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Objectiu: Analitzar el comportament espectral d'una lent intraocular (LIO) trifocal de perfil difractiu sinusoïdal (Acriva Trinova, VSY Biotechnology, The Netherlands). Mètode: L'anàlisi es realitza de forma objectiva en banc òptic, inserint la LIO Acriva Trinova en un ull model. S'utilitza un test objecte il·luminat consecutivament per 3 LEDs de longitud d'ona (λ) igual a 455, 530 i 625 nm i s'utilitzen dues mides de pupil·la, de 3,0 i 4,5 mm al pla de la LIO. A través de la funció de transferència de modulació (MTF) s'analitza la qualitat de les imatges a tot el recorregut al llarg de l'eix òptic, des de la visió de prop fins a la visió de lluny (through-focus) per obtenir, per a cada λ, la localització dels tres focus de la lent i la qualitat òptica a cadascun. S'obté així l'aberració cromàtica longitudinal (ACL) a cada focus i la dependència de la qualitat òptica a cada focus versus λ. Resultats: A les corbes MTF through-focus s'observa manca de concordança entre els resultats proporcionats per la λ per a la qual s'ha dissenyat la lent (λ0≈530 nm) i la resta de longituds d'ona analitzades. Conclusions: La potència i la qualitat òptica de la LIO Acriva Trinova depèn de la longitud d'ona. Aquesta lent té un comportament diferent al d'altres LIOs trifocals segurament per tenir diferent assignació de focus amb els ordres de difracció. Objetivo: Analizar el comportamiento espectral de una lente intraocular (LIO) trifocal de perfil difractivo sinusoidal (Acriva Trinova, VSY Biotechnology, The Netherlands). Método: El análisis se realiza de forma objetiva en banco óptico, insertando la LIO Acriva Trinova en un ojo modelo. Se utiliza un test objeto iluminado consecutivamente por 3 LEDs de longitud de onda (λ) igual a 455, 530 y 625 nm y se utilizan dos tamaños de pupila, de 3,0 y 4,5 mm en el plano de la LIO. A través de la función de transferencia de modulación (MTF) se analiza la calidad de las imágenes en todo el recorrido a lo largo del eje óptico, desde la visión de cerca hasta la visión de lejos (through-focus) para obtener, para cada λ, la localización de los tres focos de la lente y la calidad óptica en cada uno de ellos. Se obtiene así la aberración cromática longitudinal (ACL) en cada foco y la dependencia de la calidad óptica en cada foco versus λ. Resultados: En las curvas MTF through-focus se observa falta de concordancia entre los resultados proporcionados por la λ para la que se ha diseñado la lente (λ0≈530 nm) y el resto de las longitudes de onda analizadas. Conclusiones: La potencia y la calidad óptica de la LIO Acriva Trinova depende de la longitud de onda. Esta lente tiene un comportamiento diferente al de otras LIOs trifocales seguramente por tener diferente asignación de focos con los órdenes de difracción. Objective: To analyze the spectral behavior of a trifocal intraocular lens (IOL) with sinusoidal diffractive profile (Acriva Trinova, VSY Biotechnology, The Netherlands). Method: The analysis is performed objectively on an optical bench, inserting the Acriva Trinova IOL into a model eye. A test object consecutively illuminated by 3 LEDs of wavelength (λ) equal to 455, 530 and 625 nm is used, and two pupil sizes in the plane of the IOL, 3.0 and 4.5 mm, are used. Through the modulation transfer function (MTF), the quality of the images is analyzed throughout the path along the optical axis, from near vision to far vision (through-focus) to obtain, for each λ, the location of the three foci of the lens and the optical quality in each of them. Thus, the longitudinal chromatic aberration (LCA) in each focus and the dependence of the optical quality in each focus versus λ are obtained. Results: In the MTF through-focus curves, a lack of agreement is observed between the results provided by the λ for which the lens has been designed (λ0≈530 nm) and the rest of the analyzed wavelengths. Conclusions: The power and optical quality of the Acriva Trinova IOL depends on the wavelength. This lens behaves differently from other trifocal IOLs, probably because it has a different focus assignment with the diffraction orders.

In this work, we introduce a spatial filtering mechanism that can be effectively utilized by photonic crystals. The phenomenon utterly expressed here is Rayleigh-Wood’s anomaly. Such a mechanism is realized and optimized via RCWA (Rigorous Coupled Wave Analysis) together with a global optimization algorithm for both s and p polarized inputs. The calculated transmission and reflection spectra of such mechanisms show that the Rayleigh anomaly provides the necessary sharp transmission profile near the critical wavelength from which the diffraction can occur.

Earth Observation satellite missions can provide global and frequent coverage. In the past decade we have seen an explosion of these missions based on three unit CubeSats, notably with Planet and Spire constellations of visible and near-infrared imagers and GNSS-Radio Occultations payloads. One of the most important parts of these type of payloads is the antenna, which is limited due to the dimensions of the CubeSats. Today, the largest deployable antenna for CubeSats has a diameter of 50 cm and it was part of RainCube rain radar. ESA is currently sponsoring two studies to develop a 1 m deployable reflector antenna for CubeSats. Although the most common solutions are the deployable reflectors, Fresnel Zone Plate antennas are a simple type of antennas that can overcome some of the technical limitations of these reflectors. In this paper we will present the design and tests of a deployable Fresnel Zone Plate antenna with 155 cm diameter, at a distance of 58 cm from the feeder. During the design, the modularity of the system has been considered, so that other antenna types can also be deployed. This antenna has a triangular shape, and each end is attached to a telescopic carbon fiber rod, which is deployed by means of a toothed belt that pushes them from its inner part. Each toothed belt is pushed with a DC motor. If accepted for a launch of opportunity, this antenna will be used in a GNSS-Radio Occultations payload onboard 3Cat-8, one of the future satellite missions of the UPC NanoSat Lab

The deformation behavior of Ti–6Al–4V processed by laser powder bed fusion (LPBF) is investigated by in situ high-energy synchrotron X-ray diffraction (HEXRD) during uniaxial compression. The initial microstructure of the alloy consists of a fine lamellar a¿+¿ß microstructure where a lamellae are separated by thin continuous ß layers within prior ß grains. The anisotropy of the alloy is studied in the deformation direction using samples that are built at the angles of 0°, 45°, and 90° with respect to the LPBF base plate. The sample oriented at 0° presents higher strength–ductility trade-off compared with the conditions oriented at 45° and 90°. The in situ HEXRD experiments continuously reveal the microstructure response during deformation and that the textures for each orientation are associated with a different activation sequence of deformation mechanisms.

[ES] La búsqueda de nuevos compuestos químicos con propiedades específicas representa uno de los retos más significativos, no sólo para la industria químico-farmacéutica, sino para el mundo científico en general. Los boratos son compuestos con muy buenas prestaciones mecánicas y ópticas que, dopados con tierras raras adquieren propiedades luminiscentes únicas. Para la aplicación de estas propiedades extraordinarias en un sensor de altas prestaciones es necesario garantizar la estabilidad estructural del compuesto y analizar su comportamiento bajo las condiciones de operación. En este trabajo se analiza la estabilidad estructural del borato de tántalo (TaBO4) en un intervalo de presiones desde presión atmosférica hasta 69.3 gigapascales. Para ello, se realizan experimentos de difracción de rayos X de compresión dinámica en los sincrotrones ALBA y DIAMOND light source. Los datos obtenidos son analizados mediante un refinamiento Rietveld. Los resultados validan el potencial de este material como un posible candidato para la construcción de sensores de alta presión., [EN] Research in new advanced materials is a crucial enterprise, not only for the chemical and pharmaceutical industries, but for scientific community. Borates are chemical compounds with very interesting mechanical and optical properties. When doped with lanthanoids or actinoids, borates acquire unique luminescent properties. To leverage such properties in a highperformance pressure sensor, it is necessary to analyze the properties of the material under relevant load conditions and to ensure its stability. In this work, we study the structural evolution of tantalum borate (TaBO4) across a wide pressure range, from atmospheric pressure up to 69.3 gigapascal. To this end, X-ray diffraction experiments under dynamic compression were conducted at the ALBA and DIAMOND light source synchrotron. The data generated were analyzed using a Rietveld refinement strategy. Our results validate the potential of tantalum borate for use as a high-pressure sensor, [CA] La cerca de nous compostos químics amb propietats cada vegada més específiques representa un dels reptes més significatius no sols per a la industria químico-farmecèutica, sinó per al món científic en general. Els borats són compostos amb molt bones prestacions mecàniques i òptiques que, dopats amb terres rares adquireixen propietats luminescents úniques. Per a l’aplicació d’aquestes propietats extraordinàries en un sensor d’elevades prestacions és necessari assegurar la estabilitat estructural del compost i analitzar el comportament d’aquest baix les condicions d’operació. En aquest treball s’analitza la estabilitat estructural del borat de tàntal (TaBO4) en un interval de pressions des de la pressió atmosfèrica fins a 69.3 gigapascals. Amb tal fi, es realitzen experiments de difracció de raigs X de compressió dinàmica en los sincrotrones ALBA y DIAMOND light source. Les dades obtingudes són analitzades amb un refinament Rietveld. Els resultats validen el potencial d’aquest material com a un plausible candidat per a la construcció de sensors d’altes pressions.

Purpose: Compare subjective (Rx) and objective (ObjRx) refractions outcomes with two autorefractors models and an aberrometer in eyes implanted with a hydrophobic trifocal IOL (FineVision POD F GF, Physiol, Liége, Belgium) and a hydrophilic one (FineVision POD F, Physiol, Liége, Belgium). Methods: Prospective comparative cohort study, with 100 subjects randomly assigned to either the POD F group (n = 50) or the POD F-GF group (n = 50). Postoperative eye examinations at 1-month visit included seven result sets, one for each assessment method: Rx, AR (automated refraction measured with the autorefractor KR8800), WF-P (Zernike-coefficients-based objective refraction, photopic pupil size), WF-M (Zernike-coefficients-based objective refraction, mesopic pupil size), WF-4 (Zernike-coefficients-based objective refraction, 4 mm pupil), OPD-C (automated refraction measured with the aberrometer OPD in the central pupil/photopic conditions), and OPD-M (automated refraction measured with the aberrometer OPD under mesopic conditions). Results: Mean differences between ObjRx and Rx reached statistical significance for sphere and spherical equivalent (M) only with OPD-C in the POD F-GF group. All ObjRx methods showed significant differences with Rx in the POD F group, with some values differing by more than 0.50 D (-0.58 D in M for the WF-P). Bland Altman plots showed better agreement for the astigmatic components, and for sphere and spherical equivalents in both IOL groups measured with AR and OPD-M. Conclusions: None of the objective methods of refraction evaluated in this study were as reliable as the subjective refraction, irrespective of the lens material, but POD F-GF ObjRx seems to differ less with Rx than POD F ObjRx values. Award-winning

Vacuum fluctuations are known to produce electron diffraction leading to decoherence and self-interference. These effects have so far been studied as either an extension of the Aharonov–Bohm effect in front of a planar perfect conductor or through path integral analysis. Here, we present a simpler, general, and rigorous derivation based on a direct solution of the quantum electrodynamic aloof interaction between the electron and a material structure in the temporal gauge. Our approach allows us to study dissipative media, for which we show examples of electron wave function shaping due to the interaction with real-metal surfaces. We further present a proof of the relation between the phase associated with vacuum fluctuations and the Aharonov–Bohm effect produced by the image self-interaction that is valid for arbitrary geometries. Besides their fundamental interest, our results could be useful for on-demand patterning of electron beams with potential application in nondestructive nanoscale imaging and spectroscopy.

A dual model with a nonlinear proton Regge trajectory in the missing mass (M2X) channel is constructed. A background based on a direct-channel exotic trajectory, developed and applied earlier for the inclusive electron-proton cross section description in the nucleon resonance region, is used. The parameters of the model are determined from the extrapolations to earlier experiments. Predictions for the low-mass (2 < M2X < 8 GeV2) diffraction dissociation cross sections at the LHC energies are given.

Among the severe plastic deformation techniques, the equal channel angular pressing (ECAP) has drastically improved the mechanical properties of the processed alloys. However, information regarding friction phenomenon, which modifies the deformation at the surface and the heterogeneity microstrain state produced by the process itself, is still scarce. In the present work, the deformation heterogeneity and the friction effect, at the surface in the bulk material of the 6061-T6 aluminum alloy processed by ECAP, is presented and discussed. The residual stress (RS) measurements were performed by means of X-Ray diffraction. By means of synchrotron diffraction, volumetric sections of the ECAPed samples were characterized. Finite element analysis showed a good agreement with the experimentally obtained residual stress and microhardness mapping results. The study also showed that the highest deformation zones were located at the outer parts of the deformed samples (top and bottom), while the inner zone showed strain oscillations of up to 49±2 MPa.

Propòsit: Determinar la informació de difusió intraocular del paràmetre FSI en pacients sans i pacients amb alteracions cornials. Disseny: Es tracta d'un estudi experimental, observacional, transversal i prospectiu de casos no consecutius. Mètode: 33 ulls de pacients sans i 28 ulls amb patologies cornials s'han inclòs en aquest estudi (6 amb còrnia guttata, 8 amb distròfia de Fuchs i 14 amb distròfia de la membrana basal). Tots els pacients van ser avaluats, diagnosticats i classificats per oftalmòlegs de l'Institut de Microcirugía Ocular (IMO). Les variables analitzades estadísticament van ser les següents: Agudesa Visual (AV) logMAR, mesures de qualitat òptica ocular, Sthrel ràtio, MTFcut-*off, OSI i FSI amb l'instrument HD Analyzer i RMS d'alt ordre amb el aberrómetro WASCA Analyzer. El paràmetre FSI es va obtenir mitjançant el processament d'imatges de doble pas (DP) en diferents excentricitats. Resultats: S'han trobat correlacions estadísticament significatives entre les HOA respecte a OSI (r=0.444

[eng] In physics, it is common to find different phenomena being described by similar equations. A good analogy can make us look at a problem from a different point of view. In that way, ideas may be transferred from one field of science to another, allowing to model new phenomena after previous, well-studied ones. In the case of the field of analogue gravity, systems that mimic certain aspects of the physics of curved spacetimes are studied. In this thesis, we are interested in the analogy between geometry and media. It has been known for several decades that light propagation in a gravitational field is formally equivalent to that in a bianisotropic medium. On the one hand, ray paths are bent due to spacetime curvature. On the other hand, spatial variations of the permittivity and permeability of a material can make light follow curved trajectories. These two phenomena can be related mathematically in the context of transformation optics, which provides the tools to determine the medium parameters necessary to mimic a certain coordinate transformation. Materials with these specific properties are not naturally occurring, therefore, the emergence of metamaterial science at the beginning of the century was needed to realize them. Metamaterials are artificial composite materials with sub-wavelength constitutive elements that exhibit exotic properties. They have been one of the hot topics of the past years given the variety of opportunities they offer: negative refraction, superlenses, indefinite dispersion, invisibility, among many others. In this thesis we study the analogues of two static spacetimes from the point of view of transformation optics: one with spherical symmetry and one with conical geometry. Both cases are inspired by solutions to Einstein’s equations: the Schwarzschild black hole and the cosmic string, respectively. For each case, we derive the permittivity and permeability of the analogous material using Plebanski’s formulation of the electromagnetic constitutive equations. We solve numerically the wave equation in the metamaterial and compare the results with analytical theories. We find that the spherically symmetric spacetime can be mimicked by either an anisotropic or isotropic medium due to its rotational symmetries. This is achieved by performing a coordinate transformation of the general metric to a conformally flat form. We obtain the medium parameters for both cases and apply the results to the case of the Schwarzschild black hole. We simulate the propagation of a Gaussian beam in the two materials and compare the numerical results with the null-geodesics in the Schwarzschild spacetime, finding a good agreement. The cosmic string is an example of a topological defect with conical geometry. A conical space can be interpreted as flat space with a wedge removed. We make use of this transformation to study the wave equation in the cosmic string background. We apply asymptotic diffraction theories to obtain analytical models that describe wave propagation of electromagnetic or gravitational waves (in a certain gauge). We find that our expressions reproduce accurately the results of the numerical simulations in the analogous metamaterial. Moreover, with our models, we can understand the observed diffraction pattern as the interference of four characteristic waves. With this interpretation we can introduce the Fresnel observation zones, which are related to the diffraction maxima. They help localize the regions – in either space or frequency – where the wave effects are more significant. In fact, in the diffraction by a non-compact object such as the cosmic string, we find that the contribution to the field of wave effects such as interference or diffraction can be of the same order as the geometrical optics terms. Furthermore, the conical topology also appears in condensed matter systems as disclinations or wedge dislocations, therefore we expect our results to be applicable in those systems as well., [spa] La investigación en gravitación análoga consiste en el estudio de sistemas físicos donde se pueden reproducir algunos de los fenómenos propios de relatividad general. Esta tesis se centra en la conocida propagación análoga de las ondas electromagnéticas en un espacio-tiempo curvado y en un medio con una permitividad y permeabilidad generalmente anisótropas. Para la realización de este tipo de medios, fue necesaria la aparición de los metamateriales, materiales artificiales diseñados para tener propiedades electromagnéticas fuera de lo común. En este contexto, se estudian modelos análogos a dos objetos estáticos con distinta simetría: uno con simetría esférica y otro con topología cónica. Ambos casos están motivados por soluciones a las ecuaciones de Einstein: el agujero negro de Schwarzschild y la cuerda cósmica, respectivamente. A través de las ecuaciones de óptica de transformación, determinamos los parámetros de los medios análogos a estos espacio-tiempos. Estudiamos la propagación de ondas electromagnéticas en los materiales obtenidos mediante simulaciones numéricas y comparamos los resultados con teorías analíticas, encontrando muy buen acuerdo. Por un lado, los contrastamos con las geodésicas en los espacio-tiempos considerados a través del formalismo Hamiltoniano. Por otro lado, desarrollamos modelos analíticos para describir la difracción de una onda (en principio tanto electromagnética como gravitatoria) debido a la cuerda cósmica. Para ello, usamos teorías asintóticas de difracción en un espacio virtual plano con un déficit de ángulo, ya que es una representación equivalente a la geometría cónica de la cuerda. De este modo, se obtienen expresiones que nos permiten explicar detalladamente los fenómenos ondulatorios de interferencia y difracción que se producen en este espacio-tiempo. Observamos que estos efectos pueden ser comparables a los términos de óptica geométrica: añaden una modulación en la amplificación del campo relacionada con la formación de imágenes dobles propia de la topología de la cuerda. Cabe destacar que estos fenómenos son conceptualmente distintos a los que se podrían esperar en la difracción sobre un objeto sólido como una barra. Utilizando nuestros modelos analíticos, obtenemos el patrón de difracción característico de la cuerda cósmica, que podría ser de interés para su detección.

Materials science and engineering / A 717, 134 - 143 (2018). doi:10.1016/j.msea.2018.01.077, The sequence of activation of deformation mechanisms in a near-β Ti-5Al-5Mo-5V-3Cr alloy quenched from the β-field is investigated as a function of strain during uniaxial compression at 0.001 s$^{−1}$ up to $ε$ = 0.041. Bulk in situ high energy synchrotron X-ray diffraction is applied to follow continuously the evolution of the microstructure of the alloy during deformation and is complemented with metallographic analysis. Stress induced β → α″ transformation takes place together with grain rotation of $β$ upon reaching the yield stress of the alloy at ε = 0.021. During further loading, formation of β sub-grain cells is activated at 4ε ≥4 0.03. The stress-induced martensite forms with a strong texture of {200} α″ planes perpendicular to the compression direction., Published by Elsevier, Amsterdam

Hohner Automáticos S.L. és una empresa principalment dedicada a la fabricació d’encoders.Aquesta tesi doctoral s’ha centrat en la millora i innovació respecte a un tipus de producte anomenat encoder rotatori incremental òptic. Aquest tipus de sensor mesura la posició, velocitat i acceleració a la qual gira un eix d’un motor. L’objectiu ha estat solucionar tres problemes que apareixen quan l’encoder assoleix altes resolucions de mesura: obtenir un compta-voltes (senyal de referència Z) precís, augmentar la resolució al generar un senyal de naturalesa òptica necessari per poder utilitzar un procediment d’interpolació electrònica (encoder amb senyals output de tipus sin/cos) i atacar un problema d’industrialització com és l’Air-Gap entre disc i màscara, el qual esdevé críticament petit ( 30μm) per a resolucions altes. Partint d’una base teórica matemàtica (repassant Series i Integrals de Fourier) i física (Òptica de Fourier i Difracció), s’ha arribat a tres solucions de forma analítica (una per cada problema), les quals s’han implementat de forma numèrica i experimental amb molt bons resultats. L’empresa Hohner Automáticos S.L. ha aplicat dues d’aquestes solucions a la seva gama de productes, amb intenció d’implementar la tercera immediatament. A causa de la magnitud innovadora de dues d’aquestes idees dins el mercat, s’ha demanat una sol·licitud de patent per protegir la Propietat Intel·lectual de les invencions. Hohner Automáticos S.L. is a company mainly dedicated to the manufacture of encoders. This doctoral thesis has been focused on the improvement and innovation related to a type of product called optical incremental rotary encoder. This type of sensor measures the position, speed and acceleration of the shaft of a motor. The objective has been to solve three problems that appear when the encoder reaches high resolution of measurement: obtain a precise turn counter (signal of reference Z), increase the resolution when generating a signal by optical means which has to be able to use in a procedure called 'Electronic interpolation’ (encoder with output signals of sin/cos type) and target an industrialization problem such as the Air-Gap between disc and mask, which becomes critically small (30μm) for high resolutions. Based on a mathematical theoretical basis (reviewing Fourier Series and Integrals) and physics (Fourier Optics and Diffraction), three solutions have been analyzed (one for each problem), which have been implemented in a numerical way and experimental with very good results. Hohner Automáticos S.L. has applied two of these solutions to their products, with the intention of implementing the third one immediately. Due to the innovative magnitude of two of these ideas in the market, a patent application has been requested to protect the Intellectual Property of inventions.

Propòsit: Avaluar clínicament la correlació entre la difusió intraocular (DIO) i les aberracions oculars (ABO) mitjançant l’anàlisi de les imatges de doble pas (DP) en ulls amb cataractes. Metodologia: L’estudi va comptar amb 80 ulls diagnosticats de cataractes nuclears (34), corticals (6), subcapsulars posteriors (3) o mixtes (37), i 22 ulls sans. A tots els pacients se’ls va realitzar un examen refractiu, mesura de l’agudesa visual, i la gradació de les cataractes mitjançant el Sistema de Classificació d’Opacitats de Lents (LOCS III). El protocol també incloïa la mesura de l’índex OSI amb l’HDAnalyzer, ABO mitjançant el sistema de Hartmann- Shack i l’straylight (log[s]) per mitjà del C-Quant. El paràmetre MTFDF es va obtenir per processament de les imatges DP. Resultats: Es van trobar correlacions estadísticament significatives entre OSI i les ABO. D’altra banda, MTFDF va obtenir valors de correlació baixos amb les ABO. Log(s) va presentar una baixa correlació amb ambdós índexs de difusió (OSI i MTFDF) així com amb les ABO. Conclusions: En condicions de laboratori, el paràmetre MTFDF es mostra com una bona eina per mesurar l’efecte de la DIO. Els resultats d’OSI indiquen que és un bon paràmetre de mesura de la DIO en pacients amb cataractes. OSI sembla tenir més influència de ABO que l’índex MTFDF.

We introduce a new method for producing optical needles with tunable length and almost constant irradiance based on the evaluation of the on-axis power content of the light distribution at the focal area. According to theoretical considerations, we propose an adaptive modulating continuous function that presents a large derivative and a zero value jump at the entrance pupil of the focusing system. This distribution is displayed on liquid crystal devices using holographic techniques. In this way, a polarized input beam is shaped and subsequently focused using a high numerical aperture (NA) objective lens. As a result, needles with variable length and nearly constant irradiance are produced using conventional optics components. This procedure is experimentally demonstrated obtaining a 53λ-long and 0.8λ-wide needle.

Making use of the diffraction phenomenon, it is designed and developed a versatile low-cost optic spectrometer. After its wavelength calibration using diodes-lasers and amplitude calibration using a continuous source, it is possible to characterize the spectrum of different light sources. Results are compared with ones are obtained with a commercial spectrometer., En aquesta memòria es detalla el procés de disseny, desenvolupament i prototipatge d’un sistema de mesura de l’espectre visible. L’objectiu a complir és l’obtenció d’un dispositiu reproduïble, competitiu a nivell tècnic amb els models comercials de docència actuals, amb un preu més econòmic i totalment accessible. El dispositiu resultant reuneix les característiques de ser portàtil, versàtil, compacte, econòmic, accessible i distribuïble. El cor del projecte és el software, que com a característica clau permet ser utilitzat amb pràcticament qualsevol càmera, és fàcilment modificable i permet ser executat després d’una instal·lació bàsica. El prototipatge s’ha realitzat amb una càmera comercial amb connexió USB amb la fi de trobar un balanç entre assequibilitat i resolució del producte final: un preu vint voltes més econòmic i una resolució que s’aproxima a l’espectrofotòmetre comercial emprat com a referència.

We show that modulation instability (MI) can be suppressed in vertical external cavity surface emitting lasers (VECSELs) by introducing a periodic spatio-temporal modulation of the pump profile which in turn allows a simple flat-mirror configuration. The stability analysis of such pump modulated flat-mirror VECSELs is performed by a modified Floquet method and results are confirmed by full numerical integration of the model equations. It is found that the amplitude of the modulation as well as its spatial and temporal frequencies are crucial parameters for high spatial beam quality emission. We identify regions of complete and partial stabilization in parameter space for VECSELs with different external cavity lengths. The proposed method is shown to efficiently stabilize VECSELs with cavity lengths ranging from millimetres up to centimetres. However, the applicability of this method becomes limited for micro-meter-long cavities due to strong intrinsic relaxation oscillations.

Adoptem la noció de difracció proposada per Karen Barad (2007) per reavaluar les relacions entre l'art contemporani convencional (ACC) i l'art dels nous mitjans (ANM), sobre les quals s'ha discutit durant molts anys com a part d'un debat un xic controvertit. La nostra lectura difractiva posa en relleu diferències, grans i petites però conseqüents, entre aquestes pràctiques artístiques. No suavitzarem les tensions que destaquen en anteriors debats sobre ANM i MCA, sinó que utilitzarem el terme de Barad, «embolic», per suggerir que hi ha «embolics» generatius, així com diferències productives, entre aquestes pràctiques. Ampliem el debat considerant quines diferències importen, per a qui (artistes, galeristes, científics) i com aquestes diferències emergeixen a través d'intraaccions materials i discursives. Propugnem un nou terme, «pràctiques artístiques difractives», i suggerim que aquestes pràctiques artístiques van més enllà de la bifurcació d’ANM i MCA per a reconfigurar parcialment les pràctiques entre art, informàtica i humanitats., We engage with Karen Barad’s notion of diffraction (2007) to re-evaluate the relations between mainstream contemporary art (MCA) and new media art (NMA) that have been discussed for many years as part of a somewhat contentious debate. Our diffractive reading highlights both large and small but consequential differences between these art practices. We do not smooth over the tensions highlighted in earlier discussions of NMA and MCA. Instead we use Barad’s term ‘entanglement’ to suggest that there are generative ‘entanglements’, as well as productive differences, between these practices. We extend the debate by considering which differences matter, for whom (artists, gallerists, scientists) and how these differences emerge through material-discursive intra-actions. We argue for a new term, diffractive art practices, and suggest that such art practices move beyond the bifurcation of NMA and MCA to partially reconfigure the practices between art, computation and humanities., Adoptamos la noción de difracción propuesta por Karen Barad (2007) para reevaluar las relaciones entre el arte contemporáneo convencional (ACC) y el arte de los nuevos medios (ANM), sobre las que se ha discutido durante muchos años como parte de un debate algo controvertido. Nuestra lectura difractiva pone de relieve diferencias, grandes y pequeñas pero consecuentes, entre estas prácticas artísticas. No suavizamos las tensiones puestas de relieve en anteriores debates acerca de ANM y MCA, sino que utilizamos el término de Barad, «enredo», para sugerir que existen «enredos» generativos, así como diferencias productivas, entre dichas prácticas. Ampliamos el debate considerando qué diferencias importan, para quién (artistas, galeristas, científicos) y cómo dichas diferencias emergen a través de intra-acciones materiales y discursivas. Propugnamos un nuevo término, «prácticas artísticas difractivas», y sugerimos que dichas prácticas artísticas van más allá de la bifurcación de ANM y MCA para reconfigurar parcialmente las prácticas entre arte, informática y humanidades.

The object is the identification of the micro-crystalline precipitates appearing in historical painting layers produced during the production and also due to the reactivity of the various compounds. For this reason different procedures of preparation of the samples (polishing over glass a substratum or micro-tomming of the samples previously embodied in resin. Each has specific instrumental setups which will be developed in two experiments in the Alba Synchrotron, one in BL04-MSPD beamline (number 2014060905) for painting layer on glass and in the second for the wall paint X-Ray Diffraction is a technique used in materials science to identify the crystalline structures that can appear on the object of interest. In this project, the materials of interest are samples extracted from historical painting and pieces of decorated glass and glazed ceramics. The micrometric size of the paint layers as well as of the colour decoration layers in glass or glazed ceramics requires of a micrometric size beam. Moreover, the complexity of compounds found on those layers (a mixture of original, reaction, weathering and aging compounds) require also of a high brilliance monochromatic beam with tunnable energy. All these requirements force to perform the experiments at a synchrotron light facility. The main goal is to learn about the information that can be obtained from an X-ray diffraction analysis as well as its limitations and in particular the importance of sample preparation. La difracción de rayos X es una técnica utilizada en la ciencia de materiales para identificar las estructuras cristalinas que pueden aparecer en el objeto de estudio. En este proyecto, los materiales de interés son muestras extraídas de pinturas históricas y piezas de vidrio decorado y cerámica vidriada. Debido al tamaño micrométrico de las capas de pintura, así como de las capas de las decoraciones de colores en vidrio o cerámica vidriada, es necesaria el uso de un haz de tamaño micrométrico. Por otra parte, la complejidad de compuestos que se encuentran en las capas (una mezcla de las reacciones resultante de la intemperie y el envejecimiento con los compuestos originales) requieren la utilización de un haz monocromático de alto brillo y energía regulable. Todos estos requisitos obligan a realizar los experimentos en una instalación de luz de sincrotrón. El objetivo principal es aprender sobre la información que se puede obtener a partir de un análisis de difracción de rayos X, así como sus limitaciones y, en particular, la importancia de la preparación de la muestra. La difracció de raigs X és una tècnica utilitzada en la ciència de materials per identificar les estructures cristal·lines que poden aparèixer en l’objecte d’estudi. En aquest projecte, els materials d'interès són mostres extretes de pintures històriques i peces de vidre decorat i ceràmica vidriada. Degut a la mida micromètrica de les capes de pintura, així com de les capes de les decoracions de colors en vidre o ceràmica vidriada, és necessària l’ús d'un feix de mida micromètrica. D'altra banda, la complexitat de compostos que es troben en les capes (una barreja de les reaccions resultant de la intempèrie i l'envelliment amb els compostos originals) requereixen la utilització d'un feix monocromàtic d'alta brillantor i energia regulable. Tots aquests requisits obliguen a realitzar els experiments en una instal·lació de llum de sincrotró. L'objectiu principal és aprendre sobre la informació que es pot obtenir a partir d'una anàlisi de difracció de raigs X, així com les seves limitacions i, en particular, la importància de la preparació de la mostra.

The energy distribution between the distance and near images formed in a model eye by three different apodized diffractive multifocal intraocular lenses (IOLs) is experimentally determined in an optical bench. The model eye has an artificial cornea with positive spherical aberration (SA) similar to human cornea. The level of SA upon the IOL, which is pupil size dependent, is controlled using a Hartmann-Shack wave sensor. The energy of the distance and near images as a function of the pupil size is experimentally obtained from image analysis. All three IOLs have the same base refractive power (20D) but different designs (aspheric, spherical) and add powers (+4.0 D, +3.0 D). The results show that in all the cases, the energy efficiency of the distance image decreases for large pupils, in contrast with the theoretical and simulated results that only consider the diffractive profile of the lens. As for the near image, since the diffractive zone responsible for the formation of this image has the same apodization factor in the spherical and aspheric lenses and the apertures involved are small (and so the level of SA), the results turn out to be similar for all the three IOL designs.

A mathematical model that describes the behavior of low-resolution Fresnel lenses encoded in any low-resolution device (e.g., a spatial light modulator) is developed. The effects of low-resolution codification, such the appearance of new secondary lenses, are studied for a general case. General expressions for the phase of these lenses are developed, showing that each lens behaves as if it were encoded through all pixels of the low-resolution device. Simple expressions for the light distribution in the focal plane and its dependence on the encoded focal length are developed and commented on in detail. For a given codification device an optimum focal length is found for best lens performance. An optimization method for codification of a single lens with a short focal length is proposed.

Current photographic still cameras, in the professional SLR step, are available in two basic sensor sizes, 16x24mm and 24x36mm and both of them can be used with the same or similar range of focal length lenses. Lens aperture determines resolving power and diffraction effects and indeed, MTF function. In order to preserve an acceptable image quality level, it must be taken into account that a high lens resolving power at larger apertures can be replicated by the sensor as a false response or aliasing, while the size of the Airy disc must be related with photo receptors pitch. Provided that a standardized metric of image quality is the system MTF, this work compares different lenses resolving power as a function of aperture with the lens and system MTF; both aliasing and resolution affectations can be observed in the system MTF. Lens resolving power has been measured by visual inspection of the aerial image of an USAF1951 test target through a suitable microscope. The lens PSF and MTF has been measured by means of a Shack-Hartmann optical wave front sensor. The system MTF is measured by the slanted edge method. The different experimental procedures have been applied to two professional SLR cameras equipped with the same general use lens.

Los autores agradecen la colaboración de J. Otón y el apoyo económico del Ministerio de Ciencia e Innovación así como de los fondos FEDER al proyecto DPI2006-05479.

In terms of the Fourier spectrum, a simple but general analytical expression is given for the evanescent field associated to a certain kind of non-paraxial exact solutions of the Maxwell equations. This expression enables one to compare the relative weight of the evanescent wave with regard to the propagating field. In addition, in those cases in which the evanescent term is significant, the magnitude of the field components across the transverse profile (including the evanescent features) can be determined. These results are applied to some illustrative examples.

[spa] Dentro de la denominación --reconocimiento de formas' se engloban todos aquellos métodos mediante los cuales es posible detectar la presencia de una determinada imagen (referencia) dentro de otra (escena). Del conjunto de técnicas ópticas que permiten realizar esta operación, destacan las basadas en la comparación entre los diferentes elementos que forman la escena y la imagen que se quiere detectar. Este método comparativo, denominado correlación óptica, aprovecha las propiedades de las lentes y su capacidad para realizar transformadas de Fourier. Los dispositivos utilizados para realizar la correlación óptica reciben el nombre genérico de correladores. La investigación realizada tiene como objetivo principal el estudio de los efectos que las aberraciones de los sistemas ópticos presentes en los correladores provocan en el proceso de reconocimiento. Para realizar este análisis se ha desarrollado un método de cálculo de la aberración de onda de un sistema óptico con simetría de revolución y un objeto puntual situado sobre el eje óptico. Este método utiliza el trazado exacto de rayos y las relaciones existentes entre la aberración de rayo y la aberración de onda. Se basa también en la teoría de formación de imagen de Abbe-Rayleigh, la cuál agrupa todos los efectos difractivos en las pupilas del sistema, bien en la de entrada o en la de salida, y utiliza la óptica geométrica para describir la propagación de la luz entre ambas. La fiabilidad del método se ha contrastado experimentalmente mediante técnicas interferómetricas, y se han comparado los resultados para la aberración de onda con los calculados por programas comerciales de diseño y evaluación de sistemas ópticos. Una vez garantizado el correcto funcionamiento de los algoritmos de cálculo, se han analizado dos arquitecturas clásicas de correlación: el correlador de transformadas conjuntas monobanco y el correlador convergente de Vander Lugt. En el primero de ellos se ha realizado un estudio independiente de la influencia de la aberración de cada uno de los difractómetros que lo forman en la correlación final, y a partir de los resultados obtenidos se propone un método de optimización del correlador. Este estudio también se ha realizado para el correlador de Vander Lugt, con resultados similares. En el caso de este segundo correlador también se ha estudiado la inclusión de la información sobre la aberración de ambas etapas del correlador en el diseño de los filtros. Finalmente, basándose en los resultados obtenidos, se propone una nueva configuración que mejora de forma sustancial el comportamiento del mismo como equipo de reconocimiento de formas, llegando a anular completamente la influencia de la aberración., [eng] The aim of this work is to study the influence of the aberrations in optical correlators, and how they affect the correlation peak heights. In order to perform it, a numerical method has been developed. This method calculates the wave aberration of a symmetrical optical system with a point source located at the optical axis. The evaluation of the wave aberration is carried out by means of an exact ray-tracing algorithm which computes the aberration at the different points of the exit pupil according to the relations between wave aberration and ray aberration. Lenses and other stops in the system are assumed to be large enough not to significantly cut the wave front so that light propagation can be accurately described by geometrical optics from the light source to the exit pupil (Abbe-Rayleigh theory of image formation). The method has been experimentally validated by means of interferometric techniques, and the results for the wave aberration have been compared to those calculated by a standard optical design software. Once the right behavior of the algorithm has been guaranteed, two main correlation architectures have been analized: the converging joint transform correlator (JTC) and the converging Vander Lugt correlator (VdLC). In JTC, three different situations have been explored: we consider the aberration only in the first diffraction stage (generation of power spectrum), then only in the second (transformation of power spectrum into correlation) and finally, in both steps simultaneously. Using the results obtained in this study, a simple optimization method is introduced. This method allows the best working conditions for an optical system to be derived. These three situations have been also analyzed in VdLC, and a similar influence from each stage has been found. The correlation process in this architecture uses complex filters, which are usually generated from the image to be detected, free from aberrations. In this part, filters have been designed including information about the aberrations of the optical systems. Finally, a new arrangement which improves the correlation process and cancels the influence of the aberration is proposed.

A search is performed for the central exclusive production of pairs of charmonia produced in proton-proton collisions. Using data corresponding to an integrated luminosity of $3{\rm\ fb}^{-1}$ collected at centre-of-mass energies of 7 and 8 TeV, $J/\psi J/\psi$ and $J/\psi\psi(2S)$ pairs are observed, which have been produced in the absence of any other activity inside the LHCb acceptance that is sensitive to charged particles in the pseudorapidity ranges $(-3.5,-1.5)$ and $(1.5,5.0)$. Searches are also performed for pairs of P-wave charmonia and limits are set on their production. The cross-sections for these processes, where the dimeson system has a rapidity between 2.0 and 4.5, are measured to be $$ \begin{array}{rl} \sigma^{J/\psi J/\psi} &= 58\pm10{(\rm stat)} \pm 6{(\rm syst)} {\rm\ pb} , \\ \sigma^{J/\psi\psi(2S)} &= 63 ^{+27}_{-18}{(\rm stat)}\pm 10{(\rm syst)} {\rm\ pb} , \\ \sigma^{\psi(2S)\psi(2S)} &< 237 {\rm\ pb}, \\ \sigma^{\chi_{c0}\chi_{c0}} &< 69 {\rm\ nb}, \\ \sigma^{\chi_{c1}\chi_{c1}} &< 45 {\rm\ pb}, \\ \sigma^{\chi_{c2}\chi_{c2}} &< 141 {\rm\ pb}, \\ \end{array} $$ where the upper limits are set at the 90% confidence level. The measured $J/\psi J/\psi$ and $J/\psi\psi(2S)$ cross-sections are consistent with theoretical expectations., Comment: 21 pages, 5 figures

We develop a method for generating focused vector beams with circular polarization at any transverse plane. Based on the Richards-Wolf vector model, we derive analytical expressions to describe the propagation of these set of beams near the focal area. Since the polarization and the amplitude of the input beam are not uniform, an interferometric system capable of generating spatially-variant polarized beams has to be used. In particular, this wavefront is manipulated by means of spatial light modulators displaying computer generated holograms and subsequently focused using a high numerical aperture objective lens. Experimental results using a NA = 0.85 system are provided: irradiance and Stokes images of the focused field at different planes near the focal plane are presented and compared with those obtained by numerical simulation.

La teoria general del camp electromagnèetic marca l'entorn adequat per a la formulació i interpretació de fenòmens on intervé la llum. Aquesta teoria admet una considerable simplificació quan es descriuen situacions en les quals es pot negligir el caràcter vectorial dels camps. D'entre aquestes, destaca la difracció, sempre que l'observació es realitzi a distancies molt més grans que la longitud d'ona de la llum que es faci servir. La teoria escalar prediu que la distribució d'intensitats que enregistraria un detector, quan la distancia entre aquest i l'obertura difractant fos proa gran (condicions de difracció de Fraunhofer), és proporcional al mòdul al quadrat de la transformada de Fourier de l'objecte

In this work, the application of the feedback formulation to study several objects that have been attached to form a bigger scatterer is presented. With this technique, a large obstacle can be segmented in several ones and the scattered field can be computed as the result of the multiple interactions among these parts. The results obtained for large scatterers are shown.

A set of algorithms and procedures to compute radar cross section (RCS) of aircraft are presented. The aircraft will be defined by a solid modelling data base. The hardware capabilities of a 3-D graphics accelerator will be used to obtain high-frequency approximation to RCS in real time. We are also developing new algorithms to approach efficiently the electromagnetic problem of scattering by large conducting bodies.

[spa] A finales del siglo pasado Abbe y Rayleigh observaron que los fenómenos de difracción limitaban el poder resolutivo de los instrumentos ópticos. La teoría clásica de aberraciones justificaba también el valor finito del poder separador, y durante mucho tiempo el único método para comparar instrumentos se reducía a la observación de ciertos objetos prefijados que actuaban como test de prueba. Los investigadores cada vez fueron aceptando con más convicción que para determinar la calidad de la imagen óptica era necesario adoptar criterios que tuvieran en cuenta las aberraciones ópticas del sistema, los efectos de difracción producidos a través de los diafragmas y que ofrecieran más datos acerca de la estructura de la imagen. Con el empleo de los tests de barras se ganó más terreno en la información de la imagen óptica, pero fueron Frieser en 1938 y más tarde Selwyn quienes propusieron la utilización. de tests sinusoidales, que pocos años después serían muy útiles para efectuar la medida de la función de transmisión. Hoy existen gran cantidad de criterios de calidad, pero nadie duda y es de aceptación general que la función de transmisión óptica es el método más adecuado para describir el comportamiento físico global de un sistema óptico. El examen de todas estas consideraciones motiva el desarrollo de este trabajo, que consistirá en elaborar una técnica sencilla de la medida del módulo de la función de transmi sión policromática (MFTP) que tendrá en cuenta que el receptor final del conjunto sistema fotográfico y película será el ojo humano,que en definitiva es quien juzgará la calidad de la imagen óptica. Este trabajo de investigación complementará el estudio de la imagen óptica y la evaluación de su calidad llevados a cabo por otros trabajos realizados en este Departamento.

PURPOSE. The study evaluated—theoretically and experimentally—the longitudinal chromatic aberration (LCA) and through-focus energy efficiency (TF-EE) of diffractive–refractive bifocal intraocular lenses (2f-IOLs). METHODS. Four aspheric 2f-IOLs (Tecnis þ4.00 diopter [D] ZMA00, þ2.75 D ZKB00, and AcrySof þ4.0 D SN6AD3, þ2.5 D SV25T0) of same base power 30 D, but different design, additional (add) power, and different material, were tested in vitro in terms of TF-EE when illuminated by 3 red (kR ¼ 625 nm), green (kG ¼ 530 nm), and blue (kB ¼ 455 nm) lights. The LCA affecting the distance and near foci was derived theoretically and measured experimentally from the contributions of the IOLs’ refractive and diffractive powers. Longitudinal chromatic aberration was evaluated in a pseudophakic schematic eye. RESULTS. The distance focus of all 2f-IOLs showed lower energy efficiency (EE) for the blue than for the red light. AcrySof IOLs showed the largest amount of positive LCA in the distance focus that, combined with corneal LCA, would increase the resulting distance LCA in a pseudophakic eye. The near focus of all 2f-IOLs showed higher EE for the blue than for the red light. Better compensation for the LCA of a pseudophakic eye at near focus is obtained with Tecnis than with AcrySof 2f-IOLs. CONCLUSIONS. The energy distribution between the foci of diffractive 2f-IOLs depends on the lens design, the illumination wavelength, and to a lesser extent, the add power. In distance vision, 2f-IOLs’ refractive base power increases the positive LCA of prior ocular media, and the resulting LCA may even surpass the natural LCA of human eye. In near vision, however, the achromatizing effect of diffractive 2f-IOLs may compensate, in part, the natural eye’s LCA

Se establecen las condiciones criticas que necesariamente tienen que cumplirse cuando se pretende calcular las constantes Opticas (n v k) de un material opaco, mediante las mediciones de reflectancia en dos medios de distinto ndice de refraccion.

Electromagnetic scattering of several dielectric objects is computed by a method which uses a feedback formulation to model multiple interactions between scatterers and expreses incident and scattered fields as sums of cylindrical modes, which results in small matrix sizes. The obtained results are shown and compared with the obtained ones with usual techniques.

El objetivo fundamental de este trabajo es modificar el diseño clásico del interferómetro de difracción por punto para que permita medir simultáneamente las curvaturas locales de la fase de una onda en distintos puntos de un plano transversal a la dirección de propagación de un haz de luz con aberraciones. Para ello, y como segundo objetivo, propondremos un método de cálculo nuevo y sencillo que nos permitirá diseñar el componente fundamental del interferómetro para cada aplicación deseada.

Thermal analysis, powder diffraction, and Raman scattering as a function of the temperature were carried out on K2BeF4. Moreover, the crystal structure was determined at 293 K from powder diffraction. The compound shows a transition from Pna21 to Pnam space group at 921 K with a transition enthalpy of 5 kJ/mol. The transition is assumed to be first order because the compound shows metastability. Structurally and spectroscopically the transition is similar to those observed in (NH4)2SO4, which suggests that the low-temperature phase is ferroelectric. In order to confirm it, the spontaneous polarization has been computed using an ionic model.

Laser diffraction (LD) and static image analysis (SIA) of rectangular particles [United States Pharmacopeia, USP30-NF25, General Chapter , Optical Miroscopy.] have been systematically studied. To rule out sample dispersion and particle orientation as the root cause of differences in size distribution profiles, we immobilize powder samples on a glass plate by means of a dry disperser. For a defined region of the glass plate, we measure the diffraction pattern as induced by the dispersed particles, and the 2D dimensions of the individual particles using LD and optical microscopy, respectively. We demonstrate a correlation between LD and SIA, with the scattering intensity of the individual particles as the dominant factor. In theory, the scattering intensity is related to the square of the projected area of both spherical and rectangular particles. In traditional LD the size distribution profile is dominated by the maximum projected area of the particles (A). The diffraction diameters of a rectangular particle with length L and breadth B as measured by the LD instrument approximately correspond to spheres of diameter OL and OB respectively. Differences in the scattering intensity between spherical and rectangular particles suggest that the contribution made to the overall LD volume probability distribution by each rectangular particle is proportional to A2/L and A2/B. Accordingly, for rectangular particles the scattering intensity weighted diffraction diameter (SIWDD) explains an overestimation of their shortest dimension and an underestimation of their longest dimension. This study analyzes various samples of particles whose length ranges from approximately 10 to 1000 μm. The correlation we demonstrate between LD and SIA can be used to improve validation of LD methods based on SIA data for a variety of pharmaceutical powders all with a different rectangular particle size and shape.

Copyright 2015 AIP Publishing. This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. An approach to switching between different patterns of light beams transmitted through the woodpile photonic crystals filled with liquid crystals is proposed. The phase transition between the nematic and isotropic liquid crystal states leads to an observable variation of the spatial pattern transmitted through the photonic structure. The transmission profiles in the nematic phase also show polarization sensibility due to refractive index dependence on the field polarization. The experimental results are consistent with a numerical calculation by Finite Difference Time Domain method.

The light distribution among the far, intermediate and near foci of a new trifocal intraocular lens (IOL) is experimentally determined, as a function of the pupil size, from image analysis. The concept of focus energy efficiency is introduced because, in addition to the theoretical diffraction efficiency of the focus, it accounts for other factors that are naturally presented in the human eye such as the level of spherical aberration (SA) upon the IOL, light scattering at the diffractive steps or the depth of focus. The trifocal IOL is tested in-vitro in two eye models: the aberration-free ISO model, and a so called modified-ISO one that uses an artificial cornea with positive spherical SA in instead. The SA upon the IOL is measured with a Hartmann-Shack sensor and compared to the values of theoretical eye models. The results show, for large pupils, a notorious reduction of the energy efficiency of the far and near foci of the trifocal IOL due to two facts: the level of SA upon the IOL is larger than the value the lens is able to compensate for and there is significant light scattering at the diffractive steps. On the other hand, the energy efficiency of the intermediate focus for small pupils is enhanced by the contribution of the extended depth of focus of the near and far foci. Thus, while IOLs manufacturers tend to provide just the theoretical diffraction efficiency of the foci to show which would be the performance of the lens in terms of light distribution among the foci, our results put into evidence that this is better described by using the energy efficiency of the foci.

The construction of fractal generalized zone plates (FraGZPs) from a set of periodic diffractive optical elements with circular symmetry is proposed. This allows us to increase the number of foci of a conventional fractal zone plate (FraZP), keeping the self-similarity property within the axial irradiance. The focusing properties of these fractal diffractive optical elements for points not only along but also in the close vicinity of the optical axis are investigated. In both cases analytical expressions for the irradiance are derived. Numerical simulations of the energetic efficiency of FraGZPs under plane wave illumination are carried out. In addition, some effects on the axial irradiance caused by the variation in area of their transparent rings are shown., Submitted to Optics Express, 2008