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Color images are commonly captured with sensor arrays covered with a mosaic of rgb-filters. Hence one-chip color imagers (CMOS and CCD color cameras) suffer from color aliasing or color moire effects. In order to overcome these limitations color sensors based on vertically integrated diodes were realized. The complete color information of the color aliasing free sensor can be detected at the same spatial position without using additional optical filters. The color separation is realized by the wavelength dependent absorption of the incorporated material in the depth of the devices. A promising material for sensor application in the visible range is amorphous silicon and its alloys. Thin film systems based on amorphous two terminal and stacked multi terminal devices are fabricated by a low temperature CVD process. The spectral sensitivity of the sensors can be controlled by the optical and optoelectronic properties of the materials on one hand and the design of the devices on the other hand. The operation principle of the sensors will be presented and the different detection concepts will be compared regarding their application in the field of color recognition and digital imaging.

We describe an interferometric technique based on temperature dependent optical path length changes in thin slab of transparent materials, suitable for measuring the thermo-optic coefficients of transparent materials. This technique allows an accurate determination of the fringe shift corresponding to a change in the sample temperature, by means of a two fringe pattern Fourier-transform based processing algorithm for phase retrieval. The principle of measurement of the method and its applications to the measurements of the thermo-optic coefficients of some commercial glasses are presented and discussed.

It is presented an interferometric technique based on fringe projection for measuring the refractive indices of liquids

Investigations are issued on printing documents and security papers in offset using pastel spot colours combined with digital printing using process colours. Prints produced by several printing techniques are compared with forgeries made by todays most popular counterfeit techniques. General moire deduction is given for two different raster ruling. Suggestion to combined printing procedures of security programme are given, as well as recommendations to future investigations.

Comparison between moire and X-ray findings in structural kyphosis

Moiré effects have long been used for various applications in many different fields, including metrology, strain analysis, optical alignment, etc. In the present survey we describe some of the main applications of the moiré effect in the field of document and product security. We review the main families of moiré-based anticounterfeiting methods, compare them, and explain how they can be used for such security applications.

The aim of this work was to clarify by Moiré topography the morphological criteria for arrangement of teeth. The alveolar crest line and alveolar crest zone were defined by Moiré topography photographs from 139 upper edentulous stone casts and 20 upper and lower casts which were mounted to articulators. From the results the overlap area between upper and lower alveolar crest zones was classified into 6 types. It is suggested that the overlap areas and the angle between interalveolar lines are very useful as criteria for posterior tooth arrangement in clinical procedures.

Three dimensional analysis of the face using Moire Topography has been carried out over a period of 3 years. The applicability of this method has already been reported in 1982. In the treatment of two cases of skeletal class III malocclusion, one case was dealt by Le Fort I type Osteotomy, and the other by maxillary protractive appliance. Satisfactory results were obtained. And the effectiveness the three dimensional analysis using Moire Topography was shown in pre and post treatment diagnosis.

Interference effects in finite sections of one-dimensional moiré crystals are investigated using a Landauer-Büttiker formalism within the tight-binding approximation. We explain interlayer transport in double-wall carbon nanotubes and design a predictive model. Wave function interference is visible at the mesoscale: in the strong coupling regime, as a periodic modulation of quantum conductance and emergent localized states; in the localized-insulating regime, as a suppression of interlayer transport, and oscillations of the density of states. These results could be exploited to design quantum electronic devices., This work was supported by Spanish MINECO (the Severo Ochoa Centers of Excellence Program under Grant No. SEV- 2017-0706), Spanish MICIU, AEI and EU FEDER (Grants No. PGC2018-096955-B-C43), Generalitat de Catalunya (Grant No. 2017SGR1506 and the CERCA Programme), and the European Union MaX Center of Excellence (EU-H2020 Grant No. 824143). ZZ acknowledges financial support by the Ramon y Cajal program RYC-2016-19344 (MINECO/AEI/FSE, UE) and the Netherlands Sector Plan program 2019–2023. MJV acknowledges funding by the Belgian FNRS (PDR G.A. T.1077.15–1/7 and a sabbatical “OUT” grant at ICN2), and computational resources from the Consortium des Equipements de Calcul Intensif (CECI, FRS-FNRS G.A. 2.5020.11) and Zenobe/CENAERO funded by the Walloon Region under G.A. 1117545. NW has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No. 754558. We acknowledge computer resources at MareNostrum4 at Barcelona Supercomputing Center (BSC), provided through the PRACE Project Access (OptoSpin project 2020225411) and RES (activity FI-2020-1-0014), and technical support provided by the Barcelona Supercomputing Center.

We examined by low-energy electron diffraction and scanning tunneling microscopy the surface of thin Cu films on Pt(111). The Cu/Pt lattice mismatch induces a moire modulation for films from 3 to about 10 ML thickness. We used angle-resolved photoemission spectroscopy to examine the effects of this structural modulation on the electronic states of the system. A series of hexagonal- and trigonal-like constant energy contours is found in the proximity of the Cu(111) zone boundaries. These electronic patterns are generated by Cu sp-quantum well state replicas, originating from multiple points of the reciprocal lattice associated with the moire superstructure. Layer-dependent strain relaxation and hybridization with the substrate bands concur to determine the dispersion and energy position of the Cu Shockley surface state.

In this thesis, ultra-thin dielectric layers on metal substrates are studied mainly by scanning tunneling microscopy and scanning tunneling spectroscopy. In chapter 2, field emission resonances, i.e. bound states in the potential well between sample and tip with an applied voltage, are used to determine the local work function on a sample with patches of different structural composition. To do so, a simple theoretical model is developed and used to simulate the peak positions of the measured dI/dV spectra. In the present case the sample is a Ag(100) surface covered by up to three monolayers of NaCl. The presented method is also applicable to other systems suitable for STM measurements. Additionally, the surface potential is locally probed in the dipole layer region between domains of different work function. In chapter 3, new molecular structures on silver surfaces are presented, that are formed by a mixture of gases. This mixture contains the small molecules H2, H2O, CO, CO2, and N2. No final conclusion can be drawn on the chemical nature of these structures due to the impossibility of the scanning tunneling microscope to determine chemical species. But already the presence of these structures indicates that there is a multitude of unknown interactions, that are possible between a transition metal surface and even smallest molecules. In chapter 4, the moiré pattern is described that a BC3 film creates on a NbB2(0001) surface. As the growth of the BC3 sheet is incommensurate, a moiré pattern is formed that modulates the apparent height of the atoms on the STM images, i.e. the local density of states. The BC3 layer exhibits a completely different behavior than the closely related graphite layer, because it is transparent for the tunnel current. In the present case, the BC3 layer is visible on the STM images only by its moiré effect.

In a previous recent paper we discussed the limitations of the Fourier-based model in the prediction of visible moire effects. Here, we extend the discussion to other mathematical models that are also being used in the moire theory: the classical indicial equations method for modelling the moire fringes between periodic or curvilinear gratings, and two methods that are used to model different facets of the moire effects between correlated aperiodic layers. We discuss the limitations of each model, explain their significance, and suggest possible ways to overcome them.

Secure documents often comprise an information layer that is hard to reproduce. Moiré techniques for the prevention of counterfeiting rely on the superposition of an array of transparent lines or microlenses on top of a base layer containing hidden information. Level-line moirés consist of shapes that appear to be beating upon relative translation of a revealing grating on top of a base, in which the desired information is encoded. Usually, the base only contains the information corresponding to one moiré. In order to increase the difficulty of counterfeiting, we use tessellations to incorporate two or more moirés within the same layer. With the method we propose, the information corresponding to up to seven level-line moirés can be embedded within a single base layer. The moirés are recovered with a revealer printed on a transparency or with an array of cylindrical lenses. This method is general and can be extended to other fabrication technologies.

Modern moiré theory is largely based on the Fourier approach. And yet, it seems that the Fourier theory by itself cannot answer all questions related to moiré effects. We present some visible phenomena in the superposition of periodic structures (such as line gratings) that are not captured by the Fourier approach. We discuss their significance, and provide possible explanations. In particular, we introduce the infinite module spanned by the frequencies of the original individual layers as a main tool in the moiré theory. We discuss its significance on the visible periodicities in the layer superposition-either real moiré effects, or pseudo-moiré (modulation) effects having no corresponding impulses in the Fourier spectral domain.

Moiré effects appear when two sets of periodic structures are superimposed. By combining advanced micro-fabrication technologies and the moiré theory, we are able to obtain visually appealing moirés. Specific metallic patterns are created on one side of a substrate by lithography and etching of an aluminium film. On the other side of the substrate, an array of micro-lenses is fabricated in order to sample these metallic patterns. These new moirés can be recognized by the bare eye. They display text or symbols that move when observed under different viewing angles.

This thesis presents a study of the magnetism of surface supported atoms performed principally with XMCD spectroscopy and multiplet calculations. The objective of the research was twofold: first, to study the underlying interactions and conditions governing the magnetization stability of surface supported atoms, with the aim of achieving long magnetic lifetimes, and second, to assemble single atom magnets in an ordered pattern. Through our study of $4f$ lanthanide atoms on supporting substrates, we established that their magnetic stability is governed by their quantum level structure, in particular their ground $J_z$ state and the height of the energy barrier for thermally assisted magnetization reversal. These features are ruled through the crystal field interaction with their supporting surface. The adsorption site of adatoms governs the symmetry of the crystal field and, consequently, the coupling between the different $J_z$ levels. This in turn enables magnetization reversal either through quantum tunneling between $J_z$ states or via scattering with the electrons and phonons of the substrate. To reduce the scattering events, it is necessary to decouple the adatoms from the metal substrate by using decoupling layers. Here we show that a single layer of graphene is sufficient to decouple Dy atoms from the underlying Ir(111) substrate, resulting in a magnetic lifetime of about 1000~s at 2.5~K. In addition, we show that the moiré pattern of the graphene/Ir(111) surface can be used as a template for the self-assembly of these single atom magnets into well ordered superlattices. Further, by studying multiple graphene/metal substrates we show that the interaction of graphene with the supporting substrate greatly influences the magnetization stability of adsorbed atoms. Finally, we show that replacing graphene with an insulating layer does not result in a stable magnetization of adsorbed atoms if its superior decoupling is not accompanied with an adequate crystal field symmetry.

Micro-optical elements are optical elements having size or details in the range of the micrometer scale. The emergency of such elements is strongly linked to the development made in the fabrication techniques during the nineties to follow the still actual trend of miniaturization. From this time it has been convenient to separate micro-optical element having refractive or reflective optical design from those ones having strictly diffractive design. In the present thesis we are in between this two fields and from conventional refractive optical elements, different features of physical optics like diffraction, polarization or interference effects are added. We start by adding the birefringent property of liquid crystal polymers (LCP) to microlenses. The interest to employ LCP is linked to the fact that bulky birefringent structures of various shapes can easily be obtained by embossing. Moreover the choice of the optical axis of this material can be chosen by boundary conditions imposed by the different surfaces embedding the liquid crystal. Using this material a micro-optical device allowing the increase of the efficiency of conventional polarizer has been designed, simulated and realized. We continue by studying the influence of the aperture size on the position of the peak irradiance of microlenses. This diffractive effect of the aperture limitation is known as the focal shift which tends to decrease the real focal length obtained from paraxial geometric optics. In the frame of this thesis, we pursue the investigation and show that this effect could be advantageously used to obtain achromatic microlenses. In the frame of beam shaping applications we realized diffusers with very narrow angular distribution. These diffusers allow high energy throughputs and homogeneity distribution for highly coherent sources employed in conventional Fly's eye condensers. The consequences of coherent sources used in such beam shaper are discused in detail and rules are given to employ our diffusers in such systems. To finish, we developed and characterized a new method to fabricate concave microlenses with diffraction limited property and applied them in the realization of optical diffusers.