many manufacturing constraints. Several advantages to using a laser-based approach for the reception and detection of uhrasound are mentioned in the ensuing paragraph. The standoff distance between the parts being interrogated and the Iaser exciter and receiver can be several meters. These systems can operate with high spatial resolution on irregular and rough cut machined surfaces made from a variety of materials. The uhrasound launched within the material is normal to the surface even if the Iaser excitation is incident at a non-normal angle. For many parts, a LBU system can be configured to map out the region of interest in significantly less time than a conventional squirter system. The ability to generate short and focused Iaser pulses facilitates the generation of high bandwidth uhrasonie pulses. The Iaser receiver's high fractional bandwidth enables signal analysis using the full spectral content. The Iaser can be precisely located which can Iead to high spatial resolution. With all of theses advantages, however, LBU systems have yet to make a major impact in the commercial arena because of the issues of cost effectiveness coupled with the physical constraints imposed by many manufacturing environments. We will present a laser-based detector and system which effectively addresses both of these issues.Review of Progress m Quanl!tatlve Nondestrucllve Eva/uatwn.

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Section: Theory Background On Laser-based Ultrasound Detectionmentioning

confidence: 99%

Robust Laser-Based Ultrasound Sensor Using Integrated Photo-Induced EMF Detection and Time-Delay Interferometer

Dunning

Pepper

Chiao

et al. 1997

Review of Progress in Quantitative Nondestructive Evaluation

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show abstract

“…In several situations of practical interest, the proposed method, based on a referenceless speckle configuration, could provide additional information in comparison with conventional interferometers that use a reference beam. [4][5][6][7][8][9] The physics of the photo-EMF detector has been described in detail elsewhere. 10 In general, this detector is made by a photoconductive sample with two parallel stripe electrodes deposited on its front face ͑see Fig.…”

Section: Introductionmentioning

confidence: 99%

Detection of in-plane components of laser-induced ultrasound in adaptive optical speckle configuration

1999

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The optical detection of the in-plane displacements on a scattering aluminum metal sample, produced by laser-induced ultrasound, is reported. The experiments were performed with a GaAs adaptive photodetector operating at ϭ532 nm using a speckle-based referenceless configuration. In-plane displacements produced by shear and longitudinal ultrasound waves were observed and the estimations of their propagation velocities correspond well to the known data.

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“…In principle, these schemes circumvent the need for expensive electro-mechanicaj control elements as well as the need for high-quality optical components. For example, nonlinear optical phase conjugation techniques [4] have been applied to laser ultrasonic optical probing systems [5,6] to compensate for surface roughness (in the form of speckle), which would otherwise require one to select a small number of speckles to perform the detection -at a significant loss in sensitivity, on the order of 30 dB. In these compensation demonstrations, a double-pass geometry was employed whereby a probe beam first illuminated the workpiece, with the scattered light directed onto a phase-conjugate mirror, PCM.…”

Section: Introductionmentioning

confidence: 99%

“…The PCM generates a wavefrontreversed, or "time-reversed," replica of the beam [4], which, after striking the workpiece once again, emerges on its return path with its incident wavefront restored, yet with the desired phase modulation preserved, as imposed by the high-frequency ultrasonic surface displacement of the workpiece. Systems were demonstrated using externally pumped [5] as well as self-pumped [6] PCM's, both with good signal-to-noise performance. However, these systems require a doublepassing of the workpiece and, moreover, require collection of all the scattered light for perfect wavefront reconstruction.…”

Section: Introductionmentioning

confidence: 99%

Materials inspection and process control using compensated laser ultrasound evaluation (CLUE): demonstration of a low-cost laser ultrasonic sensor

Pepper¹,

Dunning²,

Mitchell³

et al. 1996

Lasers as Tools for Manufacturing of Durable Goods and Microelectronics

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We demonstrate the use of a nonsteady-state photo-inducedemf adaptive photodetector as a robust, low-cost laser ultrasonic sensor. This class of sensor enables high-fractional bandwidth ultrasound detection and, in addition, all-optical compensation of adverse in-factory noise, including vibration, speckle, relative platform motion, and optical fiber modal dispersion. Reference-beam and fiber-based time-delay interferometric configurations were demonstrated, as well as the ue of a diode laser as a compact optical probe. IntroductionThere is a great need in the manufacturing, aerospace (e.g., critical components, aging aircrafi), commercial, energy, automotive, microelectronics and DoD communities for diagnostic systems that can improve the efficiency, yield, and performance of various (laser-based) material processing operations -while reducing cost, labor, scrap, and machine downtime. Such needs

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Optical Detection of Transient Lamb Waves on Rough Surfaces by a Phase-Conjugate Method

Cited by 20 publications

References 10 publications

Robust Laser-Based Ultrasound Sensor Using Integrated Photo-Induced EMF Detection and Time-Delay Interferometer

Robust Laser-Based Ultrasound Sensor Using Integrated Photo-Induced EMF Detection and Time-Delay Interferometer

Detection of in-plane components of laser-induced ultrasound in adaptive optical speckle configuration

Materials inspection and process control using compensated laser ultrasound evaluation (CLUE): demonstration of a low-cost laser ultrasonic sensor

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