A fast-Fourier-transform method of topography and interferometry is proposed. By computer processing of a noncontour type of fringe pattern, automatic discrimination is achieved between elevation and depression of the object or wave-front form, which has not been possible by the fringe-contour-generation techniques. The method has advantages over moire topography and conventional fringe-contour interferometry in both accuracy and sensitivity. Unlike fringe-scanning techniques, the method is easy to apply because it uses no moving components.

Fourier-transform method of fringe-pattern analysis for computer-based topography and interferometry

Fringe projection techniques: Whither we are?

To improve the performance of particle image velocimetry in measuring instantaneous velocity fields, direct cross-correlation of image fields can be used in place of auto-correlation methods of interrogation of double- or multiple-exposure recordings. With improved speed of photographic recording and increased resolution of video array detectors, cross-correlation methods of interrogation of successive single-exposure frames can be used to measure the separation of pairs of particle images between successive frames. By knowing the extent of image shifting used in a multiple-exposure and by a priori knowledge of the mean flow-field, the cross-correlation of different sized interrogation spots with known separation can be optimized in terms of spatial resolution, detection rate, accuracy and reliability.

Theory of cross-correlation analysis of PIV images : Image analysis as measuring technique in flows

In recent years, both industrial and academic world are focussing their attention toward the development of sustainable composites, reinforced with natural fibres. In particular, among the natural fibres (i.e. animal, vegetable or mineral) that can be used as reinforcement, the basalt ones represent the most interesting for their properties. The aim of this review is to illustrate the results of research on this topical subject. In the introduction, mechanical, thermal and chemical properties of basalt fibre have been reviewed. Moreover, its main manufacturing technologies have been described. Then, the effect of using this mineral fibre as reinforcement of different matrices as polymer (both thermoplastic and thermoset), metal and concrete has been presented. Furthermore, an overview on the application of this fibre in biodegradable matrix composites and in hybrid composites has been provided. Finally, the studies on the industrial applications of basalt fibre reinforced composites have been reviewed.

A review on basalt fibre and its composites

http://eia.udg.es/~qsalvi/papers/2010-PR.pdf

A state of the art in structured light patterns for surface profilometry

Overview of diffusion measurements by optical techniques

In this study the Talbot effect with a Ronchi grating is applied to measurement of shift. It is shown that by using a measurement procedure based on the Fourier transform a cosine grating can be replaced by a Ronchi grating. Two different methods for data reduction and some experimental results are given.

https://iopscience.iop.org/article/10.1088/1464-4258/4/6/383/pdf

Displacement measurement using the Talbot effect with a Ronchi grating

The possibility of employing a digital speckle pattern interferometer with optical fibers for nondestructive testing of artwork has been evaluated. A simple and accurate fiber-optic interferometer, able to perform real-time measurements in a hostile environment, has been realized with a minimum of optical components and a minimum of adjustments. As a result a deformation map of wooden panel paintings or mural frescoes under thermal stress may be depicted. Experimental results, obtained by the application of this interferometer both to laboratory models and to mural frescoes in situ, are presented.

Domenica Paoletti

Papers

Overview of diffusion measurements by optical techniques

Displacement measurement using the Talbot effect with a Ronchi grating

Artwork diagnostics with fiber-optic digital speckle pattern interferometry

A qualitative method for combining thermal imprints to emerging weak points of ancient wall structures by passive infrared thermography – A case study

Contouring of artwork surface by fringe projection and FFT analysis