La Funció de transmissió òptica policromàtica i la seva aplicació en l'avaluació de la qualitat d'imatge d'un instrument fotogràfic

En aquest treball s'estudia la utilitat pràctica d'una sèrie de criteris de qualitat d'imatge basats en el mòdul de la funció de transferència policromàtica (MFTP) del sistema opto-fotogràfic que la forma. Alguns criteris es basen en l'àrea determinada per la corba del MFTP (calculada per a objectes que solament varien en una direcció: test de barres, test sinusoïdal, escletxa) i els eixos de coordenades. També es consideren criteris basats en l'autèntica funció MFTP bidimensional(transformada de Fourier de la funció d'extensió del punt) aquests resulten especialment indicats per a l'avaluació de la qualitat d'imatge en zones de camp de l'instrument.The validity of a series of criteria for evaluating image quality based on the modulus of the polychromatic optical transfer function (PMTF) of the image-forming instrument is studied. The criteria are based on the area determined by the coordinate axes on the curve of the one-dimensional PMTF (calculated for objects varying only in one direction: bar test, sinusoïdal test, slit). Quality criteria based on the two-dimensional character of the actual PMTF function (the Fourier transform of the point-spread function) are also proposed; these are specially suitable for image evaluation in off-axis zones of the instrument

Ray tracing and scalar diffraction calculations of wavefronts, caustics and complex amplitudes in optical systems

The procedures for precise calculation of wavefronts, caustics and complex amplitudes in optical systems are developed. Numerical methods are compared with analytical formulae for caustics. The conditions for the validity of the integration on wavefronts for obtaining the complex amplitudes (and hence intensities defining the PSFs) within scalar diffraction theory are discussed in detail. To illustrate the precision of the results obtained with the developed techniques, an experiment showing quite unexpected results is studied and explained in detail

Computer-aided procedure for optimization of layer thickness uniformity in thermal evaporation physical vapor deposition chambers for lens coating

A computer-aided method to improve the thickness uniformity attainable when coating multiple substrates inside a thermal evaporation physical vapor deposition unit is presented. The study is developed for the classical spherical (dome-shaped) calotte and also for a plane sector reversible holder setup. This second arrangement is very useful for coating both sides of the substrate, such as antireflection multilayers on lenses. The design of static correcting shutters for both kinds of configurations is also discussed. Some results of using the method are presented as an illustration

Optical forces induced by metal nanoparticle clusters

The strong field localization generated between closely placed metal particles excited by electromagnetic radiation induces intense forces on small polarizable objects. In this study we investigate the optical forces that can be generated in the vicinity of metal nanoparticle clusters using fully electrodynamic numerical simulations. The influence of the cluster configuration as well as of the excitation parameters is analyzed

Dark modes and Fano resonances in plasmonic clusters excited by cylindrical vector beams

Control of the polarization distribution of light allows tailoring the electromagnetic response of plasmonic particles. By rigorously extending the generalized multiparticle Mie theory, we show that focused cylindrical vector beams (CVB) can be used to efficiently excite dark plasmon modes in nanoparticle clusters. In addition to the small radiative damping and large field enhancement associated to dark modes, excitation with CVB can give place to unusual phenomenology like the formation of electromagnetic cold spots and the generation of Fano resonances in highly symmetric clusters. Overall, the results show the potential of CVB to tailor the plasmonic response of nanoparticle clusters in a unique way

Funció de transmissió óptica policromàtica i criteris de qualitat vàlids per a instruments fotogràfics comercials

[cat] En aquesta tesi s’ha desenvolupat un mètode de mesura de la funció de transmissió òptica policromàtica d’instruments fotogràfics (sistema constituït per la lent formadora de la imatge i la placa de registre fotogràfic). S’han plantejat una sèrie de criteris de qualitat d’imatge deduïts a partir d’aquesta funció, en estudiar la seva validesa en l’avaluació d’instruments fotogràfics de tipus comercial, per comparació amb valoracions de qualitat establertes per diversos observador

Procedures for the measurement of the extinction cross section of one particle using a Gaussian beam

Two procedures for the measurement of the extinction cross section (ECS) of one particle using a slightly focused Gaussian beam have been introduced and numerically tested. While the first one relies on previously introduced ideas and has close connection with the optical theorem, the second procedure is new and is mostly related with light measurements where the detector collects much of the energy of the incident beam. Both procedures prove to be valid and somehow complementary up to particle sizes of the order of the beam waist, thus enlarging the capability of simple measurement set-ups based on Gaussian beams for the estimation of the ECS of one particle

Design and implementation of a scene-dependent dynamically selfadaptable wavefront coding imaging system

A computational imaging system based on wavefront coding is presented. Wavefront coding provides an extension of the depth-of-field at the expense of a slight reduction of image quality. This trade-off results from the amount of coding used. By using spatial light modulators, a flexible coding is achieved which permits it to be increased or decreased as needed. In this paper a computational method is proposed for evaluating the output of a wavefront coding imaging system equipped with a spatial light modulator, with the aim of thus making it possible to implement the most suitable coding strength for a given scene. This is achieved in an unsupervised manner, thus the whole system acts as a dynamically selfadaptable imaging system. The program presented here controls the spatial light modulator and the camera, and also processes the images in a synchronised way in order to implement the dynamic system in real time. A prototype of the system was implemented in the laboratory and illustrative examples of the performance are reported in this paper

Mueller matrix polarimetry with 3D integral imaging

In this paper, we introduce the Mueller matrix imaging concepts for 3D Integral Imaging Polarimetry. The Mueller matrix of a complex scene is measured and estimated with 3D integral imaging. This information can be used to analyze the complex polarimetric behavior of any 3D scene. In particular, we show that the degree of polarization can be estimated at any selected plane for any arbitrary synthetic illumination source which may be difficult to produce in practice. This tool might open new perspectives for polarimetric analysis in the 3D domain. Also, we illustrate that 2D polarimetric images are noisier than 3D reconstructed polarimetric integral imaging. To the best of our knowledge, this is the first report on Mueller matrix polarimetry in 3D Integral Imaging

Estimation of Degree of Polarization in low light using truncated Poisson distribution

The Degree of Polarization (DoP) of a light beam inside a medium contains unique information about the medium. 3D imaging techniques constitute an optimal procedure for determining the DoP under low light conditions, as the computational reconstruction process can increase the signal-to-noise ratio of the detected light. The definition of the DoP contains a division by the total number of detected photons from the sensor. However, under photon starved conditions, the number of detected photons at a single time period may be equal to zero. This may pose a division by zero problem for the computation of DoP. In this work, we consider a truncated Poisson distribution to overcome this problem and show that the mean value of the computed DoP goes to zero independently of the state of polarization of the light. The validity of our approach is verified by capturing the light fields of a test object to compute its DoP under low light conditions. The formulae derived in this work can be used to correct the deviation of the mean value of the DoP with respect to the ideal measurements