Tesis sobre el tema "LED APPLICATIONS"

Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2007.
Includes bibliographical references.
In the 21st century, mankind faces problem of energy crisis through depletion of fossil fuels as well as global warning through the production of excessive greenhouse gases. Hence, there is an urgent need to look for new sources of renewable energy or ways to utilize energy more effectively. Solid state lighting (SSL) is a major area of research interest to use energy in a more efficient manner. Early light emitting devices (LEDs) were originally limited their use for low power indication lights. Later research produces high brightness LEDs (HB-LEDs) as well as blue color LEDs. This brings to reality of the entire visible light spectrum. White light is also made possible. As with other technologies, numerous obstacles will have to be surmounted in bringing LEDs from the laboratory to the marketplace. LEDs will also have to compete with established technologies such as incandescent and fluorescent lighting. This thesis will describe the current state of high powered LEDs, examine challenges faced by LEDs and look at future markets. Evaluation in the potential of LEDs for general illumination will be carried out through cost modeling and performance analysis.
by Ken, Li Fung Yuen.
M.Eng.

Trivalent rare earth cations (RE3+) activated nanometre-sized Y2O2S and Gd2O2S phosphors were prepared by converting hydroxycarbonate precursor powders during a firing process. The precursors were prepared using the urea homoprecipitation method. The choice of host crystal and dopant were optimised to meet the specific requirements for practical applications in the field of lighting, X-ray detection, and displays. Parameters that affect the luminescent properties of the resulting phosphors, such as doping concentration, excitation mechanism, firing temperature, and host lattice were investigated. Tb3+ and Er3+ co-doped Y2O2S and Gd2O2S were studied for their upconversion properties under 632.8 nm red laser excitation. The intensities of UC emission were affected by both doping concentration and host lattices. Tb3+ and Er3+ co-doped Y2O2S was found to show strong downconversion from Tb3+ and upconversion from Er3+. The presence of the Er3+ cations directly affects the Tb3+ down-converting properties by acting as centres for energy transfer. The possible energy transfer between Gd3+ and Er3+ should be responsible for the different trend of Er3+ upconversion intensity in Y2O2S and Gd2O2S. It has been established that the Tb3+ and Er3+ co-doped system is superior than the Yb3+ and Er3+ co-doped one. In the latter system the presence of Yb3+ reduces the efficiency of both upconversion and downconversion emission under red laser excitation. These phosphors show potential applications in the security and anti-fraud field. The novel ZnS:Mn QDs were prepared and successfully incorporated into GaN based photonic crystal (PC) holes to efficiently produce white light. The crystal structure and luminescent properties of the ZnS:Mn QDs were investigated as well as the factors affecting the filling rate. Zn1-xCdxS:Mn QDs were also investigated. The addition of Cd cations leads to a red shift in the PL excitation spectra of the Zn1-xCdxS:Mn QDs. The crystal structures and surface properties were also affected by the presence of Cd. Monodisperse PbS QDs with particle size of ~5 nm has been obtained using a similar aqueous reaction method.

Mestrado em Engenharia Eletrónica e Telecomunicações
The ever growing energy consumption trends and its impact on the environment has triggered worldwide attention. This has motivated several measures, such as the Kyoto protocol, or the 20 20 20 European strategy, aiming at the reduction of energy consumption. Globally, these measures defend a better and efficient usage of the available energy. This in turn is strongly linked to public awareness and the introduction of efficient electronic equipment. Public street lighting is a good example of these trends, where both aspects are of the utmost importance. The introduction of power LEDs as future lighting devices has motivated several advances coping with these strategies. On one side, LEDs are able to deliver higher efficiency when compared to conventional lighting devices. This has triggered the replacement of old style luminaires by LED based ones. However, their high cost has prevented full adoption and at the present stage, is acting as a slowing down force against this replacement trend. Better solutions are under research on the framework of several European projects. Power LEDs are solid-state devices able to support fast switching, a feature which was not fully supported by conventional lighting devices. Combining this feature with environmental sensing and intelligent control may lead to better power savings. A simple approach would be to consider the that the actual lighting demands depend on the street usage and surrounding lighting levels. For this purpose, the combination of twilight sensors, motion detectors and intelligent control schemes may provide a suitable approach. This way, the real lighting demands can be effectively taken into consideration, providing luminaires able to consume the least possible energy. For this to become a reality several challenges have to be addressed. One of the most important challenges is the LED driver design. Modern lighting systems based on LEDs, replace the traditional ballasts by LED drivers. When efficiency is a major concern, such as in public street lighting, these drivers have to be designed in order to be the most robust and efficient as possible. Recurring solutions resort to switched mode power supplies, able to support light dimming. One of the major problems with these drivers is the fact that their efficiency decreases for lower dimming levels. This is of the utmost importance for public street lighting, as most of the time during night, the luminaires are on a low lighting level (as changes to high lighting conditions depend on street usage). Thus, in order to promote better power savings, the efficiency of the driver should be high for both lighting conditions. Commercially available drivers, exhibit efficiencies on the 90% range for the high lighting conditions, with only 40% to 60% under the low lighting. On the framework of this master dissertation it was investigated the problem of LED driver design aiming at the highest possible uniformity of the efficiency curve, under different loading and dimming conditions. The selected approach was based on quasi-resonant flyback converter, backed up by an active power factor correcting block. The designed driver supports remote configuration and monitoring as well as sensor integration. The archived results show that this driver achieves a peak efficiency of 93% under maximum load and 100% duty-cycle. The efficiency for low dimming conditions (10% duty-cycle) achieves 75%.
As tendências de consumo de energia cada vez maior e seu impacto sobre o meio ambiente tem captado a atenção a nível mundial. Isso tem motivado várias medidas, tais como o Protocolo de Quioto, ou a estratégia Europeia 20 20 20, visando a redução do consumo de energia. Globalmente, estas medidas defendem um uso melhor e eficiente da energia disponível. Este, por sua vez, está fortemente ligado à consciência pública e à introdução de equipamento eletrónico eficiente. A iluminação pública é um bom exemplo dessas tendências, em que ambos os aspetos são de extrema importância. A introdução de LEDs como dispositivos de iluminação tem motivado vários avanços que lidam com essas estratégias. De um lado, os LEDs são capazes de oferecer uma maior eficiência quando comparados com dispositivos de iluminação convencionais. Isso provocou a substituição de luminárias convencionais por luminárias baseadas em LED. No entanto, o custo elevado destes dispositivos tem impedido a adoção plena e na fase atual, está mesmo a atuar como uma força negativa contra esta tendência de substituição. Melhores soluções estão sob investigação no âmbito de vários projetos europeus. Os LEDs são dispositivos de estado sólido, capazes de suportar a comutação rápida, uma característica que não é totalmente suportada por dispositivos de iluminação convencionais. Combinando esta característica com sensores ambientais e controlo inteligente pode-se ambicionar melhores poupanças energéticas. Uma abordagem simples seria a de considerar o que as exigências de iluminação reais dependem do uso das ruas e os níveis de iluminação circundantes. Para este efeito, a combinação de sensores de crepúsculo, detetores de movimento e regimes de controlo inteligentes podem propiciar uma abordagem adequada. Desta forma, os requisitos reais de iluminação podem ser efetivamente considerados, fornecendo luminárias capazes de consumir apenas a energia necessária. Para que isto se torne uma realidade vários desafios têm de ser vencidos. Um dos desafios mais importantes é o projeto LED driver. Nos sistemas de iluminação modernos baseados em LEDs, substitui-se os balastros convencionais por LED drivers. Quando a eficiência é importante, como no caso da iluminação pública, O LED driver têm de ser concebido de forma a ser o mais robusto e eficiente possível. Soluções recorrentes usam a fontes de alimentação comutadas, capazes de suportar o escurecimento adaptativo do fluxo luminoso. Um dos problemas principais no projeto destes drivers é o facto de a sua eficiência diminuir para níveis de regulação mais baixos. Isto é de extrema importância para a iluminação pública, pois na maioria dos casos durante a noite, as luminárias estão num nível de iluminação de baixo. Assim, com a finalidade de promover uma melhor economia de energia, a eficiência do driver deve ser elevada para ambas as condições de iluminação. Drivers comercialmente disponíveis, exibem eficácias na gama de 90% com elevado fluxo luminoso, e apenas 40% a 60% na condição de baixo fluxo luminoso. No âmbito desta dissertação de mestrado foi investigado o problema do projeto de driver LED visando a maior uniformidade possível da curva de eficiência, sob diferentes condições de carga e de fluxo luminoso. A abordagem escolhida foi baseada no conversor flyback quasi-ressonante, apoiado por um bloco de correção de fator de potência ativa. O driver projetado suporta configuração e monitorização remota, bem como de integração de sensores. Os resultados alcançados mostram que este driver atinge um pico de eficiência de 93% na condição de carga máxima e máximo fluxo luminoso. A eficiência em condições de baixo fluxo luminoso é superior a 75%.

Cette thèse de doctorat porte sur les fluctuations temporelles du flux lumineux des lampes LED, ce phénomène portant le nom de papilottement (flicker). Le papillotement est habituellement considéré comme une perturbation en raison de son impact négatif sur la santé. Pour les systèmes d'éclairage à base de diodes électroluminescentes (LED), sa définition vient d'être formalisée dans la norme IEEE 1789:2015 et a été décrite pour les appareils alimentés en courant alternatif (CA). Ce papillotement alternatif résulte des interactions entre l'impédance du réseau, l'onde de tension, les courants harmoniques et le convertisseur de courant alternatif en courant continu (CA - CC). L'alimentation en courant continu est généralement obtenue via des convertisseurs à découpage. Par conséquent, les mêmes facteurs perturbateurs sont également présents sur les réseaux à courant continu. Cette thèse résume les diférences entre les propriétés caractéristiques du papillotement sous alimentation en CA et en CC. Il a été montré dans la littérature et aussi dans cette thèse qu'avec les LED, le facteur clé qui affecte le papillotement réside dans la conception du driver de LED - une partie indispensable des systèmes d'éclairage à LED. Cette thèse décrit une méthodologie d'évaluation de la sensibilité au papillotement des lampes LED sous alimentation en CC et analyse la façon dont cette sensibilité se modifie lorsque les drivers de LED sont simplifiés et adaptés à des alimentations CC. La thèse présente un ensemble d'expériences de mesure visant à déterminer la réaction typique du papillotement des lampes LED à la fois sous alimentation CA et CC. D'autres expériences ont été efectuées pour révéler l'impact de l'adaptation du driver à l'alimentation CC (en enlevant le pont redresseur à diodes). On constate que certaines lampes présentent une meilleure résistance au papillotement, tandis que d'autres lampes présentent une moindre résistance. Ces expériences sont accompagnées de simulations de drivers pour les lampes LED visant à reproduire et à expliquer les résultats des mesures. La thèse décrit en outre une expérience de mesure visant à montrer la sévérité typique de la variation de tension dans un réseau CC à basse tension couplé au CA domestique et son impact sur le papillotement. On conclut qu'un tel système est suisamment robuste pour filtrer les perturbations provenant du CA, mais une interaction indésirable entre la lampe et l'alimentation peut se produire
This dissertation thesis is concerned with temporal fluctuations of the luminous flux of LED lamps, a phenomenon referred to as flicker. Flicker is usually regarded as a disturbance due to its negative impact on human health. For lighting systems based on light emitting diodes (LED), its definition has recently been formalised in norm IEEE 1789-2015 and has been documented on devices supplied with AC voltage. AC flicker results from interactions between network impedance, voltage and current harmonics, and the AC to DC converter. DC supplies are generally obtained by switching converters. Consequently, the same perturbing factors are present on DC networks. The thesis summarises the differences between the characteristic properties of flicker under AC and DC supplies. It has been shown in the literature and also in this thesis that the key factor affecting flicker with LEDs is the design of the LED driver-a necessary part of the LED lighting systems. This thesis describes a methodology for the evaluation of the flicker sensitivity of DC supplied LED lamps and analyses how the sensitivity changes when the LED drivers are simplified and accustomed to DC supply. The thesis presents a set of measurement experiments aimed to determine the typical flicker response of LED lamps both under AC and DC supply. Further experiments were performed to reveal the impact of accustomising the driver to the DC supply (removing the diode rectifier). It was found that some lamps show better flicker immunity while other lamps show worse flicker immunity. These experiments are accompanied by LED driver simulations aiming to reproduce and explain the measurement results. The thesis further describes a measurement experiment aimed to show the typical severity of the voltage fluctuation in a low voltage DC network coupled to AC mains and its impact on the flicker. It is concluded that such a system is robust enough to filter out any perturbations coming from the AC supply, but an undesired interaction between the lamp and the supply may occur

Billions of people use biomass burning cookstoves in their homes and suffer serious health repercussions. Additionally, global warming is exacerbated by cookstove emissions containing greenhouse gases and particulate matter. Improved cookstoves (ICSs) mitigate the problem, but accurate and affordable emission gas measurements, particularly of Carbon Dioxide (CO2) and Carbon Monoxide (CO), are required in order to confidently declare ICSs cleaner burning than traditional cookstoves. The aim of this research is to assess the suitability of photoacoustic (PA) CO2 detection technology for cookstove emissions monitoring. The designs of several longitudinally resonant, photoacoustic, LED, CO2 sensors of varying levels of functionality are presented. Three aluminum cell designs allowed the detection of a photoacoustic signal: a 4cm long cylinder with a ~1cm diameter (Design 3), a 3.9cm long cylindrical resonator with ~1in diameter and quarter-acoustic-wavelength buffer volumes (Designs 4a,b), and a 3.7cm long cylinder with ~1in diameter (Design 5). All three cell designs operate in the longitudinal resonant mode via the irradiation of gases inside the PA cell with a 4.3um wavelength LED, driven at an on-off frequency in the kHz range by a square wave from an Arduino. A rudimentary lock-in amplifier (LIA) based on the AD630 was considered, but the SR830 LIA was actually used to extract the desired MEMS microphone signal from noise. Designs 3-4b produced PA signals dominated by wall-absorption, but the final design (Design 5) yielded a resonant PA signal proportional to CO2 concentration. It was discovered that photoacoustic gas detection is challenging to design and set up without extensive experience and equipment. Practical lessons learned are shared. Primary limitations with the presented designs are identified as the extremely low power of the 4.3um LEDs, wall absorption due to insufficient collimation of LED radiation, dependence on temperature, and reliance on an expensive, high performance, lock-in amplifier. Further testing and development of designs like Design 5 (short cylinder with large diameter-to-length ratio) is necessary to evaluate their potential for in-field, real-time CO2 concentration measurement. Though LED PA CO2 sensing was demonstrated to be possible, it is concluded that NDIR CO2 sensors are currently better suited for cookstove use. In addition to photoacoustic detection, a method of detecting CO2 concentration by measuring resonant frequency of the gas cell (The Acoustic Method) is presented.

Thesis: M. Eng., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2012.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 109-110).
Light Emitting Diodes (LEDs) are a very promising technology for developing more efficient lighting. For high-efficiency applications, a switching current regulator is necessary to control the power drawn by an LED string. This thesis investigates a merged two-stage LED driver for lighting applications, with a switched capacitor (SC) voltage preregulator and a HF resonant-transition inverted buck current regulator. The design, analysis and implementation of the HF stage are developed in detail, and a full merged two-stage system is implimented based on a SC stage pulled heavily from the work of Seungbum Lim.
by John Ranson.
M. Eng.

The thesis is aimed at the investigation of niche applications of solid-state lighting with controllable colour-rendition, spatial, photochemical, and photobiological properties. In order to employ the controllability of light emitting diode (LED) based lighting technology, the research on such niche applications as artwork illumination and street lighting are focussed. The smart colour rendition engine (CRE), which allows for continuously tuning metameric spectra with different colour rendition properties, is introduced. The results on the subjective validation of the statistical colour rendition metric using the CRE are presented. The main requirements for artwork illumination are overviewed and the application of the intelligently controlled CRE in artwork illumination is investigated in two aspects: a) the establishment of subjective needs in colour quality of illumination as a function of the contents of artworks and the observers’ cultural background and b) the effect of the control of photochemical damage irradiance on the visual impression from artworks, while adjusting the chromaticity and colour rendition properties of the illuminant. The results on the optimization of the luminance distribution within an intelligent lighting installation for pedestrian areas using the identification of subjective impressions are presented. The low-circadian action LED source for outdoor lighting is introduced and the results on the assessment of photometric, colorimetric... [to full text]
Ši disertacija yra skirta ištirti kietakūnio apšvietimo su valdomomis spalvų perteikimo, erdvinėmis, fotocheminėmis ir fotobiologinėmis savybėmis galimus nišinius taikymus. Kaip nišinių taikymų pavyzdžiai, kuriuose ryškiausiai atsiskleidžia valdomo apšvietimo privalumai, buvo pasirinkti dailės kūrinių apšvietimas ir gatvių apšvietimas. Šiame darbe pristatytas išmanusis spalvų perteikimo variklis (SPV), leidžiantis tolydžiai keisti metamerinius spektrinės galios skirstinius, pasižyminčius skirtingomis spalvų perteikimo savybėmis. Naudojant SPV validuotas statistinis apšvietimo spalvinės kokybės vertinimo metodas. Apžvelgti dailės kūrinių apšvietimo reikalavimai bei pristatomi SPV pritaikymo dailės kūrinių apšvietimui pagal du kriterijus tyrimai: a) įvertinant apšvietimo spalvinei kokybei teikiamos subjektyvios pirmenybės priklausomybę nuo dailės kūrinio turinio ir žiūrovų kultūrinės kilmės; b) parodant regimosios išraiškos pokytį, atsirandantį dėl apšvietos lygio kitimo, kuomet fiksuojama apšvietimo fotocheminė įtaka apšviečiantiems paviršiams, kintant kokybiniams apšvietimo parametrams. Pristatomi apšvietimo skirstinio pėsčiųjų zonai optimizavimo rezultatai, gauti įvertinus subjektyvius poreikius. Pasiūlytas žemo cirkadinio poveikio kietakūnis šviesos šaltinis, skirtas lauko apšvietimui. Įvertintos tokio šaltinio fotometrinės, kolorimetrinės, spalvų perteikimo, fotobiologinės ir šviesinės taršos savybės bei atlikti tyrimai, įvertinantys psichofizines savybes.

This work targeted the growth of gadolinium (Gd)-doped gallium nitride (GaN) thin films (Ga₁₋ₓGdₓN) by metal organic chemical vapor deposition (MOCVD). Characterization and evaluation of these Ga₁₋ₓGdₓN thin films for application in spintronics/optoelectronics devices also formed part of this work. This work presents: (1) the first report of stable, reproducible n- and p-type Ga₁₋ₓGdₓN thin films by MOCVD; (2) the first Ga₁₋ₓGdₓN p-n diode structure; and (3) the first report of a room temperature spin-polarized LED using a Ga₁₋ₓGdₓN spin injection layer. The Ga₁₋ₓGdₓN thin films grown in this work were electrically conductive, and co-doping them with Silicon (Si) or Magnesium (Mg) resulted in n-type and p-type materials, respectively. All the materials and structures grown in this work, including the Ga₁₋ₓGdₓN-based p-n diode and spin polarized LED, were characterized for their structural, optical, electrical and magnetic properties. The spin-polarized LED gave spin polarization ratio of 22% and systematic variation of this ratio at room temperature with external magnetic field was observed.

In this study, silicon nanocrystals (NC) were synthesized in silicon dioxide matrix by ion implantation followed by high temperature annealing. Annealing temperature and duration were varied to study their effect on the nanocrystal formation and optical properties. Implantation of silicon ions was performed with different energy and dose depending on the oxide thickness on the silicon substrate. Before device fabrication, photoluminescence (PL) measurement was performed for each sample. From PL measurement it was observed that, PL emission depends on nanocrystal size determined by the parameters of implantation and annealing process. The peak position of PL emission was found to shifts toward higher wavelength when the dose of implanted Si increased. Two PL emission bands were observed in most cases. PL emission around 800 nm originated from Si NC in oxide matrix. Other emissions can be attributed to the luminescent defects in oxide or oxide/NC interface. In order to see electroluminescence properties Light Emitting Devices (LED) were fabricated by using metal oxide semiconductor structure, current-voltage (I-V) and electroluminescence (EL) measurements were conducted. I-V results revealed that, current passing through device depends on both implanted Si dose and annealing parameters. Current increases with increasing dose as one might expect due to the increased amount of defects in the matrix. The current however decreases with increasing annealing temperature and duration, which imply that, NC in oxide behave like a well controlled trap level for charge transport. From EL measurements, few differences were observed between EL and PL results. These differences can be attributed to the different excitation and emission mechanisms in PL and EL process. Upon comparision, EL emission was found to be inefficient due to the asymmetric charge injection from substrate and top contact. Peak position of EL emission was blue shifted with respect to PL one, and approached towards PL peak position as applied voltage increased. From the results of the EL measurements, EL emission mechanisms was attributed to tunneling of electron hole pairs from top contact and substrate to NC via oxide barrier.

Chief topic of a Master’s Thesis is comparing of conventional sources of light with LED diodes, their characteristics. This work deals with utilizing LED diodes in automotive lighting, in railway applications and universal information about principle of lighting. Else this work describes feasibility study of headlight of railway locomotive. Emphasis is laying for clearness of this work.

Lighting installations are usually static and based on long-standing visual indicators such as colour temperature, colour rendering, and illuminance values. However, we now know that spectral variations in light elicit non-visual effects via a distinct pathway in our brain, and it is important for designers and architects to take these into account: light influences our mood, modulates our attention, can suppress the production of melatonin and can shift our circadian rhythms. Considering all the spectral aspects of light is the initial step towards designing healthier environments that are both pleasant and respectful to our biology. Multi-channel LED light engines can provide the core technology for a truly spectral lighting design, thereby enabling wider applications of light with different purposes. This dissertation aims at facilitating this transition by delivering cost-effective multi-channel LED light engines capable of generating arbitrary spectral shapes. In the first part of this work, we develop a light engine for a research-oriented market and explore novel designs and solutions for an advanced industrial device aimed at tackling a more general lighting market. These two efforts led to the development of two optically and spectrally different devices: the SPECTRA TUNE LAB light engine (with an on-board spectrometer and ten different LED channels), and the VEGA 07 light engine (equipped with a colour sensor and seven different LED channels). Second, to generate arbitrary spectral shapes, we perform an extensive study on different heuristic algorithms implemented directly in the microcontroller of the light engine as well as in its control software. We show that the simulated annealing algorithm provides fast computation times with excellent spectral fidelity. Third, we develop two types of optical feedback controllers with different light sensors to prevent temperature-driven colour and spectral shifts, and the wear-out of the LEDs. Both these sensors, i.e. the spectrometer in the SPECTRA TUNE LAB and the colour sensor in the VEGA 07, are used to ensure high precision and accuracy of the emitted light at all times and for any kind of target spectrum. Finally, we demonstrate the ways in which these devices can be used for different applications, thereby verifying the huge advantages and added value of this technology as compared to traditional lighting systems. Our developed light engines were installed in the intensive care units of two hospitals (Hospital Vall d'Hebron and Hospital Clínic in Barcelona), in office settings (ARUP's office in London), and 24/7 control rooms (Repsol's refinery control room in Tarragona), among others.
Les instal·lacions dil·luminació solen ser estàtiques i basades en indicadors visuals clàssics com la temperatura de color, la representació dels colors o els nivells d'il·luminació. Tanmateix, avui sabem que la llum també té una funció que no és propiament visual i que els arquitectes i dissenyadors haurien de començar a tenir en compte: la llum pot influir en el nostre estat d'ànim, modular la nostra atenció, regular la producció de melatonina o modificar els ritmes circadiaris. Tenir en compte totes les propietats espectrals de la llum és el primer pas per dissenyar entorns més sans i respectuosos amb la nostra biologia. Així, el disseny i desenvolupament de noves fonts de llum LED multicanal assequibles serà la tecnologia que permetrà un autentic canvi de paradigma espectral i començar a utilitzar la llum per a múltiples aplicacions. Aquest treball té com a objectiu facilitar aquesta transició proporcionant fonts de llum LED amb capacitat per generar qualsevol tipus de forma espectral. En una primera part, hem desenvolupat un sistema d'il·luminació multicanal orientat a un mercat d'investigació i recerca, i hem explorat nous dissenys i solucions per a un dispositiu més industrial amb l'objectiu de penetrar al mercat d'il·luminació general. Els dos esforços s'han materialitzat en dos dispositius òpticament i espectralment diferents: el sistema de llum SPECTRA TUNE LAB (amb un espectròmetre a l'interior i 10 canals LED diferents) i el sistema de llum VEGA 07 (amb un colorímetre i 7 canals LED diferents). En segon lloc, per poder crear qualsevol tipus de forma espectral, hem estudiat diferents algorismes heurístics implementats directament al micro-controlador de la lluminària o en un programari extern. L'algorisme desenvolupat de simulated annealing ha resultat ser el més ràpid amb una fidelitat espectral excel·lent. En tercer lloc, hem desenvolupat dos tipus de controladors òptics de llaç tancat amb dos sensors de llum diferents per evitar canvis de color i canvis espectrals degut a increments de la temperatura o degradació dels LEDs. Ambdós sensors, l'espectròmetre per l'SPECTRA TUNE LAB i el colorímetre pel VEGA 07, s'utilitzen per assegurar que la llum emesa romangui precisa i estable en tot moment, per a qualsevol espectre que vulguem generar. Finalment, demostrem com aquests dispositius es poden utilitzar per a diferents aplicacions oferint grans avantatges en comparació amb sistemes tradicionals. El nostre sistema d'il·luminació s'ha instal·lat a la unitat de cures intensives dhospitals (a l'Hospital Vall d'Hebron i a l'Hospital Clínic, a Barcelona), en entorns d'oficina (a ARUP, a Londres) o en sales de control 24 hores (a la sala de control de la refineria de Repsol, a Tarragona), entre d'altres
Enginyeria òptica

Recently extensive efforts have been spent in order to achieve all silicon based photonic devices exploiting the efficient light emission from nanostructured silicon systems. In this thesis, silicon based nanostructures have been investigated for electro-optical and photovoltaic applications. The thesis focused on three application areas of silicon nanostructures: Light emitting diode (LED), light modulation using quantum confined Stark effect (QCSE) and photovoltaic applications. In the context of LED applications, ZnO nanocrystal/silicon heterojunctions were investigated. Contrary to observation of pure ultraviolet photoluminescence (PL) from ZnO nanocrystals that were synthesized through vapor liquid solidification (VLS) method, visible emissions were observed in the electroluminescence (EL) due to defect states of ZnO. The discrepancy between these emissions could be ascribed to both change in excitation mechanisms and the defect formation on ZnO nanocrystals surface during device fabrication steps. EL properties of silicon nanocrystals embedded in SiO2 matrix were also systematically studied with and without Tb doping. Turn-on voltage of the Tb doped LED structures was reduced below 10 V for the first time. Clear observation of QCSE has been demonstrated for the first time in Si nanocrystals embedded in SiO2 through systematic PL measurements under external electric field. Temperature and size dependence of QCSE measurements were consistently supported by our theoretical calculations using linear combination of bulk Bloch bands (LCBB) as the expansion basis. We have managed to modulate the exciton energy as high as 80 meV with field strength below MV/cm. Our study could be a starting point for fabrication of electro-optical modulators in futures for all silicon based photonic applications. In the last part of the thesis, formation kinetics of silicon nanowires arrays using a solution based novel technique called as metal assisted etching (MAE) has been systematically studied over large area silicon wafers. In parametric studies good control over nanowire formation was provided. Silicon nanowires were tested as an antireflective layer for industrial size solar cell applications. It was shown that with further improvements in surface passivation and contact formation, silicon nanowires could be utilized in very efficient silicon solar cells.

Dépistage du VIH, test de grossesse, mais également surveillance des eaux, détection de contaminants agro-alimentaires : la biodétection est au coeur des problématiques de santé actuelles. Dans ce contexte, les biocapteurs plasmoniques connaissent depuis quelques années un essor particulièrement important : de plus en plus de sociétés, telles que HORIBA Scientific, proposent des prototypes commerciaux, destinés tant à des utilisateurs du domaine de la recherche que de l'industrie. Basée sur le phénomène de résonance des plasmons de surface (communément appelé SPR) la biodétection plasmonique repose sur l'extrême sensibilité d’une onde évanescente se propageant à l’interface entre un film d’or, la biopuce, et le milieu diélectrique couvrant, siège des interactions biomoléculaires étudiées. De manière plus concrète, toute adsorption de matériel biologique se produisant à cette interface entraîne une modification importante des propriétés optiques d’un faisceau de lumière réfléchi par la biopuce : le principe de transduction par SPR consiste alors à mesurer directement ces variations. A l'heure actuelle, différents modes d'interrogation, offrant des performances intéressantes, mais également des limitations propres à chaque configuration. Pour répondre aux exigences de précision et de dynamique de mesure posées par de nombreuses applications, un développement théorique et instrumental, présenté dans ce document, a été initié dans le but de proposer un nouveau un nouveau mode d'interrogation des biopuces plasmoniques : l'interrogation multi-spectrale. Les résultats obtenus par cette technique ont été exploités pour concevoir et réaliser une source multi-spectrale à base de LEDs, particulièrement avantageuse vis-à-vis des configurations existant à l'heure actuelle. La caractérisation du système développé dans le cadre du diagnostic génétique (mucoviscidose) et celui du cancer, ouvre la voie à une nouvelle génération de biocapteurs performants, compacts et de coût relativement raisonnable, présentant un potentiel industriel certain
Biodetection is at the core of the current health concerns, as shown through the variety of applications to HIV screening, food contaminant analysis or water quality monitoring. In this field, plasmonic biosensing is a well-established label-free technique on the market: commercial systems from HORIBA Scientific are currently available for both research and industrial users.Based on the surface plasmon resonance (SPR) phenomenon, plasmonic biodetection uses the high sensitivity of an evanescent wave propagating along a metallic film (forming the biochip) and the surrounding dielectric medium interface. More specifically, the adsorption of biomolecules onto the metal surface induces a strong change in the optical properties of a light beam reflected by the biochip: the main principle of plasmonic transduction consists in measuring these physical changes. Several interrogation techniques have therefore been developed to access such optical information, but they fail in meeting the most demanding user requirements for precise, real-time, high-throughput measurement.Initiated by these issues, the instrumentation work presented in this document has led to the development of a novel SPR interrogation technique, referred to as multi-spectral interrogation. Moreover, the promising results obtained have been pushed forward to propose a multi-spectral illumination system based on LEDs, providing attractive performances compared to existing configurations. The biosensing potential of the developed system, demonstrated through applications to genetic diagnosis and cancer detection, opens the door to a new generation of compact, high-performance, low-cost SPR sensors

The aim of this paper is to develop a new composite structure of catadioptric optical system containing both freeform refractive surface and freeform total internal reflective (TIR) surface for LED road illumination applications. The role of freeform refractive part is to generate the shifted general rectangular illumination pattern to optimally match the shape of the road surface. The application of TIR mechanism is aimed to control the stray light in the sidewalk direction of the road luminaire and maximize the efficient energy efficiency. In this paper, we use the "double pole" ray mapping technique to design the refractive optical surface and the theta-phi coordinate ray mapping technique to derive the freeform TIR surface. The simulation shows that the novel catadioptric design has relatively high collection efficiency, thus high average illuminance level inside the effective illumination area. This lens also has good control of stray light on the backside of the road luminaire. (c) 2017 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

In recent years, high brightness light emitting diodes (HBLEDs) have increasingly attracted the interest of both industrial manufacturers and academic research community. Among the several aspects that make LED technology so attractive, the most appreciated characteristics are related to their robustness, high efficiency, small size, easy dimming capability, long lifetime, very short switch-on/switch-off times and mercury free manufacturing. Even if all such qualities would seem to give to solid state lighting a clear advantage over all the other kinds of competing technologies, the issues deriving from the need of LED technology improvement, on one hand, and of the development of suitable electronic ballasts to properly drive such solid state light sources, on the other, have so far hindered the expected practical applications. The latter problem, in particular, is nowadays considered the main bottleneck in view of a widespread diffusion of solid state technology in the general lighting market, as a suitable replacement of the still dominant solutions, namely halogen and fluorescent lamps. In fact, if it is true that some aspects of the devices’ technology (e.g. temperature dependent performance, light quality, efficiency droop, high price per lumen, etc…) still need further improvements, it is now generally recognized that one of the key requirements, for a large scale spread of solid state lighting, is the optimization of the driver. In particular, the most important specifications for a LED lamp ballast are: high reliability and efficiency, high power factor, output current regulation, dimming capability, low cost and volume minimization (especially in domestic general lighting applications). From this standpoint, the main goal is, therefore, to find out simple switched mode power converter topologies, characterized by reduced component count and low current/voltage stresses, that avoid the use of short lifetime devices like electrolytic capacitors. Moreover, if compactness is a major issue, also soft switching capability becomes mandatory, in order to enable volume minimization of the reactive components by increasing the switching frequency in the range of the hundreds of kHz without significantly affecting converter’s efficiency. It is worth mentioning that, in order to optimize HBLED operation, also other matters, like the lamp thermal management concern, should be properly addressed in order to minimize the stress suffered by the light emitting devices and, consequently, the deterioration of the light quality and of the expected lamp lifetime. However, being this work focused on the issues related to the research of innovative driving solutions, the aforementioned thermal management problems, as also all the topics related to the improvement of solid state devices’ technology, will be left aside. The main goal of the work presented in this thesis is, indeed, to find out, analyze and optimize new suitable topologies, capable of matching the previously described specifications and also of successfully facing the many challenges dictated by the future of general lighting. First of all, a general overview of solid state lighting features, of the state of the art of lighting market and of the main LED driving issues will be provided. After this first introduction, the offline driving concern will be extensively discussed and different ways of approaching the problem, depending on the specific application considered, will be described. The first kind of approach investigated is based on the use of a simple structure relying on a single power conversion stage, capable of concurrently ensuring: compliance with the standards limiting the input current harmonics, regulation of the load current and also galvanic isolation. The constraints deriving from the need to fulfil the EN 61000-3-2 harmonics standard requirements, when using such kind of solution for low power (<15W) LED driving purposes, will be extensively discussed. A low cost, low component count, high switching frequency converter, based on the asymmetrical half bridge flyback topology, has been studied, developed and optimized. The simplicity and high compactness, characterizing this solution, make it a very good option for CFL and bulb replacement applications, in which volume minimization is mandatory in order to reach the goal of placing the whole driving circuitry in the standard E27 sockets. The analysis performed will be presented, together with the design procedure, the simulation outcomes and the different control and optimization techniques that were studied, implemented and tested on the converter's laboratory prototype. Another interesting approach, that will be considered, is based on the use of integrated topologies in which two different power conversion stages are merged by sharing the same power switch and control circuitry. In the resulting converter, power factor correction and LED current regulation are thus performed by two combined semi-stages in which both the input power and the output current have to be managed by the same shared switch. Compared with a conventional two-stages configuration, lower circuit complexity and cost, reduced component count and higher compactness can be achieved through integration, at cost of increased stress levels on the power switch and of losing a degree of freedom in converter design. Galvanic isolation can be provided or not depending on the topologies selected for integration. If non-isolated topologies are considered for both semi-stages, the user safety has to be guaranteed by assuring mechanical isolation throughout the LED lamp case. The issue, deriving from the need of smoothing the pulsating power absorbed from the line while avoiding the use of short lifetime electrolytic capacitors, will be addressed. A set of integrated topologies, used as HBLED lamp power supplies, will be investigated and a generalized analysis will be presented. Their input line voltage ripple attenuation capability will be examined and a general design procedure will be described. Moreover, a novel integrated solution, based on the use of a double buck converter, for an about 15W rated down-lighting application will be presented. The analysis performed, together with converter design and power factor correction concerns will be carefully discussed and the main outcomes of the tests performed at simulation level will be provided. The last kind of approach to be discussed is based on a multi-stage structure that results to be a suitable option for medium power applications, like street lighting, in which compactness is not a major concern. By adopting such kind of solution it is, indeed, possible to optimize converter’s behavior both on line and on load side, thereby guaranteeing both an effective power factor correction at the input and proper current regulation and dimming capability at the output. Galvanic isolation can be provided either by the input or the output stage, resulting in a standard two stage configuration, or by an additional intermediate isolated DC-DC stage (operating in open loop with a constant input/output voltage conversion ratio) that namely turns the AC/DC converter topology into a three stage configuration. The efficiency issue, deriving from the need of multiple energy processing along the path between the utility grid and the LED load, can be effectively addressed thanks to the high flexibility guaranteed by this structure that, relaxing the design constraint, allows to easily optimize each stage. A 150W nominal power rated ballast for street solid state lighting applications, based on the latter (three stage) topology, has been investigated. The analysis performed, the design procedure and the simulations outcomes will be carefully described, as well as the experimental results of the tests made on the implemented laboratory prototype.
Negli ultimi anni i dispositivi LED di potenza ad elevata luminosità (HBLED) hanno attirato in misura sempre crescente l'interesse della comunità scientifica, sia all'interno del mondo accademico che di quello industriale. Tra le varie caratteristiche, che rendono questo tipo di tecnologia interessante, le qualità più apprezzate sono certamente: la robustezza, l'elevata efficienza, le piccole dimensioni, la facilità di modulazione dell'intensità luminosa, il lungo tempo di vita, l'estrema rapidità di accensione e spegnimento e l'assenza di mercurio. Nonostante tutti questi aspetti sembrino dare alla tecnologia a stato solido un netto vantaggio rispetto alle tecnologie concorrenti, l'utilizzo dei LED di potenza nel campo dell'illuminazione rimane a tutt'oggi abbastanza limitato. La necessità di ulteriori progressi nella tecnologia dei dispositivi, da un lato, e dello sviluppo di soluzioni in grado di garantirne il corretto ed efficiente pilotaggio, dall'altro, ne hanno, infatti, fino ad ora frenato la diffusione rispetto alle attese. Quest'ultimo aspetto, in particolare, è al giorno d'oggi considerata il vero "collo di bottiglia" in vista dell'impiego su larga scala della tecnologia a stato solido, in sostituzione delle soluzioni, tutt'ora dominanti nel mercato dell'illuminazione, basate sull'utilizzo di lampade alogene e a fluorescenza. Se, da un lato, infatti, è vero che alcuni aspetti della tecnologia dei dispositivi (e.g. variabilità delle prestazioni con la temperatura, qualità della luce, calo dell'efficienza luminosa con l'aumentare della corrente, elevato costo per lumen, ecc...) necessitano di essere ulteriormente perfezionati, dall'altro è ormai universalmente riconosciuto che l'elemento chiave per l'ampia diffusione dell'illuminazione a stato solido è proprio l'ottimizzazione dello stadio di alimentazione. In particolare, le specifiche più importati che un ballast per lampade a LED è tenuto a soddisfare sono: elevata affidabilità ed efficienza, elevato fattore di potenza, capacità di regolazione della corrente di uscita e di modulazione del flusso luminoso, basso costo e minimo ingombro (soprattutto nell'illuminazione domestica). L'obiettivo principale è, quindi, riuscire ad ideare soluzioni basate sull'utilizzo di topologie semplici, caratterizzate da ridotto numero di componenti e limitati livelli di stress di corrente e tensione, che non prevedano l'impiego di componenti con breve tempo di vita come i condensatori elettrolitici. Inoltre, nelle applicazioni in cui la compattezza è considerata uno degli aspetti di maggior rilievo, anche la capacità di operare in soft-switching diviene una specifica indispensabile. Ciò è infatti necessario al fine di permettere la minimizzazione del volume delle componenti reattive, tramite l'aumento della frequenza di commutazione nel range delle centinaia di kHz, senza compromettere l'efficienza del convertitore. Per completezza, vale la pena di ricordare che, per ottimizzare il funzionamento dei LED ad elevata luminosità, andrebbero presi in considerazione anche altri aspetti, come ad esempio le problematiche legate alla gestione del calore dissipato dalla lampada, importanti al fine di limitare gli stress termici subiti dai dispositivi e, di conseguenza, migliorare la qualità della luce emessa e massimizzare il tempo di vita della lampada. Tuttavia, essendo il lavoro presentato in questa tesi centrato sulle questioni relative allo stadio di alimentazione, i suddetti problemi di gestione termica, come anche gli aspetti relativi allo sviluppo della tecnologia dei dispositivi non verranno esaminati. L'obiettivo principale del lavoro che verrà descritto nel corso dei prossimi capitoli, è, infatti, la ricerca di soluzioni innovative per il pilotaggio da rete elettrica di lampade basate su tecnologia a stato solido. Verranno pertanto approfonditamente trattate le tematiche relative ad analisi, ottimizzazione e sviluppo di topologie che siano in grado di soddisfare i requisiti precedentemente enunciati e di affrontare con successo le sfide proposte dalla continua evoluzione dello scenario del "general lighting". Per prima cosa, sarà fornita una visione di insieme riguardante lo stato dell'arte del mercato dell'illuminazione, le caratteristiche dei dispositivi di illuminazione a stato solido ed i principali aspetti relativi al loro pilotaggio. Dopo questa prima sezione introduttiva, la tematica relativa all'alimentazione da rete elettrica di tali dispositivi verrà approfonditamente discussa. Differenti modi di approcciare il problema, a seconda della specifica applicazione considerata, verranno discussi. Il primo tipo di approccio che verrà esaminato si basa sull'uso di una semplice struttura, formata da un singolo stadio di conversione di potenza. Essa è in grado di fornire al contempo il rispetto degli standard che limitano il contenuto armonico della corrente di ingresso, l'isolamento galvanico e la regolazione della corrente e dell'intensità luminosa in uscita. I vincoli, dettati dall'esigenza di garantire il rispetto della normativa EN 61000-3-2, in applicazioni di bassa potenza (<15W) prive di uno stadio dedicato alla correzione del fattore di potenza, verranno approfonditamente trattati. Saranno, poi, illustrati i risultati dello studio, sviluppo ed ottimizzazione di un convertitore a singolo stadio, operante ad elevata frequenza di commutazione, basato sulla topologia flyback a mezzo ponte asimmetrico. La semplicità, il ridotto numero di componenti ed il basso costo, che caratterizzano tale tipo di soluzione, la rendono adatta all'alimentazione di lampade per il settore residenziale, in cui la compattezza dello stadio di alimentazione è di fondamentale importanza al fine di consentirne l'alloggiamento nei classici socket E27. L'analisi effettuata, la procedura di progetto ed risultati ottenuti in simulazione ed a livello sperimentale durante lo studio di tale topologia verranno accuratamente descritti e discussi. Un altro interessante tipo di approccio che verrà considerato si basa sull'utilizzo di topologie integrate, nelle quali due diversi stadi di conversione vengono uniti tramite la condivisione dello stesso interruttore di potenza e della relativa circuiteria di comando. Nel convertitore che ne risulta, la correzione del fattore di potenza e la regolazione della corrente nei LED saranno dunque garantite dalla combinazione dei due semi-stadi, il cui interruttore comune dovrà essere in grado di gestire sia la potenza di ingresso che la corrente di uscita. Rispetto alla configurazione a due stadi convenzionale, la soluzione ottenuta tramite l'integrazione consente una minore complessità circuitale, un ridotto numero di componenti e, di conseguenza, una maggiore compattezza ed un minor costo. Tutto ciò viene guadagnato a scapito di un maggiore livello di stress nei componenti e della perdita di un grado di libertà nel progetto del convertitore. L'isolamento galvanico può essere garantito o meno a seconda del tipo di topologie che vengono selezionate per l'integrazione. Se la scelta ricade su topologie non isolate, la sicurezza dell'utente andrà comunque garantita isolando meccanicamente l'involucro della lampada. I problemi legati alla necessità di smorzare la componente alternata della potenza assorbita dalla rete, evitando al contempo l'utilizzo di componenti con basso tempo di vita, come i condensatori elettrolitici, verranno discussi. A tal proposito si studieranno le caratteristiche di un insieme di topologie integrate, al fine di fornirne un'analisi ed una procedura di design generalizzate. Se ne esaminerà, inoltre, la capacità di attenuare la componente ondulatoria della tensione di ingresso che viene trasferita al carico, dove si traduce in un'oscillazione della corrente di alimentazione fornita ai LED. Verrà proposta, poi, una soluzione basata su una topologia derivante dall'integrazione di due convertitori di tipo step-down (abbassatori di tensione), per applicazioni di "down-lighting", dimensionata per una potenza di circa 15W. Se ne discuteranno, in particolare, i dettagli di maggiore interesse relativi all'analisi effettuata, alla procedura di progetto ed ai risultati dei test effettuati in ambiente di simulazione. L'ultimo tipo di approccio considerato prevede, infine, l'utilizzo di una topologia multi-stadio, ritenuta una scelta appropriata soprattutto per applicazioni lighting di potenza elevata (>60W), come l'illuminazione stradale, in cui la compattezza dell'alimentatore non è ritenuta un aspetto di primaria importanza. Tramite questo tipo di soluzione è, infatti, possibile ottimizzare le prestazioni del convertitore sia dal lato della rete che dal lato del carico. Si riescono a garantire, in tal modo, un'efficace correzione del fattore di potenza, un adeguato controllo della corrente di uscita ed un'appropriata modulazione del flusso luminoso emesso dalla lampada. L'isolamento galvanico può essere fornito dallo stadio di ingresso o da quello di uscita o da un aggiuntivo stadio DC-DC intermedio, operante a catena aperta con rapporto di conversione di tensione costante. In quest'ultimo caso la struttura del convertitore, si trasforma, dalla classica configurazione a due stadi, in una topologia a triplo stadio. Il problema che nasce dalla necessità di assicurare un elevato livello di efficienza del sistema, nonostante l'interposizione di ripetuti stadi di conversione dell'energia tra la rete ed il carico a LED, può essere efficacemente risolto grazie alla flessibilità che caratterizza tale tipo di struttura. L'aumento del numero dei gradi di libertà in fase progettuale permette, infatti, di ottimizzare con semplicità ogni singolo stadio. Per comprovare limiti e potenzialità di tale tipo di approccio, si è deciso di studiare un ballast (dimensionato per una potenza nominale di 150W) basato sulla topologia a triplo stadio precedentemente menzionata, per applicazioni nell'ambito dell'illuminazione stradale. L'analisi condotta, la procedura di progetto ed i risultati delle simulazioni effettuate verranno discussi nel dettaglio, così come i risultati sperimentali dei test di laboratorio effettuati sul prototipo costruito.

The research in optoelectronics has recently shown impressive advancements, thanks to the development of disruptive technologies, such as Gallium Nitride LEDs and lasers - that are enabling novel lighting devices - and Silicon photonics - that will change the paradigm in broadband data transmission. Industrial laboratories and academic researchers are working towards the improvement of device performance and reliability. This goal is complicated by the complex nature of optoelectronic devices and systems: a deep knowledge on material properties, device characteristics and system optimization is needed to identify the physical mechanisms that limit the lifetime of the devices, and to address possible solutions. The aim of this thesis is to report on a detailed study of the physical factors that limit the performance and reliability of innovative optoelectronic technologies based on nitrides and arsenides. The investigation was conducted by means of purposely planned Accelerated Life Test (ALT) experiments and short-term stress tests on selected state-of-the-art devices, which let us identify the main physical processes responsible for the long-term degradation of the devices, and pinpointed the weaknesses of modern LEDs when temporary operated outside their Safe Operating Area (SOA) as a consequence of Electrical Over-Stress (EOS) events. With regard to Gallium Nitride (GaN)-based white and visible monochromatic LEDs, we found that under constant near-breakdown reverse bias the devices exhibit a time-dependent degradation phenomenon, which promotes the increase of the leakage current of the device, eventually leading to its catastrophic failure. The peculiar failure statistics, as well as the electro-luminescence and leakage-current data acquired during stress, could be interpreted by considering that highly-depleted GaN under reverse bias may behave like a partially-leaking dielectric that degrades over time due to a defect percolation process, similar to the dielectric degradation-driven breakdown process affecting Silicon MOS devices. On the other hand, high forward-current short-term step-stress on high-power LEDs revealed that sustained operation at driving currents above the maximum rating of the devices can rapidly induce failure in correspondence of a major current injection point, dependent on the specific chip structure, as a consequence of the localized power dissipation and temperature reached due to extreme current crowding effects and to the degradation of the conductivity of extended device regions. A clear dependence of the failure mode on the chip structure and device layout could also be found during the investigation on the effects of single short EOS events of increasing amplitude on high-power white LEDs. The experimental data helped identifying the best LED design to be employed in an electrically critical environment, also showing that EOS-related reliability issues tend to arise more from extrinsic elements of the LED system rather than from the semiconductor chip. Unlike High-Brightness (HB) state-of-the-art LEDs, whose main reliability concern is represented by EOS events, cost-effective mid-power LEDs for lighting applications were found to suffer from gradual degradation processes impacting in the long term on both the electrical an optical characteristics of the device. Moreover, the results of the ALTs highlighted the role of the plastic package in the degradation of the optical properties of the emitted light. The long-term reliability of mid-power LEDs was further investigated at system level by performing a lifetime analysis of commercial LED bulbs employing these devices as primary light sources. The increased complexity of the system under stress negatively impacted on the stability over time of the luminous performances of the luminaries, which was severely affected by the degradation of extrinsic elements like the diffusing dome or the current driver. In Part II of this work, our system-level analysis continued with an extensive investigation on the reliability of blue-emitting phosphors for near-UV laser excitation, as part of a research project performed in collaboration with the New Energy and Industrial Technology Development Organization (NEDO), Japan. By means of a series of pure thermal stress experiments and stress under high levels of optical excitation, we have been able to identify the physical process responsible for the degradation of the phosphors under extreme and more conservative operating conditions. In particular, while the phosphors demonstrated good stability during pure thermal treatment in air up to 300 °C, for temperatures equal to or greater than 450 °C the material exhibited a time-dependent drop in the photo-luminescence, which was attributed to the thermally-induced autoionization of the Eu2+ optically active centers. By means of different material characterization techniques, evidence of this degradation process was also found on samples stressed under moderate 3 W/mm2 – 405 nm optical excitation. This indicated that the optically (and thermally) induced ionization of the optically-active species is the most critical degradation process for this family of phosphorescent material. The operating limits of an improved second generation luminescent material were also investigated by means of short term stress under 405 nm optical excitation. The experimental data showed that, for a given deposition condition, a threshold excitation intensity for continuous pumping exists. Above this threshold, decay of the steady-state photo-luminescence performances and degradation of the material were found to take place, which suggested that the material was being operated in an unuseful excitation regime, mainly limited by the thermal management capabilities of the carrier substrate employed for our experimental purposes rather than from intrinsic properties of the phosphor. Part III of this thesis is devoted to the analysis of the degradation processes of heterogeneous III-V/Silicon infrared (IR) laser diodes designed for integrated telecommunications and interconnects. By submitting the devices to a series of constant current stress tests, a gradual degradation of the main device parameters was observed. In particular, in every stress scenario the devices under test showed (i) an increase in the threshold current, (ii) a decrease in the turn-on voltage, and (iii) an increase in the apparent carrier concentration within the space charge region. The variation of the electrical parameters was found to be significantly correlated to the optical degradation for long stress times; the results support the hypothesis that degradation originates from an increase in the non-radiative recombination rate, possibly due to the diffusion of defects towards the active region of the devices. In order to further investigate the physical origin of the diffusing defects, capacitance Deep-Level Transient Spectroscopy (C-DLTS) analysis was performed. The results indicate the presence of several deep levels, with a main trap located around 0.43 eV above the valence band energy. This trap was found to be compatible with an interface defect characteristic of the quaternary material employed to grow the active region of the device.
L'ultimo decennio di ricerca nell'ambito dei dispositivi optoelettronici ha contribuito allo sviluppo e alla successiva introduzione sul mercato di rivoluzionarie tecnologie, sia in ambito illuminotecnico, grazie agli innovativi sistemi di illuminazione basati su LED e laser in Nitruro di Gallio, che in ambito telecomunicazioni, dove la Silicon photonics promette di stravolgere l'odierno approccio alla trasmissione a larga banda. Innumerevoli laboratori di ricerca universitari e privati concorrono nell'incrementare le performance e l'affidabilità dei dispositivi. Tale obbiettivo, tuttavia, è ostacolato dalla complessa natura dei dispositivi optoelettronici e, ancor più, dei sistemi su di essi basati. Una conoscenza approfondita dei materiali, delle proprietà dei dispositivi e dell'ottimizzazione a livello di sistema risultano essere indispensabili per l'identificazione dei meccanismi fisici che limitano il tempo di vita utile dei dispositivi, e per lo sviluppo di possibili soluzioni. Scopo di questa tesi è descrive i risultati di un'estesa analisi finalizzata ad identificare i processi fisici che limitano l'affidabilità e le prestazioni degli innovativi sistemi optoelettronici basati su semiconduttori III-V. Per tale scopo sono stati realizzati specifici esperimenti di degrado accelerato e stress a breve termine su dispositivi allo stato dell'arte, che hanno permesso di individuare i processi fisici responsabili del degrado, graduale o catastrofico, cui possono essere soggetti i moderni dispositivi optoelettronici durante la propria vita operativa. Nello specifico, le analisi condotte su LED ad emissione nel visibile basati su Nitruro di Gallio (GaN) hanno innanzitutto rivelato che la prolungata polarizzazione del dispositivo con tensioni inverse vicine al valore critico di breakdown è accompagnata dall'instaurarsi di un processo di degrado tempo-dipendente che induce l'aumento della corrente di leakage del LED, portandolo eventualmente alla failure catastrofica. La peculiare distribuzione statistica del tempo di failure, unita all'andamento temporale di corrente e segnale di elettro-luminescenza durante lo stress in inversa, sono stati interpretati supponendo che il Nitruro di Gallio, portato in svuotamento spinto dalle elevate tensioni inverse, possa comportarsi come un dielettrico con perdite che degrada nel tempo a causa della percolazione di difetti, con un processo del tutto simile al breakdown tempo-dipendente del dielettrico presente nei MOS in Silicio. Lo studio sugli effetti a breve termine di elevate correnti di polarizzazione su LED in GaN ad alta potenza ha invece evidenziato una localizzazione della failure dei dispositivi in prossimità dei principali punti di iniezione di corrente, specificatamente associabili alla particolare struttura del dispositivo in analisi. Tale tipologia di stress si è inoltre rivelata altamente dannosa anche per la struttura epitassiale del dispositivo, che, a causa delle elevate temperature e densità di corrente in gioco, ha mostrato incrementi di resistività localizzati. Una più marcata dipendenza delle modalità e delle condizioni di failure dalla struttura e dal layout superficiale è emersa dall'analisi degli effetti di eventi di overstress di breve durata su LED bianchi ad alta potenza. I risultati sperimentali hanno portato all'identificazione della tipologia di LED più adeguata da adottare in ambienti soggetti a disturbi elettrici, mostrando inoltre come le problematiche relative ad eventi di overstress elettrico siano determinate più dalle debolezze di elementi estrinseci del LED che dal chip di semiconduttore. L'attività di ricerca ha poi evidenziato come per LED bianchi a media potenza in condizioni operative limite i processi di degrado graduale delle caratteristiche ottiche ed elettriche del dispositivo, ed in particolar modo relativi al package plastico, possano risultare deleteri per l'affidabilità a lungo termine della sorgente allo stato solido. L'analisi affidabilistica su tale tipologia di LED è stata poi estesa a livello di sistema, andando ad investigare i meccanismi di degrado che interessano le comuni lampadine a bulbo basate per l'appunto su LED bianchi a media potenza. La maggiore complessità del sistema illuminante sotto stress ha impattato negativamente sulle performance a lungo termine del bulbo, la cui affidabilità è risultata essere per lo più limitata da elementi estrinseci al LED, quali la cupola diffusiva oppure il driver di corrente. Nella seconda parte di questa tesi sono state analizzate le proprietà affidabilistiche di uno di questi elementi estrinseci: i fosfori. In collaborazione con l'organizzazione per lo sviluppo delle nuove energie e delle tecnologie industriali del Giappone (NEDO), è stata condotta un'estesa ricerca sull'affidabilità di fosfori ad emissione nel blu per eccitazione nel vicino UV tramite sorgenti a stato solido, in particolare laser. Attraverso una serie di stress termici e/o sotto fascio ottico ad elevate intensità, è stato possibile identificare il principale meccanismo fisico responsabile del degrado delle performance di fotoluminescenza del materiale fosforescente in esame. Nello specifico, correlando quest'ultimo fenomeno con le variazioni delle proprietà chimico-fisiche del materiale, è stato possibile identificare nell'autoionizzazione otticamente e/o termicamente indotta dei centri otticamente attivi di Eu2+ la principale causa di degrado del fosforo. La stress ottico a breve termine su pigmento luminescente di seconda generazione ha poi permesso di identificare un valore limite di intensità per il pompaggio ottico continuo. Oltre tale soglia, le performance del materiale luminescente calano per effetto congiunto della perdita di efficienza dovuta alle alte temperature di esercizio e al degrado non reversibile del materiale stesso. Nella terza parte di questa tesi vengono analizzati i meccanismi di degrado di diodi laser IR ibridi basati su semiconduttori III-V e Silicio progettati per sistemi di telecomunicazione e di interconnessione integrati. Esperimenti di degrado accelerato condotti a corrente costante hanno permesso l'identificazione di diversi processi di degrado graduale, tra i quali: (i) l'aumento della corrente di soglia, (ii) la decrescita della tensione di turn-on del diodo (iii) e l'incremento della concentrazione di carica apparente in prossimità della regione attiva. Sulla base della correlazione tra tali processi, è stata formulata l'ipotesi secondo la quale l'origine del degrado ottico del dispositivo risieda nell'aumento del rate di ricombinazione non radiativa, possibilmente dovuto alla diffusione di difetti verso la regione attiva. Al fine di investigare l'origine della specie diffondente sono state impiegate tecniche di analisi spettroscopica che hanno permesso l'identificazione di diversi livelli trappola all'interno del dispositivo, il principale dei quali, localizzato 0.43 eV al di sopra della banda di valenza, è risultato essere compatibile con un difetto d'interfaccia caratteristico del materiale semiconduttore utilizzato per la crescita della regione attiva dei dispositivi in esame.

This work aims at exploring the competing effects of various internal/built-in fields on the electronic structure and optical properties of III-N nanostructured (Quantum Dots and disk-in-a-wire) LEDs using a multiscale modeling approach. The objective is three-fold: (1) calculate the strain distribution, optical transition rates and one-particle electronic states using a 10-band sp3s* tight-binding framework; (2) to compute the effects of piezoelectric and pyroelectric polarization on the optical transition rates; (3) to model piezoelectricity in the wurtzite lattice, we have considered four different polarization models (based on the experimental /bulk and ab initio coefficients) in increased order of accuracy; (4) to study the origin and effects of these four competing internal fields on the electronic structure of self-assembled InN/GaN quantum dots having three different geometries, namely, box, dome, and pyramid; (5) integrating the NEMO3-D with commercial TCAD tool Synopsys to determine the terminal electrical and optical characteristics of InGaN/GaN disk-in-a-wire LEDs; and (6) finally to propose optimum device specifications for InGaN/GaN disk-in-a-wire LEDs to achieve maximum Internal Quantum Efficiency (IQE).

Les lampes à LEDs s’imposent comme la solution d’avenir pour l’éclairage vert de demain. Malgré des durées de vie annoncées par les constructeurs supérieures à 50 000h, une dérive prématurée de la qualité colorimétrique a été constatée. Ce travail de thèse porte sur l’influence de la photodégradation sur les propriétés optiques de l’un des composants d’un module LED : le composite luminescent qui est associé à la puce semi-conductrice. Des composites luminescents ont été élaborés à partir d’une matrice polymère (EVA ou PMMA) et d’un luminophore inorganique : Y3BO6 : 15% Eu3+. L’évolution des propriétés physico-chimiques et optiques de ces composites a été étudiée sous irradiation dans des conditions accélérées (λ>300 nm) et dans les conditions d’usage (LED UV, λ=365 nm). Le luminophore n’a pas montré d’effet prodégradant sur la photooxydation du polymère. Une perte des propriétés optiques du composite sous l’effet de la photodégradation du polymère a été mise en évidence dans le cas de la matrice EVA. L’évolution des paramètres photométriques de la lumière émise par les composites luminescents au cours du photovieillissement a pu être reliée à l’accumulation des photoproduits dans les films. En revanche, pour les composites PMMA/luminophore, la structure chimique et les propriétés optiques de ces composites ne sont pas modifiés pour des durées de photovieillissement accélérés de 4000h
Phosphor-converted LEDs are emerging as an eco-friendly solution for the next generation lighting. Despite lifetimes claimed over 50 000h, a loss of the optical properties was noticed. This work focuses on the influence of photodegradation of the materials on the optical properties of the polymer/phosphor composite that is used to encapsulate the semiconductor chip. Luminescent composites were made from a polymer matrix (EVA or PMMA) and an inorganic phosphor: Y3BO6 :15% Eu3+. The evolution of physical, chemical and optical properties of these composites was investigated under irradiation in accelerated conditions (λ>300 nm) and in the use conditions of UV LED (λ=365 nm). The phosphor showed no pro-degrading effect on the photooxidation of the polymer. A loss of the optical properties of the composite was observed and ascribed to the photodegradation of the polymer in the case of the EVA matrix. The evolution of photometric parameters of the emitted light by the luminescent composite during photoaging can be attributed to the accumulation of photoproducts in films. However, for PMMA/phosphor composites, the chemical structure and optical properties of such composites are kept for accelerated photoaging time up to 4000h

Les composants dédiés et actuellement disponibles pour le marché automobileprésentent une grande diversité technologique tant au niveau puce que stratégie de packaging ouencore architecture module (mono-puce ou multi-puce) pour des performances équivalentes. Cetteétude s’est attachée à développer une méthodologie d’évaluation de la fiabilité de deux filièrestechnologiques particulières de modules de LEDs multi-puce : l’une intègre une technologie verticale(VTF pour Vertical Thin Film) tandis que la seconde est focalisée sur une structure par puce montéeretournée(TFFC pour Thin Film Flip Chip). La méthodologie s’articule autour de trois principaux axes:· La connaissance des structures et le développement de modèles électro-optiques et thermiquesmulti-puce permettant d’extraire les paramètres clés à suivre au travers d’un panel varié detechniques d’analyse physique et non-destructives incluant les aspects électriques, optiques,thermiques….· Une analyse comportementale de robustesse par paliers afin de dégager les margesopérationnelles de fonctionnement ainsi que les modes et les signatures caractéristiques dedéfaillance.· Une étude de fiabilité conduite à partir de différents régimes de contraintes accélérées pourestimer les durées de vie moyennes de ces nouveaux composants en environnement automobileet l’impact au niveau système.Les résultats mettent en évidence une durée de vie très dépendante de la filière technologique(facteur 6 entre les deux filières étudiées). Les analyses de défaillance ont permis d’identifierprécisément les comportements de ces nouvelles sources d’éclairage pour dégager des indicateursprécoces de défaillance. Enfin, des préconisations ont été extraites afin de fiabiliser les futursprojecteurs à sources LEDs de puissance pour les applications en automobile
With rapid development of Lighting Emitting Diode (LED) market, LED performancesare now suitable for automotive high beam / low beam lighting applications. Due to the need of UltraHigh Brightness (UHB-LEDs), LEDs are packaged on high thermal conductivity materials to obtainmultichip module (4 chips in series), which deliver up to 1000 lumens at 1A. Currently, several LEDtechnologies are commercially offered for the same performances, and different packaging strategieshave been implemented in terms of chip configuration, bonding, down conversion phosphor layerand mechanical protection to optimize performances. This study addresses a dedicated methodologyfor reliability analysis, applied on two LED chip packaging technologies: On the one hand, a VerticalThin Film (VTF) technology; on the other hand a Thin Film Flip Chip (TFFC). Our methodology is basedon 3 main items: Packaging technology structure, materials analysis and electro-optical and thermal multichipmodels for both technologies to understand and extract the key parameters to monitor duringageing tests. Robustness assessment tests to define operating margins, adjust accelerated life-testingconditions, and identify failures signatures. Reliability study through a 6 000 hours High Temperature Operating Life (HTOL) acceleratedtests, to predict the Mean Time To Failure (MTTF) of these new light source technologiesregarding the automotive mission profile. Linked to failure analysis, convincing failuremechanisms are proposed.Based on these results, parametric variations are compared to failure analysis results topropose failure mechanisms. The HTOL tests reveal that both LED technologies have their specificreliability behavior and failure modes: catastrophic failure and gradual failure. Predictive lifetimeestimations (L70B50) of these multichip modules give a factor 6 between both technologies.Beyond these reliability results, the multichip architecture brings new issues for Solid StateLighting (SSL) sources in automotive, as well as partial failure or unbalanced behavior after stress.These new issues are discussed through the behavior modeling of a 10 LED modules batch for bothfailure modes. Modeling results demonstrate that the predictive lifetime of a LED multichiparchitecture is directly related with the LED technology failure mode

Nous proposons des liaisons optiques en Silicium à faible coût utilisant des longueurs d'onde de propagation de 650 à 850 nm. La création de circuits intégrés optoélectroniques à grande échelle et de bus de données optiques au sein même des circuits intégrés, utilisant des composés Silicium CMOS, ont été envisagées présentant une voie prometteuse [1] - [3]. Dans les dernières tentatives de réalisation de systèmes optoélectroniques en CMOS, les technologies était principalement orientée sur l'utilisation des longueurs d'onde à 1550 nm [4] - [6], principalement en raison de la facilité de conception et de fabrication des guides d'ondes dans ce régime de longueur d'onde. Cependant, aucune source optique rapide efficace et aucun photo-détecteur Si ne sont disponibles à cette longueur d'onde de 1550 nm. Aujourd'hui, les solutions pour surmonter le problème sont principalement axées sur l'intégration de sources optiques basées sur des éléments du groupe IIIV reportés sur Silicium par liaison moléculaire [7a] - [7b].Si la source optique, le détecteur, les guides d'ondes et les capteurs pouvaient être réalisés sur la même puce CMOS Silicium, par exemple à une longueur d'onde de 750 nm, divers systèmes micro-photoniques sur puces, légers et miniaturisés, pourraient être conçus et réalisés. Alors que les sources optiques au Silicium ne sont peut-être pas encore au niveau de performance requis pour les communications à très haut débit, les systèmes optoélectroniques "tout-Silicium" à faible coût restent encore un excellent point de départ. Ces sources pourraient également conduire à un nouveau champ qui pourrait s'appeler «microsystèmes photoniques Si» ouvrant la voie à de nouvelles applications et produits notamment pour l'optique médicale, biomédicale, les interconnexions optiques et la biophotonique. Ces systèmes ne nécessitent de bande passante à très haute fréquence pour émettre, et les puissances d'émission de nos diodes électroluminescentes (LED) à avalanche peuvent être suffisantes pour assurer le fonctionnement de tels systèmes. Ce travail de thèse de doctorat traite donc des liaisons optiques SiGe / Si à faible coût en utilisant des dispositifs Photonique-Microondes tels que une source à Diode Electro-Luminescente (DEL) à avalanche en Silicium (SiAvLED) et Silicium-Germanium intégrée en technologie bipolaire, des guides d'ondes optiques en Nitrure de Silicium et en Oxyde de Silicium, des phototransistors bipolaires à hétérojonction (HPT) SiGe. Ce travail se concentre sur l'intégration combinée de sources optiques à l'échelle micrométrique, de guides d'ondes optiques et de détecteurs sur une même puce pour former une liaison de communication complète pour diverses applications iv impliquant des liaisons de courte longueur d'onde (750 nm à 950 nm). Les progrès fournis par ce travail par rapport aux travaux antérieurs pourraient être synthétisés comme suit:• La source optique, le guide d'ondes et le détecteur ont tous été intégrés et alignés sur la même puce, dans une technologie industrielle RF bipolaire SiGe 0,35μm, pour former une liaison optique ou optique micro-onde complète sur puce à la longueur d'onde de 750 nm.• Une série de liaisons de communication optique de deuxième génération de 50μm de longueur, utilisant des longueurs d'onde de propagation de 650 à 850 nm, a été conçue et réalisée en technologie SiGe bipolaire également. Des sources optiques, des guides d'ondes et des détecteurs de dimensions micrométriques ont tous été intégrés sur la même puce pour former une communication complète sur les liaisons micro-optiques. Des LED Si à base d'avalanche (Si Av LED), des contacts Schottky, des stratégies de densification TEOS, des guides d'ondes à base de Nitrure de Silicium et des technologies de détection bipolaire SiGe de pointe ont été utilisées comme stratégies de conception clés.• Le logiciel de simulation R-soft (Beam Prop) a été utilisé comme outil de simulation
We propose a low cost full-silicon optical links utilizing 650 – 850 nm propagation wavelengths. The creation of large-scale opto-electronic integrated circuits and optical data “highways” inCMOS integrated circuitry, utilizing Si CMOS compounds, have been envisioned and hold much promise [1] - [3] The latest attempts for realizing optoelectronic systems in CMOS technology have until now mainly been focused on utilizing wavelengths at 1550 nm [4] - [6], mainly because of the ease of design and fabrication of waveguides in this wavelength regime. However, no effective high-speed optical sources and Si detectors are available at this 1550nmwavelength. Today solutions to overcome the problem are mostly focused on the integration of group III-V elements based optical sources on Silicon through molecular bonding [7a] – [7b]. If optical sources, detectors, waveguides, and sensors could be realized on the same Si CMOS chip at, say, 750 nm wavelength, various low power consuming, light and miniature on-chip-based micro-photonic systems can be designed and realized. While Silicon optical sources may not yet be at the required performance level for very-high speed communications, the low cost “all silicon”opto-electronic systems still remain a great grail. These sources could lead as well to new field that could be appropriately named “Si photonic microsystems” opening the route to new sensing applications and products especially for the medical, biomedical optics, optical interconnect and bio-photonics field. These systems also do not require ultrahigh frequency bandwidths to transmit, and the emission powers of our avalanche Si light-emitting diodes(LEDs) may be sufficient to sustain the operation of such systems. This PhD thus deals with low cost SiGe/Si optical links using Microwave-Photonics devices such as, Bipolar integrated SiAvLED, Silicon Nitride and Silicon Oxide optical waveguides, SiGeHPTs, Si and SiGe/Si LEDs. It focuses on the combined integration of micron-scale optical sources, optical waveguides and detectors on the same chip to form a complete communication link for various applications involving short wavelength links (750nm to 950nm). The progress provided by this PhD to previous works could be synthesized as below:• Optical source, waveguide and the detector were all integrated and aligned on the same chip, in an industrial based technology, to form complete on-chip micro-optical links at750nm wavelength, with a SiGe radio frequency (RF) 0.35µm bipolar process.• A series of second generation of on-chip optical communication links of 50µm length, utilizing 650 – 850 nm propagation wavelengths, have been designed and realized inSiGe. Micron dimensioned optical sources, waveguides and detectors were all integrated ion the same chip to form a complete communication on-chip micro-optical links. Avalanche based Si LEDs (Si Av LEDs), Schottky contacting, TEOS densification strategies, Silicon-Nitride based waveguides, and state of the art SiGe bipolar detector technologies were used as key design strategies.• R-soft simulation software (Beam Prop) was used as a mathematical capable simulation tool to model various Silicon-Nitride optical waveguide structures, before the designing, the fabrication, characterization and testing of the device. Various device structures were modeled, simulation iterations were performed on several optical waveguide designed structures before the device design, and the devices were tested experimentally.• Best performances of the designed on-chip optical links show a conversion loss as low as30dB from source to detector with up to 500MHz in cut off frequency. The good alignment and the good efficiency of each device are then clearly achieved. Higher frequency performances are also envisaged from preliminary measurements

La thèse intitulée «Design, Synthesis and SupramolecularArchitectures of New Heterocyclic Compounds with PotentialApplications in Material Chemistry and Photovoltaic Conversion” eststructurée en cinq chapitres traitant de nouveaux: a)cyclopenta[c]pyrannes hétérocyclique; b)des propriétés fluorescentes; d) potentiels dispositifs de l'électroniquemoléculaire; d) donneurs moléculaires pour les photovoltaïquesorganiques et e) carbon‘quantum’dots électroluminescents.Le premier chapitre présente une étude des dérivéspseudoazulenique ayant une unité cyclopenta[porte sur leur synthèse, l'analyse structurale et leur comportement dansdes réactions de substitution électrophile pour obtenir des composésayant des propriétés fluorescentes.Le deuxième chapitre présentediastéréoisomères et l'étude de propriétés de fluorescencedérivés d’indenopyrone.Le troisième chapitre décrit la synthèse des nouvellesarchitectures basées sur l’unité cyclopenta[être modifiés structurellement par l'influence d'un stimulus chimiqueou électrochimique afin d'élaborer des potentiels dispositifs del'électronique moléculaire.Dans le quatrième chapitre, la synthèsedes propriétés électroniques des nouvelles molécucellules solaires organiques (OSC) ontLe cinquième et dernier chapitre décrit la passivation desdéfauts de surface des nanoparticules de carbone avec desmolécules organiques ou des polymères pour obtenir desnanoparticules de carbone photoluminescentse surnommé ‘quantum dots
The thesis entitled “Design, Synthesis and SupramolecularArchitectures of New Heterocyclic Compounds with PotentialApplications in Material Chemistry and Photovoltaic Conversion” isstructured into five chapters concerning new: a) heterocycliccyclopenta[c]pyrans; b) indenopyrone derivatives with fluorescentproperties; c) potential devices of molecular electronics; d)donors for organic photovoltaics and e) electroluminescent carbon‘quantum’ dots.The first chapter presents a study of pseudoazulenederivatives having a cyclopenta[c]pyran unit. The survey comprises thesynthesis, structural analysis and reactivity towards electrophilicsubstitution in order to obtain fluorescent compounds.The second chapter deals with the separation odiastereoisomers and the study of fluorescent propertiesindenopyrone derivatives.The third chapter describes the synthesis of newarchitectures based on cyclopenta[c]pyran unit that can be structurallymodified by the influence of a chemical or electrochemical stimulus inorder to work as potential devices in molecular electronics.In the fourth chapter, the synthesis andelectronic properties of new molecular donors for organic solar cellswas described.The fifth and last chapter outlines the passivation of surfacedefects on carbon nanoparticles using small organic molecules orpolymers in order to obtain photoluminescent carbon nanoparticlesdubbed as carbon‘quantum’dots

This practice based, interaction design project explores how mobile, locative and social web technologies present new opportunities to help community members in need through collaborative online mapping of local support services and information sharing. In collaboration with community organisations, two social and locative media applications were produced. The underlying design principles were generalised to enable community agencies and individuals to apply them in development of further applications that aggregate information for social benefit.

Thesis submitted in fulfilment of the requirements for the degree Doctor of Technology: Design in the Faculty of Informatics and Design at the Cape Peninsula University of Technology 2013
Digital drawing and animation, using basic computer software, opens up new possibilities in creative practice-­‐led research. The digital medium, with its relative ease of reproduction and storage of images, facilitates a reflective method of thinking-­‐while-­‐ drawing, thereby stimulating the creative process and providing a unique means of reflection-­‐in-­‐action. The computer’s ability to record images allows for temporal disruption, providing possibilities for exploring alternative creative solutions as well as retrospective, reflection-­‐on-­‐action. This thesis presents an interrogation of the researcher’s creative practice, as well as the findings and creative artefacts of other relevant practitioners in the field of digital drawing, animation, and related creative activities. A reflexive methodology was used to investigate the relationship between making, doing, and knowing in creative practice. The findings are supported by creative outputs (making), reflection on the creative process in relation to supporting literature (doing), and knowledge resulting from this reflection together with related theoretical research (knowing). The research revealed that digital drawing and animation supports new modes of making resulting in the production of original creative artefacts. It was further revealed that in relation to “doing”, the digital medium supports reflective practice by enabling the creative practitioner to document and reflect on these outputs both during and after making. The resulting reflexive actions combined with theoretical research lead to revelations concerning the relationship between thinking and drawing when using digital media as well as in a broader sense. The study thus contributes insights concerning art and design thinking, and makes a contribution to new developments in visual arts and design research. Practice-­‐led research introduces a theoretical paradigm that has methodological implications particularly in the context of the current re-­‐structuring and transformation of art and design education at South African Universities of Technology. The findings indicate that digital drawing and animation can encourage a critical and reflective approach not only in the work of creative practitioners by supporting new modes of making, but that it also has positive implications for visual arts research and teaching. In this regard the research highlights the need for promoting the integration of theory and practice in visual arts and design education curricula.

This thesis describes the development of electronic modules for fusion neutron spectroscopy as well as several implementations of artificial neural networks (NN) for neutron diagnostics for the Joint European Torus (JET) experimental reactor in England. The electronics projects include the development of two fast light pulser modules based on Light Emitting Diodes (LEDs) for the calibration and stability monitoring of two neutron spectrometers (MPRu and TOFOR) at JET. The particular electronic implementation of the pulsers allowed for operation of the LEDs in the nanosecond time scale, which is typically not well accessible with simpler circuits. Another electronic project consisted of the the development and implementation at JET of 32 high frequency analog signal amplifiers for MPRu. The circuit board layout adopted and the choice of components permitted to achieve bandwidth above 0.5 GHz and low distortion for a wide range of input signals. The successful and continued use of all electronic modules since 2005 until the present day is an indication of their good performance and reliability. The NN applications include pulse shape discrimination (PSD), deconvolution of experimental data and tomographic reconstruction of neutron emissivity profiles for JET. The first study showed that NN can perform neutron/gamma PSD in liquid scintillators significantly better than other conventional techniques, especially for low deposited energy in the detector. The second study demonstrated that NN can be used for statistically efficient deconvolution of neutron energy spectra, with and without parametric neutron spectroscopic models, especially in the region of low counts in the data. The work on tomography provided a simple but effective parametric model for describing neutron emissivity at JET. This was then successfully implemented with NN for fast and automatic tomographic reconstruction of the JET camera data. The fast execution time of NN, i.e. usually in the microsecond time scale, makes the NN applications presented here suitable for real-time data analysis and typically orders of magnitudes faster than other commonly used codes. The results and numerical methods described in this thesis can be applied to other diagnostic instruments and are of relevance for future fusion reactors such as ITER, currently under construction in Cadarache, France.

碩士
吳鳳科技大學
光機電暨材料研究所
102
The main purpose of this study is to develop an LED fixture which collaborates with creative and innovative ideas and design, serves as a replacement of the traditional lighting appliances, and most of all is environment friendly. The two of advantages of LED lighting over conventional lighting are the better energy efficiency and the longer expected lifetime, which significantly lead to the phase out of the traditional ones as the LED technology advances. This thesis explores the performances in power consumption and brightness for various types of LED lamp driver circuits. In determining the availability of the designed LED lamp on multiple appliances, the author carried out a variety of tests and found out that the experimental results meet the general requirements for regular users.

abstract: A novel integrated constant current LED driver design on a single chip is developed in this dissertation. The entire design consists of two sections. The first section is a DC-DC switching regulator (boost regulator) as the frontend power supply; the second section is the constant current LED driver system. In the first section, a pulse width modulated (PWM) peak current mode boost regulator is utilized. The overall boost regulator system and its related sub-cells are explained. Among them, an original error amplifier design, a current sensing circuit and slope compensation circuit are presented. In the second section – the focus of this dissertation – a highly accurate constant current LED driver system design is unveiled. The detailed description of this highly accurate LED driver system and its related sub-cells are presented. A hybrid PWM and linear current modulation scheme to adjust the LED driver output currents is explained. The novel design ideas to improve the LED current accuracy and channel-to-channel output current mismatch are also explained in detail. These ideas include a novel LED driver system architecture utilizing 1) a dynamic current mirror structure and 2) a closed loop structure to keep the feedback loop of the LED driver active all the time during both PWM on-duty and PWM off-duty periods. Inside the LED driver structure, the driving amplifier with a novel slew rate enhancement circuit to dramatically accelerate its response time is also presented.
Dissertation/Thesis
Doctoral Dissertation Electrical Engineering 2016

碩士
崑山科技大學
電子工程研究所
100
LED (Light Emitting Diode) is the lighting market of mainstream.The paper will LED application of detection and its Extended. In the control side,this thesis is a system of FPGA Based digital control platform to order to achieve design of the three control systems: Both color temperature and illumination of the LED detection system. Illumination detection system to implement chip And Luminaries with lighting and communication functions LED.The three control systems are all of the independent individual.

碩士
臺北城市科技大學
資訊應用產業碩士專班
106
ABSTRACT In recent years, LED lighting has gradually been widely used in lighting products, while the traditional incandescent and fluorescent lamps are slowly being replaced by the trend. We uses a single-stage power converter in LED lighting, with small size, high power factor, economical, energy-saving carbon reduction and other advantages. The single-stage converter power supply provides high-precision constant-current mode that reliably stabilizes the current on the LED and allows for uniform LED brightness for improved light quality.

碩士
大葉大學
電機工程學系
103
With the increasing depletion in global energy and greenhouse-effect issues, green energy has attracted the worldwide attention. The research of renewable energy is focused on solar, biomass ethanol, wind power and geothermal. On the other hand, waste heat recovery is the other method for improving energy efficiency. This thesis proposes waste heat recovery of light emitting diode (LED) that utilizes a thermoelectric generator (TEG) to withdraw the waste heat of LED module with a temperature gap between LED module and ambient air and produce DC electricity. The recovered energy can be used to provide a DC fan with heat sink for the active cooling of LED devices. The simulation model is built using MATLAB/Simulink and compared with the measurement results by utilizing LabVIEW-based measurement system. The temperature of LED module can be controlled under . The autonomous and self-sufficient characteristics are demonstrated.

碩士
清雲科技大學
電子工程所
101
In recent years, the rise of the plant factory has promoted the agricultural development in Taiwan. Besides, the illuminant light source of the plant has been gradually replaced by an artificial light source. Because LED is with the advantages such as a small size and low power consumption over the traditional light source, it has been widely used as the artificial light source of the plant factory in the United State of American, Japan, Taiwan, and other countries. In fact, it has been successfully demonstrated that LED provides the necessary light of the growth of the plants, e.g., butterfly orchids, oriental lilies, lettuces, cabbages, strawberries, etc. In the past few decades, there has been attracted much attention on the light source of the plant factory. Among the articles, the researchers almost focused on the effect of light source on the plant growth in wavelength and light intensity. In the thesis, a new method based on optical design is used to improve the lighting way of the plant factory by way of the software named as Advanced System Analysis Program (ASAP). In this research, the parallel light is used as the light source by combining the mining color light, which is formed by using white, red, and blue LEDs, and Fresnel Lens. However, the improved light source is with the merits of power saving compared to the traditional light source. In addition, the light intensity and uniformity can be analyzed by ASAP. Of course, the optimization of the optical model can be also obtained by the improved method. And its feasibility is demonstrated.

碩士
國立雲林科技大學
電機工程系碩士班
101
ABSTRACT This thesis presents a Flyback converter for lighting emitter diode (LED) applications. Instead of traditional light up circuit and Cold Cathode Fluorescent Lamp (CCFL), the LED is popular in lighting industry applications. Flyback converter with the low cost and simple structure is adopted to drive the LED lamp. The LED constant voltage and constant current loop are used to prevent the LED damage clue to the voltage and current variation. Finally, according to the analysis and design consideration in this paper, a convertor with P_o=12W, v_ac=85~265V, v_o=31V was implemented to verify the performance of the proposed converter. Keywords：Flyback converter, Constant voltage control, Constant current control.

博士
國立中央大學
電機工程學系
101
Recently, TFT-LCD is the most popular display application in the flat panel display application. The main parts in the TFT-LCD system includes: LCD panel module, backlight module and electronic driver module. This paper provides the novel design of direct-in backlight module of the TFT-LCD system and the inspection method for the gap mura defect of the LCD panel. We applied the LED light source, secondary light-guide component and micro reflector structure to design the novel backlight module. Compared with West’s work in 2003, the uniformity ratio for our new design shows an increase of 24%, from 60% to 84%, and the luminance a 23.29% improvement, from 10 000 nits to 12 329 nits. On the other hand, we combine the optical interference method and neural network classification to detect the gap mura defect of the LCD panel. Three kinds of mura defects including non-uniformity sealant panel; panel with foreign material and fiber-cluster panel are tested. After learning process of Neural Network Classification method, the Mean Squared Error could decrease less than 0.01. By this method, we could sort out the bad panel and increase the yield rate of the production line.

碩士
國立成功大學
環境工程學系碩博士班
97
Copper (CuO (52%) and Cu2+ (48%)) in chemical mechanical polishing (CMP) wastewater can be effectively enriched with saccharides. In addition to recycling of copper from the CMP wastewater, the core-shell nanoparticles (Cu@C) can be synthesized by carbonization of copper-saccharides complexes. The Cu@C core-shell nanoparticles have been studied to explore potential applications in thermal interface materials (TIMs) and thermal dissipation of CPU and LED as well as photothermal cancer therapy. A simple and inexpensive method for synthesis of M@C (M: Cu, Ni, Ag, bimetallic or alloy metals) with saccharides as the carbon source has been developed. By adjusting C/M ratios, nanosize-controllable metal (Cu) encapsulated in the carbon shells (thickness = 3-5 nm) can be synthesized by carbonization of the metal-starch complexes at 673-773 K. The carbon shells can prevent the nanosize core metal from oxidation and aggregation. Expetimentally, dispersion of a small amount (5%) of the Cu@C nanoparticles (Cu size = 14 nm) in a commercial thermal grease (Y-500), its thermal conductivity can be increased by at least 60%. The smaller (7 nm) or larger (80 nm) Cu in the Cu@C nanoparticles cause an increase of the thermal conductivity by 10-30%. In addition, for the long-time heat-dissipation applications, the shell carbon may consume the residual oxygen (C+O2�彪O2) in the grease and expose the core copper for a better thermal conductivity (391 W/m-K). Kinetic parameters of shrinking of carbon on Cu@C by steam refoming have been obtained. The Arrhenius activation energy (Ea) for shrinking of the carbon on Cu@C with Cu sizes of 7 nm is 165.5 kJ mol-1, which are much less than that (Ea = 240.5 kJ mol-1) of the hollow carbon sphere (H@C) with cage size of 7 nm at 573-973 K. Thermal dissipation of heat pipes can be enhanced with coating of Cu by shrinking of the carbon from Cu@C on the internal surfaces of heat pipes. The photothermal behaviors of metals and alloys encapsulated in carbon shells has been investigated with the NIR laser. The temperature raise of the Cu@C with Cu size of 14 nm under the exposure of an 809 nm Ti sapphire femtosecond laser with the power of 51 W/cm2 is 30 K. The core-shell nanoparticles with an excellent photothermal characteristic have immense potential for photothermal therapy of eradicated malignant tumors.

碩士
國立臺北大學
資通科技產業碩士專班
101
This research presents a multi-channel LED driver for mobile device applications. With regards to the new trend for backlighting applications in mobile electronics and portable devices; requiring a smaller size, lower cost, lesser noise and more accurate current control LED driver is highly desirable, with this the idea of integrating more than one design features within a single chip is advantageous. The analysis of using a capacitor-less low dropout regulator to power the constant current source has been explored, with the implementation of wide range battery voltage of 2.7V to 4.2V. Possible load current variations were introduced and verified to output a fixed voltage of 2.5V. The design ensure a current matching of less than 1% error current balance and achieve a high accuracy current control of less than 1% error regardless with LED’s forward voltage variation. Moreover, for high end portable device with multimedia applications, dimming frequency can be set to 10 KHz. In addition, a switching output is a better approach for managing LED’s contrast and brightness adjustment as well as maximizing power consumption, ensuring longer life for driving string of LEDs. This design is implemented in 0.35um TSMC 2P4M CMOS process and the chip size is 1.89x1.7 mm2.

碩士
國立清華大學
電子工程研究所
94
This thesis work demonstrated the high performance of a light emitting diode (LED) which is able to illuminate visible light at very high lumen (eg. 254 mcd); the LED is formed by five InGaN/GaN quantum wells and a high voltage enduring contacting structure which is composed of Nickel (Ni)/Aluminum doped Zinc Oxide (AZO). In order to enhance the high voltage enduring capability of the LED, one of the contacting structures is formed as a p-i-n structure. By depositing a thick layer of ZnO (i.e. 440 nm) as the i layer of this p-i-n structure, a large portion of voltage is sustained by this i layer, which makes the LED able to increase its voltage tolerance to as high as 65 VDC. Also attributed to the transparent property of the contacting structure, the light emitting capability of this LED demonstrated an unabated one due to the non-transparent electrode; this trait further assures such device as a viable technology solution for tomorrow’s household illuminating devices. With further development on this LED and its processing technology, this LED bears the potential to be directly connected to the household power source -- 110 VAC.

碩士
國立中興大學
材料科學與工程學系所
98
In this thesis, we report an approach for efficiently improving the threading dislocation (TD) density and internal quantum efficiency of InGaN-based near-ultraviolet (~400 nm) light-emitting diodes (LEDs). A combination of selective etching of GaN defects and patterned sapphire substrate (PSS) techniques forms a growth mask of TDs in GaN epitaxial layers. This selective etched-GaN/PSS structure can efficiently achieve defect centralization and the defect density can be reduced to 105 cm-2. The structural properties of the regrown GaN epilayers were investigated in details using double-crystal X-ray diffraction, cathodeluminescence, and secondary ion mass spectroscopy. Under a 350-mA injection current, the output power of the SiO2-block/PSS LED is enhanced by 46% compared with that of the conventional GaN/sapphire one. The improvement of the output power is not only due to the decrease in dislocation density, but also to the enhancement of extraction efficiency using PSS. In addition, we investigate the characteristics of near-ultraviolet (~400 nm) InGaN multiple-quantum well based LED using a SiLENS simulation program. Simulations of light-output power versus current are performed for GaInN/GaN light-emitting diodes grown on GaN-on-sapphire templates with different threading dislocation densities. The energy band diagrams, carrier concentrations, radiative recombination efficiency, light-current curves, and external quantum efficiency are taken into account in detail. Low-defect-density devices exhibit a efficiency peak followed by droop as current increases. However, the high-defect-density devices show low peak efficiencies and little droop. The simulation results suggest that improvement of internal quantum efficiency is mainly due to the increase of radiative recombination at high current injection.

碩士
明道大學
材料與能源工程學系碩士班
104
This research is the imaging lens design combined with LED light pipe, The use of three types of available lens group reached a minimum correction of all aberrations film features combine to make the light guide tube, image is clear and bright as the goal neached, The Lens deaign of three designs can be used for image capture, image capture even further extension of medical uses, such as endoscopy, etc. Simulation to achieve the desired results through Zemax software.Which is the MTF value has reached 0.45@ 40c⁄mm for all fields. Keyword:LED. Lightpipe. Three lens groups. Video shooting. Image Capture

碩士
和春技術學院
電機工程研究所
96
The purpose of this thesis is to investigate the optical and electrical characteristics of high power LEDs under different current and ambient temperature. At the same time, Is Spice software is used to build its model and modulize it. In this thesis, integrating sphere system is used to measure the variation of characteristics of 1W RGB-LED, such as luminous flux, dominant wavelength and equivalent resistance, etc., at the driving current from 100mA to 350mA and ambient temperature controlled at 10oC to 70oC. Based on experimental data, a model is built for further verification by practical circuit application after the establishment of such module. The performance of this modulized model is found more accurate through comparison between simulation result and experimental data using a lighting circuit design composed of 5 pieces of 1 W-LED. This finding could provide a reference for future design aiming at high power LED driving circuit to reduce development and design cost.

碩士
國立虎尾科技大學
光電與材料科技研究所
101
In present, the thermoplastic polymer has been commonly utilized as one of LED packaging materials, in which thermoplastic-based PPA(Polyphthalamide) and PCT(Poly1,4-cyclohexylene dimethylene terephthalate)-based material are abundantly used. The PPA and PCT are mainly used for low- and medium-power applications, and both are the most commercial available materials in the LED packaging market. However, with reducing cost and increasing input power in LED solid-state lighting applications, the new packaging materials with better resistance to impact, humidity, heat, and encapsulant yellowing, have been developing for passing different environmental loads. Hence, there are some thermosetting polymer-based materials developed to meet the requirement, such as EMC (Epoxy Molding Compound) and SMC (Silicone Molding Compound), etc. The study is mainly focused on the applications of EMC package (with thermosetting polymer-based material) in high-power LED products, which is driven by greater than input power of 2W. First, it is to make a detailed analysis on each LED packaging process, such as sandblasting and punching, etc, and to further measure the initial light intensity of the package, relating to EMC''s reflectivity after packaged. Next, the material heat resistance and optical characterization for the package were examined before and after the long-term high-temperature aging and several reflow cycling tests. Finally, the adhesive bond at an interface between EMC material and silver leadframe was observed with a red ink experiments. In the mean time, the light decay and lifetime for the package were also determined by experimentally recording the LED light intensity when continually operated at a certain driven I=400mA under different ambient temperature conditions of 25 oC, 60 oC, 80 oC for a long time. Keywords: LED, Package, EMC thermosetting-based packaging material, PPA thermoplastic-based packaging material

The present work illustrates a detailed spectroscopic analysis carried out on dysprosium ions doped Zinc Alumino Sodium Phosphate (ZnAlNaP) glasses with a chemical composition of (10-x) ZnO 20Al2O3-10Na2O-60P2O5- xDy2O3 (x = 0.1 to 2.0 mol%). The XRD spectrum recorded for an un doped ZnAlNaP glass demonstrates a broad hump confirming its non-crystalline nature. The FT-IR and Raman spectrum recorded for an un-doped ZnAlNaP and ZnAlNaPDy1.0 glass elucidates various functional groups and vibrational modes involved. The DSC & TGA studies conducted on an un-doped ZnAlNaP glass revealed its overall weight loss and thermal stability. The absorption spectra recorded were used to calculate the optical bandgap for the titled glasses and were found to be in the range from 4.52 to 4.81 eV. To understand the applicability of the titled glasses for epoxy-free solid-state lighting devices, photoluminescence (excitation, emission, and decay) spectra were recorded and analysed. The photoluminescence (PL) emission recorded under 350 nm excitation show two significant bands, 4F9/2 6H15/2 (blue) and 4F9/2 6H13/2 (yellow) at 484 nm and 573 nm respectively. Temperature-dependent PL studies conducted on 1.0 mol% of the Dy3+ ions in ZnAlNaP glasses revealed activation energy of 0.212 eV with a percentage of loss 25.6% in PL intensity. The CIE-chromaticity coordinates and color correlated temperature (CCT) were evaluated from the PL spectral characteristics. All the spectroscopic investigations conducted on the titled glasses finally reveal their superior nature in fabricating epoxy-free white light-emitting diodes and other related optoelectronic devices.

博士
國立中興大學
材料科學與工程學系所
100
Gallium nitride (GaN) is a binary III/V direct bandgap semiconductor that has been widely used in light-emitting diodes (LEDs) since the 1990s. The compound is a hard material with a Wurtzite crystal structure. The wide band gap of 3.4 eV provides the material with special properties that facilitate its application in high-power and high-frequency devices. In this dissertation, GaN was grown on three different templates by metal organic chemical vapor deposition. The first two templates were selectively-etched GaN (SE-GaN, type I) and strip-patterned sapphire (SPS, type II) template, created with the aim of effectively reducing threading dislocation (TD) densities and increasing the internal quantum efficiency. The final template was a Ga2O3 template (type III), which could separate the sapphire substrate via a chemical etching process. We aim to enhance the effectiveness of this process as an alternative to laser lift-off technology, and to reduce the epitaxial cost. The type I SE-GaN templates were created using selective etching of GaN defects and the patterned sapphire substrate (PSS) technique. These templates acted as a TD growth mask in the GaN epitaxial layers, and achieved defect centralization. The etching pit density (EPD) of GaN grown on the SE-GaN template can reduce to 1.6 × 105 cm-2, and the output power of the SE-GaN LED sample under a 350 mA injection current can be enhanced by 46% as compared with that of the conventional GaN/sapphire LED one. The type II SPS templates were fabricated using photolithographic and wet-etching processes. The etching maximized the sapphire substrate area and graphics, which increased the light extraction efficiency and reduced TDs. The EPD of GaN grown on SPS templates can reduce to 5.3 × 106 cm-2. The output power of the SPS LED sample under a 350 mA injection current was enhanced by 40% as compared with that of the conventional GaN/sapphire LED one. The type III Ga2O3 templates, deposited using pulsed laser deposition on sapphire substrates, were used for the epitaxial growth of crystalline GaN on the Ga2O3 templates. An N2 ambient atmosphere was adopted because a severe degradation of the oxide material occurred under a H2 ambient atmosphere at high temperatures. Finally, the GaN LED structures were successfully grown on the.Ga2O3 template. A thin film LED was demonstrated, where the sacrificial Ga2O3 was easily achieved using a HF etchant; and the GaN and sapphire substrate can be successfully separated.

碩士
國立臺北科技大學
建築與都市設計研究所
102
Due to the limited angle of LED light-emission, light scattering from the LED light source and lamp combination can be poor, resulting in dark spots on the lamp shade. The objective of this study is to use lamp design and LED arrangement to achieve comprehensive light scattering. After review of the literature and case analysis, the author carried out the design based on IDEO design thinking. The focus of the design is on the LED light source characteristics and the degree of innovation of the lamps. Optical simulation software was applied for ray tracking, and one project was selected to be made into a physical model. Afterward, the investigator interviewed experts for suggestions on the light source and the style and appearance of the lamp. Suggestions from the experts were analyzed, integrated and adapted to correct shortcomings. Results from interviewing experts are summarized below. First, the lamp can create a comprehensive scattering effect that is similar to the light scattering of regular lamps. Secondly, with two light sources, top and bottom, and a dimmer controller, the lamp can be used to create spatial atmosphere, and the user can select iii the most comfortable light source. Third, color temperature change can be integrated into the light sources to create various types of atmosphere and styles. Fourth, according to consumer need, the lamp as designed has an adjustable pole that can accommodate rooms and space of different height. Lastly, there was a lack of experiments and tests during the design process. The investigator should also try to apply various types of light and materials because combining them can create many possibilities and opportunities.

Für die Druckproduktion ist eine Steuerung und daher eine akkurate Vorhersage des Reflexionsspektrums des Druckprodukts erforderlich, insbesondere, wenn hohe Anforderungen an die Qualität gestellt werden. Dieses Reflexionsspektrum hängt von verschiedenen Faktoren ab, darunter auch die Lichtstreueigenschaft des Bedruckstoffs, in den meisten Fällen Papier. Der Aufwand, ein typisches Druckermodell anzupassen, ist erheblich, denn Testfelder müssen gedruckt und gemessen werden. Mit einer steigenden Zahl von Druckfarben wird dies umso entscheidender, da die Anzahl der möglichen Kombinationen von übereinander gedruckten Farben exponentiell zunimmt. Sogenannte ”First Principle Models” reduzieren den Aufwand, indem die verschiedenen physikalischen Effekte separat modelliert werden. Ein typischer Ansatz ist hierbei die Trennung von optischer und mechanischer Tonwertzunahme. Für die Modellierung der optischen Tonwertzunahme ist die Messung der Lichtstreuung im Bedruckstoff eines der zentralen Elemente. Diese Arbeit stellt die nötigen Mittel bereit, um einen Messaufbau zu entwerfen, mit dem diese Lichtstreuung in Papier oder in anderen Bedruckstoffen erfasst werden kann. Ein solcher Messaufbau wurde realisiert und analysiert. Des Weiteren werden repräsentative Messergebnisse vorgestellt. Die wichtigsten Vorteile des ermittelten Messaufbaus sind die verbesserten Fokus-Werkzeuge, die Untersuchung über mögliche Ursachen von Messfehlern, und die winkelaufgelöste Messung um Anisotropie der Lichtstreuung feststellen zu können. In einer theoretischen Studie auf Basis von amplitudenmodulierten Druckrastern wird gezeigt, dass die optische Tonwertzunahme vorhergesagt werden kann, ohne dass Testfelder gedruckt werden müssen. Wenn die Lichtstreuung durch eine Punktstreufunktion beschrieben wird, ist dafür lediglich die Messung eines einzelnen Parameters nötig, wenn Transmission der Farbe und Rasterfrequenz bekannt sind. Eine Voraussetzung für diese Vorhersage der optischen Tonwertzunahme ist die akkurate und verlässliche Messung dieses Parameters. Der Messaufbau dieser Arbeit bietet die Möglichkeit hierzu. Daher ist diese Arbeit ein Beitrag für die Verbesserung von ”First Principle Models” durch die Entkopplung von optischer und mechanischer Tonwertzunahme.