Depth Analysis of Polymer-Coated Steel Samples Using Near-Infrared Femtosecond Laser Ablation Inductively Coupled Plasma Mass Spectrometry

Author(s): M. Paz Mateo, Carmen C. Garcia, R. Hergenröder

Abstract:

“The viability of near-infrared femtosecond laser ablation (fs-LA) inductively coupled plasma mass spectrometry (ICPMS) for the in-depth analysis of polymer coatings over galvanized steel substrates has been studied. A good depth resolution was obtained modifying the femtosecond Gaussian beam to a flat-top beam by using a liquid-crystal display. In order to avoid mixing of information coming from successive shots, a low repetition rate was accomplished and signals were monitored shot by shot. Different kinds of coatings were used to demonstrate the capability of femtosecond ablation for depth-profiling analysis. Ablation was conducted under He atmosphere, after sample cell Ar was admixed. The depth profiles obtained by LA-ICPMS are in good agreement with those obtained by GD-OES for the three analyzed samples. In cases where due to averaging over several millimeter sample roughness determines the depth resolution of GD-OES, it was found that LA-ICPMS achieves better depth resolution due to the better lateral resolution. The depth resolution obtained by LA-ICPMS was found to be 240 nm and 2.3 μm, for a hot-dip galvanized steel (HDGS) and a polymer−polymer-coated HDGS, respectively, compared to the 2.2 and 4.5 μm achieved with GD-OES for the same samples. ”

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Publication:Analytical Chemistry
Issue/Year: Anal. Chem., 2007, 79 (13), pp 4908–4914
DOI: 10.1021/ac070241q

A liquid crystal atmospheric turbulence simulator

Author(s): Lifa Hu, Li Xuan, Zhaoliang Cao, Quanquan Mu, Dayu Li, and Yonggang Liu

Abstract:

“In the paper, a method to calculate the time evolution turbulence wavefronts based on the covariance method is theoretically presented in detail. According to it, the time-evolution wavefronts disturbed by atmospheric turbulence were experimentally generated by our LC atmospheric turbulence simulator (ATS) based on liquid crystal on silicon (LCOS) with high pixel density, and measured with a wavefront sensor. The advantage of such a LC ATS over a conventional one is that it is flexible with considering the weather parameters of wind speed and Cn², and is relatively easy to control.”

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Publication: Optics Express
Issue/Year: Optics Express, Vol. 14, Issue 25, pp. 11911-11918 (2006)
DOI: 10.1364/OE.14.011911

Direct measurement of the skew angle of the Poynting vector in a helically phased beam

Author(s): Jonathan Leach, Stephen Keen, Miles J. Padgett, Christopher Saunter, and Gordon D. Love

Abstract:

“We measure the local skew angle of the Poynting vector within a helically-phased, exp (il φ), beam using a Shack Hartmann wavefront sensor. It is the skew angle of the Poynting vector with respect to the beam axis that gives rise to the orbital angular momentum of a light beam. We confirm that this skew angle is l/kr, corresponding to an orbital angular momentum of lћ per photon. Measurement of orbital angular momentum in this way is an alternative to interferometric techniques giving a non-ambiguous result to both the magnitude and sign of l from a single measurement, without any restriction on the optical bandwidth.”

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Publication: Optics Express
Issue/Year: Optics Express, Vol. 14, Issue 25, pp. 11919-11924 (2006)
DOI: 10.1364/OE.14.011919

Digital speckle shearing interferometer using a liquid-crystal spatial light modulator

Author(s): Shuai Zhao and Po Sheun Chung

Abstract:

“A digital speckle shearing interferometer is developed using a dynamic binary phase grating realized by an electrically addressed, twisted nematic liquid-crystal spatial light modulator as the shearing element. The standard phase-shifting algorithm can be easily achieved by changing the grating pattern displayed on the spatial light modulator. The method has a number of advantages including variable sensitivity, no moving part, and no requirement for calibration of the value of the phase shift. The error due to the unexpected diffraction order is also discussed. ”

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Publication: SPIE – Optical Engineering
Issue/Year: SPIE – Optical Engineering, Vol. 45, 105606 (2006);
DOI: 10.1117/1.2360940

Dynamisches System für die Aufnahme und optische Rekonstruktion von Hologrammen

Author(s): Günther Wernicke, Johannes Frank, Christian Günther, Sven Krüger

Abstract:

“Adressierbare räumliche Lichtmodulatoren mit einer möglichst idealen Phasenmodulation sind die Voraussetzung für deren Anwendung in der digitalen Holographie. Eine angepasste Treiberelektronik und eine genaue Kenntnis des Modulationsverhaltens kann zu einem dynamischen Phasenmodulations-System mit nahezu linearer Kennlinie und einem maximalen Phasenhub von 2 pi führen.
Ein System zur Aufnahme und Rekonstruktion von digitalen Hologrammen mit digitaler Bearbeitung der Hologrammdaten wird gezeigt. Daten von einer CCD-Kamera werden in den PC eingelesen und von diesem auf den Lichtmodulator gegeben. Damit wird ein Analog-Digital-Konverter (Hologrammaufnahme) und ein Digital-Analog-Konverter (optische Hologrammrekonstruktion) realisiert. Das Auflösungsvermögen wird diskutiert und Anwendungsmöglichkeiten, insbesondere durch Manipulationen am rekonstruierten Wellenfeld werden gezeigt.
Damit werden neue Anwendungen in der zerstörungsfreien holographischen Prüfung und in der holographischen Mikroskopie und der Kombination von beiden möglich. ”

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Publication: DGaO-Proceedings 2006
Issue/Year: DGaO-Proceedings 2006, 107. Tagung, Vortrag: B36,
ISSN: 1614-8436

Spiral interferogram analysis

Author(s): Alexander Jesacher, Severin Fürhapter, Stefan Bernet, and Monika Ritsch-Marte

Abstract:

“Interference microscopy using spatial Fourier filtering with a vortex phase element leads to interference fringes that are spirals rather than closed rings. Depressions and elevations in the optical thickness of the sample can be distinguished immediately by the sense of rotation of the spirals. This property allows an unambiguous reconstruction of the object’s phase profile from one single interferogram. We investigate the theoretical background of “spiral interferometry” and suggest various demodulation techniques based on the processing of one single interferogram or multiple interferograms.”

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Publication: Journal of the Optical Society of America A
Issue/Year: JOSA A, Vol. 23, Issue 6, pp. 1400-1409 (2006)
DOI: 10.1364/JOSAA.23.001400

Multipoint Holographic Optical Velocimetry in Microfluidic Systems

Author(s): R. Di Leonardo, J. Leach, H. Mushfique, J. M. Cooper, G. Ruocco, and M. J. Padgett

Abstract:

“We show how holographic optical trapping can be used for the multipoint measurement of fluid flow in microscopic geometries. An array of microprobes can be simultaneously trapped and used to map out the fluid flow in a microfluidic device. The optical traps are alternately turned on and off such that the probe particles are displaced by the flow of the surrounding fluid and then retrapped. The particles’ displacements are monitored by digital video microscopy and directly converted into velocity field values. This technique enables the measurement of a two-dimensional flow field at points arbitrarily distributed in a three-dimensional volume. The validity of the technique is demonstrated for the case of the flow around a spinning sphere and the flow at the outlet of a microchannel.”

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Publication: Physical Review Letters
Issue/Year: Phys. Rev. Lett. 96, 134502 (2006)
DOI: 10.1103/PhysRevLett.96.134502

Spiral interferometry

Author(s): Severin Fürhapter, Alexander Jesacher, Stefan Bernet, and Monika Ritsch-Marte

Abstract:

“We present a surprising modification of optical interferometry. A so-called spiral phase element in the beam path of a standard microscope results in an interferogram of phase samples, for which the interference fringes have the shape of spirals instead of closed contour lines as in traditional interferograms. This configuration overrides the basic problem of interferometry, i.e., that elevations and depressions cannot be distinguished. Therefore a complete sample profile can be reconstructed from a single exposure, promising, e.g., high-speed metrology with a single laser pulse. The method is easy to implement, it does not require a spatially separated reference beam, and it is optimally stable against environmental noise.”

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Publication: Optics Letters
Issue/Year: Optics Letters, Vol. 30, Issue 15, pp. 1953-1955 (2005)
DOI: 10.1364/OL.30.001953

Common-path interferometry with one-dimensional periodic filters

Author(s): Victor Arrizón and David Sánchez-de-la-Llave

Abstract:

“We discuss a spatial filtering interferometry setup that employs a periodic spatial filter with either cosine transmittance or binary phase modulation. The setup’s input plane is formed by two separate windows, one of which supports a phase object and the other, a reference beam. Using the appropriate frequency and orientation of the filter produces an interference pattern of the two input fields at the output plane of the system. The main attributes and advantages of the setup are discussed and experimentally illustrated with the example of a binary phase periodic filter implemented with a spatial light modulator.”

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Publication: Optics Letters
Issue/Year: Optics Letters, Vol. 29, Issue 2, pp. 141-143 (2004)
DOI: 10.1364/OL.29.000141

Optische Verarbeitung von interferometrischen Streifenbildern und die Fehlererkennung durch Wavelet-Filterung (Optical Processing of Interferometric Fringes and Detection of Faults by Wavelet Filtering)

Author(s): F. Kallmeyer, G. Wernicke, S. Krüger, H. Gruber, W. Osten, D. Kayser

Abstract:

“Das Erkennen und Klassifizieren von Fehlern ist eine wichtige Aufgabe der optischen zerstörungsfreien Materialprüfung in der industriellen Qualitätskontrolle. Eine Vielzahl von Daten über Fehler im Material sind in interferometrischen Streifenmustern enthalten. Diese Daten müssen für die weitere Auswertung reduziert werden. Eine Möglichkeit der Datenreduktion ist durch die Wavelet-Transformation gegeben. Fehler in interferometrischen Streifenmustern sollen durch Wavelet-Filter erkannt, lokalisiert und klassifiziert werden. Wavelet-Funktionen sind sowohl im Ortsraum als auch im Frequenzraum lokalisiert und eignen sich deshalb zur Extraktion von Merkmalen ohne Verlust der räumlichen Zuordnung. Eine Klassifizierung der Interferogramme ist möglich, da die Fehlerklassen charakteristische Eigenschaften haben, die mit bestimmten Klassen von Wavelet-Filtern erkannt werden können.

The detection and classification of faults is a major task for optical non-destructive testing in industrial quality control. Interferometric fringes contain a large amount of data with information about possible defect structures. These data must be reduced for further evaluation. One possible way is the filtering of the images by the adaptive wavelet transform. Faults in interferometric fringe patterns should be detected, localised, and classified by wavelet filters. Wavelet functions are localised in the spatial as well as in the frequency domain. Therefore both the extraction and the localisation of faults is possible by the application of wavelet filters. A classification of interferograms can be realised, because the fault classes have characteristics detectable with a given class of wavelet filters.”

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Publication: tm – Technisches Messen
Issue/Year: tm – Technisches Messen, Volume: 70, Issue: 2, Pages 66-70, 2003
DOI: 10.1524/teme.70.2.66.20110