Coherence-polarization properties of fields radiated from transversely periodic electromagnetic sources

Planar electromagnetic sources characterized by a periodic variation of their beam coherence-polarization matrix are investigated, as far as the polarization features of the radiated fields are concerned, within the framework of the paraxial approximation. A propagation scheme based on plane-wave decomposition leads to a longitudinal periodicity of the polarization properties of the field, thus extending the Talbot effect to the case of partially coherent electromagnetic sources. The polarization features of beams radiated from sources of this type are illustrated by means of simple examples. In particular, it is shown that completely unpolarized sources with uniform intensity profiles can be easily realized, for which the propagated field becomes perfectly polarized across some transverse planes, and vice versa

Potentiality of 3D laser profilometry to determine the sequence of homogenous crossing lines on questioned documents

The determination of the sequence of line crossings is still a current problem in the field of forensic documents examination. Optical examination, lifting technique, ESDA technique, and electron microscopy are the most widely used methods for the determination of the writing order of crossing texts. However, at present many examinations of intersecting lines result in an inconclusive opinion, particularly if the same type and colour of ink is involved. This paper presents the potentiality of the 3D laser profilometry, which has been to determine the chronological sequence of homogenous ‘‘crossing lines’’. The laser profilometry, illustrated in this paper, has been developed on a conoscopic holography based system. It is a non-contact three-dimensional measuring system that allows producing holograms, even with incoherent light, with fringe periods that can be measured precisely to determine the exact distance to the point measured. This technique is suitable to obtain a 3D micro-topography with high resolution also on surfaces with unevenness reflectivity (usual for the paper surface). The proposed technique is able to obtained 3D profile in non-invading way. Therefore, the original draft are not physically or chemically modified, allowing a multi-analysis in different times. The experiments performed with line crossings database show that the proposed method is able of ‘‘positive identification’’ of writing sequence in the majority of the tests. In absence of a positive identification, the result has been "inconclusive" (no false determination did occur in this work)

La pressione dei tratti di scrittura: pressione vs chiaroscuri

Ogni individuo eroga nella scrittura una serie di forze che lo contraddistinguono. Tali forze, con l’ausilio degli strumenti scrittori, si esplicano come pressione scrittoria sul foglio. In particolare, la pressione scrittoria dipende: dalle forze esercitate durante la scrittura; dalle caratteristiche della penna utilizzata; dal foglio; dal piano di appoggio del foglio; dalla posizione di scrittura. In generale l’analisi dei chiaroscuri presenti in una scrittura vengono associati alla pressione scrittoria. Purtroppo le variazioni di inchiostrazione possono dipendere da anomalie nella modulazione del gesto e non necessariamente collegate alla pressione. Le analisi strumentali su una manoscritta (o l’osservazione visiva tramite luce radente) possono tentare di rilevare le modalità di distribuzione della pressione osservando i solchi lasciati dalla punta della penna. Per associare queste modulazioni alle caratteristiche individuali dello scrivente è indispensabile avere “conoscenza” di come lo scritto è stato generato. In particolare è indispensabile avere “conoscenza” degli strumenti scrittori utilizzati

Artworks Diagnostics with Fiber Optics DSPI

Abstract not availableNA-NOT AVAILABL

Fourier transform for sandwich holograms evaluation

A system based on 2D Fourier transform method for accurate determination of the interference phase distribution from a sandwich interferogram with carrier fringes is presented. The technique is particularly suitable for an evaluation of surface deformation in static as well as dynamic processes. Some practical applications are shown

Diffractive optical element-based profilometer for surface inspection

We introduce a new 3-D sensor based on a diffractive optical element (DOE). Structured light is obtained by the interference of two beams. The design of the projection unit has the following features: the system is very simple, small and cheap and the fringe spacing is easily adjustable. Fringes generated by the DOE interferometer are analyzed by Fast Fourier Transform (FFT) method, which produced a 3-D perspective plot. The technique and the experimental results of real surface profiles are given

A System for the sampling of inhalable airborne particles

This paper describes an instrument developed for the semi-continuous measurement of aerosol mass and its classification into three classes. These classes have been chosen to evaluate the health hazards caused by inhalable particles. The instrument takes samples through three probes, each providing different cut-off points approximately 15 microm, approximately 4 microm, approximately 2 microm) and collects airborne particles on circular membrane filters. The increase in weight is measured by the beta-ray attenuation method