In the present study, a historical set of Late Roman glasses coming from a recently unearthed graveyard located in the small city of Cubas de la Sagra, within the Madrid region (Spain) was compositionally analysed using different techniques such as ultraviolet-visible (UV-Vis) and laser induced fluorescence (LIF) spectroscopies, X-ray fluorescence (XRF) and laser induced breakdown spectroscopy (LIBS). LIBS results, recorded upon nanosecond (ns) and femtosecond (fs) laser irradiation, served for identification of major glass components (to classify them into main historical glass groups) and of minor components (e.g. chromophores, decolouring agents and degradation products). Quantitative information regarding these components was obtained on the basis of calibration curves obtained using glass certified standards and local standards. We have demonstrated that LIBS serves for the noninvasive/micro-destructive, quantitative chemical characterization of most of the analysed historical glasses. Furthermore, this work establishes a comparison between LIBS analysis of glasses in the ns and fs regimes on one hand, and on the other hand with the results obtained 2 using XRF. The procedures and protocols here proposed can be applied for in-situ study of historical glass collections, regardless of their size, provenance and chronology.

No abstract

No abstract

Wavelength scanning interferometry and swept-source optical coherence tomography require accurate measurement of time-varying laser wavenumber changes. We describe here a method based on recording interferograms of multiple wedges to provide simultaneously high wavenumber resolution and immunity to the ambiguities caused by large wavenumber jumps. All the data required to compute a wavenumber shift are provided in a single image, thereby allowing dynamic wavenumber monitoring. In addition, loss of coherence of the laser light is detected automatically. The paper gives details of the analysis algorithms that are based on phase detection by a two-dimensional Fourier transform method followed by temporal phase unwrapping and correction for optical dispersion in the wedges. A simple but robust method to determine the wedge thicknesses, which allows the use of low-cost optical components, is also described. The method is illustrated with experimental data from a Ti:sapphire tunable laser, including independent wavenumber measurements with a commercial wavemeter. A root mean square (rms) difference in measured wavenumber shift between the two of ~4 m⁻¹ has been achieved, equivalent to an rms wavelength shift error of ~0.4 pm.

No abstract

The introduction of a pulsed laser into an electronic speckle-shearing pattern interferometer allows high-speed transient deformations to be measured. We report on a computerized system that permits automatic data reduction by introducing carrier fringes through the translation of a diverging lens. The quantitative determination of the phase map that is due to deformation is carried out by the spatial synchronous detection method. Experimental results obtained for a metal plate transiently deformed by an electromagnetic hammer illustrate the advantages of the proposed system.

A novel sensing method is proposed for wavelength scanning interferometry using multiple tunable light sources. As it is well known, a deterioration of depth resolution usually occurs when multiple phase intervals, corresponding to the multiple tunable light sources, are used for distance measurement purposes. It is shown here, that it is possible to regain depth resolution characteristics of a complete scan by means of a temporal phase unwrapping extrapolation method. With the proposed method, the resulting phase differences among multiple phase intervals can be successfully unwrapped to find out the intermediate phase. This effectively allows the application of whole-scan phase sensing for distance measurement using reduced scanning intervals, increased speed, and improved depth detection.

In this work we analyze the frequency response, the spatial distribution and continuity of the recovered phase in Lateral Shearing Interferometry (LSI). This frequency content and topology of the recovered phase is analyzed for the forward LSI operator as well as its inverse LSI operator using one, two, or n two-dimensional sheared interferograms. The spatial frequency response of the shearing interferometer is well known and for the reader's convenience, it is briefly revisited in a new perspective. It is however less well-known and more interesting to analyze the spatial distribution of the sheared data as well as the spatial topology of the recovered phase produced by some inverse LSI operators. Also we define a useful space of functions S with the property that any sheared data available, along any direction, may be used to recovered a smooth continuous phase with the bonus property of fully covering the pupil of the wavefront being tested. These combined aspects allow us to find the best possible wave-front reconstruction from the available sheared data using one, two or n sheared interferograms.