Light field image processing : overview and research issues

Light field (LF) imaging first appeared in the computer graphics community with the goal of photorealistic 3D rendering [1]. Motivated by a variety of potential applications in various domains (e.g., computational photography, augmented reality, light field microscopy, medical imaging, 3D robotic, particle image velocimetry), imaging from real light fields has recently gained in popularity, both at the research and industrial level.peer-reviewe

MODELLING WATER AND ENERGY BALANCE OF THE LAND-ATMOSPHERE SYSTEM USING HIGH RESOLUTION REMOTE SENSING DATA

La rilevanza assunta dal risparmio della risorsa idrica negli ultimi anni ha spinto verso una corretta quanti cazione delle perdite legate al processo evapotraspirativo, al ne di una gestione parsimoniosa della risorsa stessa. In particolare nei sistemi agricoli soggetti a stress severo, sia la misura che la stima dell'evapotraspirazione (ET) ad un'adeguata risoluzione spaziale e temporale sono uno dei principali problemi da a rontare per la comunit a scienti ca. Recentemente, le tecniche di telerilevamento sono divenute un ulteriore strumento a supporto della modellistica idrologica distribuita; in particolare, le immagini acquisite nelle onde corte e nell'infrarosso termico risultano essere di notevole interesse. In questo contesto, i due scopi principali di questa ricerca sono stati: la quanti cazione dell'accuratezza delle misure micro-meteorologiche in sistemi agricoli vegetati con colture alte e sparse; e l'analisi dei modelli basati su dati telerilevati per la stima di ET ad alta risoluzione spaziale e temporale. L'area di studio e caratterizzata da un tipico clima Mediterraneo e da colture olivicole, e si trova localizzata nei pressi di Castelvetrano (Italia). Quest'area e stata oggetto nella primavera-estate 2008 di una campagna di misura mediante istallazioni eddy covariance e scintillometrica, e, contestualmente, dall'acquisizione di 7 immagini multi-spettrali ad alta risoluzione. L'analisi delle misure micro-meteorologiche ha permesso di quanti care l'accordo tra le due tecniche e ha portato allo sviluppo di un nuovo approccio di calibrazione dei dati scintillometrici. Inoltre, alcune ipotesi alla base della stima dei ussi giornalieri sono state discusse in dettaglio. L'analisi degli algoritmi per la simulazione dei processi di scambio nel continuo suolo-pianta-atmosfera e stata focalizzata: i) sulle stime hot-spot di ET mediante un approccio di bilancio energetico residuale, ii) sulla stima in continuo di ET alla scala di campo mediante diversi approcci. Quest'ultima analisi ha evidenziato i buoni risultati del modello accoppiato energetico/idrologico per la stima dei ussi di acqua ed energia sia a scala oraria che giornaliera. In ne, l'applicabilit a di due approcci di data assimilation e stata testata utilizzando sia osservazioni arti ciali che reali.In view of the increased relevance of water saving issues in the last decades, the correct quanti cation of water loss due to evapotranspirative process became fundamental for a parsimonious management of this resource. Especially in agricultural systems subjected to severe water stress, both the measurement and the modelling of evapotranspiration (ET) at adequate temporal and spatial resolution, are important topics for the hydrologist scienti c community. Recently, the remote sensing techniques provide an additional tool to support the hydrologic spatially distributed models; in particular, images acquired in the short-wave and the thermal spectral regions have quite interesting applications. Within this framework, the two principal aims of this work were: to quantify the accuracy of surface energy uxes measured by micro-meteorological techniques in sparse tall vegetated system; and to analyze the capability of remote sensing-based approach to retrieve ET at high temporal and spatial resolution. The selected test site was an area characterized by Mediterranean climate and olive crops, located near Castelvetrano (Italy). This area, during the spring-summer period in 2008, was interested by in-situ measurements campaigns with eddy covariance and scintillometer instruments, and, contextually, by the acquisition of 7 high resolution multi-spectral images. The analysis of micro-meteorological measurements allows to evaluate the agreement between these techniques in the study site, also by means of a novel algorithm for the elaboration of scintillometer data. Moreover, some fundamental hypothesis of daily uxes estimation was critically discussed. The analysis of the algorithms for the simulation of the exchange processes in the continuum soil-plant-atmosphere was focused on: i) the retrieval of hot-spot ET maps by means of residual energy balance approach and ii) the continuous ET estimation at eld scale using di erent approaches. This latter analysis highlights the good performance of a coupled energy/hydrological model for the assessment of energy and water uxes at both hourly and daily scale. Finally, the applicability of two data assimilation schemes was tested using both arti cial and real observations

Efficient and Accurate Disparity Estimation from MLA-Based Plenoptic Cameras

This manuscript focuses on the processing images from microlens-array based plenoptic cameras. These cameras enable the capturing of the light field in a single shot, recording a greater amount of information with respect to conventional cameras, allowing to develop a whole new set of applications. However, the enhanced information introduces additional challenges and results in higher computational effort. For one, the image is composed of thousand of micro-lens images, making it an unusual case for standard image processing algorithms. Secondly, the disparity information has to be estimated from those micro-images to create a conventional image and a three-dimensional representation. Therefore, the work in thesis is devoted to analyse and propose methodologies to deal with plenoptic images. A full framework for plenoptic cameras has been built, including the contributions described in this thesis. A blur-aware calibration method to model a plenoptic camera, an optimization method to accurately select the best microlenses combination, an overview of the different types of plenoptic cameras and their representation. Datasets consisting of both real and synthetic images have been used to create a benchmark for different disparity estimation algorithm and to inspect the behaviour of disparity under different compression rates. A robust depth estimation approach has been developed for light field microscopy and image of biological samples