Det huvudsakliga syftet med denna uppsats är att undersöka vilken påverkan valet av ljusteknik, LED eller halogen har på den slutliga produkten. Studien kommer med hjälp av fokusgruppsintervjuer undersöka om personer kan se skillnad på en ljussättning som är gjord med LED- respektive halogenlampor samt vad de olika teknikerna ger för känsla. Vi jämför resultaten från fokusgruppsintervjuerna med tidigare litteratur som Set lighting technician's handbook: film lighting equipment, practice, and electrical distribution och Lighting for cinematography: a practical guide to the art and craft of lighting for the moving image. Fokusgruppsintervjuerna resulterade i något oväntade svar och gav oss en bredare och förtydligad förståelse för vad som spelar roll när det kommer till en publiks känslomässiga reaktion av en bild.

The Light-emitting diodes (LEDs) are rapidly emerging as the dominant light source given their high luminous efficacy, long lift span, and thanks to the newly enacted efficiency standards in favor of the more environmentally-friendly LED technology. The LED lighting market is expected to reach USD 105.66 billion by 2025. As such, the lighting industry requires LED drivers, which essentially are power converters, with high efficiency, wide input/output range, low cost, small form factor, and great performance in power factor, and luminance flicker. These requirements raise new challenges beyond the traditional power converter topologies. On the other hand, the development and improvement of new device technologies such as printed thin-film capacitors and integrated high voltage/power devices opens up many new opportunities for mitigating such challenges using innovative circuit design techniques and solutions. Almost all electric products needs certain power delivery, regulation or conversion circuits to meet the optimized operation conditions. Designing a high performance power converter is a real challenge given the market’s increasing requirements on energy efficiency, size, cost, form factor, EMI performance, human health impact, and so on. The design of a LED driver system covers from high voltage AC/DC and DC/DC power converters, to high frequency low voltage digital controllers, to power factor correction (PFC) and EMI filtering techniques, and to safety solutions such as galvanic isolation. In this thesis, we study design challenges and present corresponding solutions to realize highly integrated and high performance LED drivers combining switched-capacitor and resonant converters, applying re-configurable multi-level circuit topology, utilizing sigma delta modulation, and exploring capacitive galvanic isolation. A hybrid switched-capacitor-resonant (HSCR) LED driver based on a stackable switched-capacitor (SC) converter IC rated for 15 to 20 W applications. Bulky transformers have been replaced with a SC ladder to perform high-efficiency voltage step-down conversion; an L-C resonant output network provides almost lossless current regulation and demonstrates the potential of capacitive galvanic isolation. The integrated SC modules can be stacked in the voltage domain to handle a large range of input voltage ranges that largely exceed the voltage limitation of the medium-voltage-rated 120 V silicon technology. The LED driver demonstrates > 91% efficiency over a rectified input DC voltage range from 160 VDC to 180 VDC with two stacked ICs; using a stack of four ICs > 89.6% efficiency is demonstrated over an input range from 320 VDC to 360 VDC . The LED driver can dim its output power to around 10% of the rated power while maintaining >70% efficiency with a PWM controlled clock gating circuit. Next, the design of AC main rectifier and inverter front end with sigma delta modulation is described. The proposed circuits features a pair of sigma delta controlled multilevel converters. The first is a multilevel rectifier responsible for PFC and dimming. The second is a bidirectional multilevel inverter used to cancel AC power ripple from the DC bus. The system also contains an output stage that powers the LEDs with DC and provides for galvanic isolation. Its functional performance indicates that integrated multilevel converters are a viable topology for lighting and other similar applications.

For selected YAG:Ce sample the temperature dependent absorbtion and emission spectra were measured and used to simulate white LED behavior. Various CIE-xy dependencies were observed. Sample surface scaterring parameters were calibrated using a custom-made automated goniospektrometer, which provided measured data with fine accuracy. Finally, the measured data were used to construct a Geant4 simulation to optimize two light devices for output intensity and target CIE-xy coordinates. Powered by TCPDF (www.tcpdf.org)

Vitamin D is a fat-soluble hormone essential for humans as it is a key player in calcium and phosphorus homeostasis for bone mineralization, and is linked to many nonskeletal health outcomes such as autoimmune diseases and cardiovascular disease as well. The primary source of vitamin D is the conversion of 7-dehydrocholestrol (7-DHC), which naturally exists in the plasma membranes of skin cells, to previtamin D3 by the exposure to the ultraviolet-B (UV-B) portion of sunlight. Despite humans’ ability to cutaneously synthesize vitamin D, many factors limit this process, and consequently vitamin D deficiency has become a common medical issue worldwide. Deficient individuals may not respond well to traditional vitamin D replacement through dietary supplementation if suffering from fat malabsorption syndromes while unable to get sufficient vitamin D from sun exposure due to location, sunscreen use, or cultural practices, among other reasons. It has been previously reported that exposure to artificial sources of UV-B radiation (UV lamps, tanning beds, among others) produces cutaneous vitamin D, but heat generation, poor portability, and other inconveniences to the deficient patient limit therapeutic use of these devices. In addition, broad-spectrum sources of UV radiation reduce the production of vitamin D compared to narrow-band sources because of the photoequilibrium that is established. The advent of the light-emitting diode (LED) provided a compact, energy-efficient, high-intensity, low-heat alternative radiation source, and the recent development of the UV LED offers a viable alternative for developing a personalized vitamin D-producing device. This thesis presents evidence that UV LEDs have the capacity to efficiently synthesize vitamin D3 in vitro and in human skin. Ampoules of 7-DHC were irradiated in triplicate with LEDs at 280, 285, 290, 295, 298, 300, and 310 nm. The 298 nm LED was found to have the most efficient previtamin D3 production of 7.0% in vitro at the equivalent of 0.75 minimal erythemal dose (MED, rated at 1 MED = 32 milliJoules per centimeter squared for type II skin), compared to all other assessed LEDs. Irradiation of human skin samples (IRB-exempt) with the 298 nm diode (~39 seconds of radiation) indicated that 1.5% of the original 7-DHC in type II (Caucasian) skin could be converted to vitamin D3 in situ after exposure to 0.75 MED. These results imply that manufacturing a cuff containing 298 nm LEDs that covers 3.8% of the total surface area of skin could provide 600 IUs of vitamin D3 if operated for just 39.0 seconds. The data provide a promising new approach to treat vitamin D-deficient patients suffering from fat malabsorption syndromes.

This case study investigates how the biomass changes depending on changes made to the time interval for the lights and the distance between the crops and light. The study is split in three different cases and each case consists of three batches. The different baches have three different heights between the light and the crops and the heights being used is 55, 110 and 165cm. The light interval in the first case was 12 hours, 6 hours for case 2 and 3 hours for the last case.  Case 1 had an average biomass weight of 28,5 g, for batches 1-3 and the light interval was twelve hours. In case 1 and 2 the pea plants looked healthy and green but in case 2 the plants were taller, and the leaves had widened more. Case 2 had an average biomass weight of     55,5 g, for batches 4-6 when the interval of the lights was 6 hours. The last case generated the most biomass of all the cases with an average of 102,5 g for batches 7-9, and the plants was completely yellow. Case 2 compared to case 1 gave double biomass yield for the same amount of energy used. One-way Anova determined that it was not any statistically significant difference between the batches but, however, it was for the different cases.

In der vorliegenden Arbeit wurden Lanthanoidmolybdate der allgemeinen Zusammensetzung Ln2MoO6, Ln2Mo2O9, Ln2Mo3O12, MLnMo2O8 (Ln= La, Pr-Lu und Y; M = Li-Cs) bezüglich ihrer kristallographischen sowie spektroskopischen Eigenschaften untersucht. Die Darstellung dieser Verbindungen erfolgte über Festkörperreaktionen bei Temperaturen zwischen 800 und 1000°C. In den Molybdat-Wirtsgittern mit Ln = La bzw. Ln = Gd wurden Lanthan bzw. Gadolinium in Abstufungen von 10, 30, 50, 75 und 100% durch trivalentes Europium substituiert und daraufhin mittels Lumineszenzspektroskopie eine Anwendung in pcLEDs evaluiert. Als herausragend erwies sich das System LiLnMo2O8 (Ln = La, Pr-Lu und Y). In diesem tetragonalen Wirtsgitter lassen sich alle Lanthanoidionen unabhängig vom Ionenradius miteinander kombinieren, ohne dass es zu einer Phasenumwandlung kommt. Somit kann eine Vielzahl von interessanten optischen Materialien entwickelt werden. Als geeigneter LED-Leuchtstoff wurde LiLa1-xEuxMo2O8 hergestellt und auf seine optischen Eigenschaften hin untersucht. Dieses Wirtsgitter zeigt auch bei einer vollständigen Substitution von Lanthan durch Europium keine Löschung der Lumineszenz. Durch Optimierung der Synthesebedingungen konnte mit LiEuMo2O8 bei Anregung mit 465 nm reproduzierbar eine Quantenausbeute von 100% erreicht werden. Das Lumenäquivalent ist mit 280 lm/W für eine Leuchtstoffanwendung ausreichend hoch.

A lack of efficient red luminecscent line emitters which exhibit a high absorption between 400 and 500 nm of the electromagnetical spectrum was the decisive factor to start this work. The invention of the blue LED (light emitting diode) enables the production of white light by combining the blue emitting LED with a yellow emitting phosphor. Advances in chip technology lead to high power LEDs with a power consumption of several watts. Long lifetimes (>50 000 working hours) and their high energy efficiency make them very interesting for the lighting market, but further problems have to be solved for the application in general lighting. A big issue for warm-white LEDs are colour rendering and colour temperature due to the lack of red parts in the spectrum. Another important feature of light sources is a stable colour over time. Therefore the applied converter material has to be chemically and photochemically stable. The chip-phosphor package is operated at working temperatures of about 150 to 200¡C Ð that also should not influence performance of the phosphor material. High absorption at the emission maximum of the LED and a high conversion efficiency (>90%) are important properties for designing a marketable converter material. In this work tungstates were studied due to their high chemical stability and their high alkaline character. Their use as a host lattice for lanthanide ions was investigated. LiLaW2O8 with 50 mol-% and La2W3O12 with 40 mol-% EuIII show the best performance in converting the blue light of the chip with quantum efficiencies of up to 90% at high absorption cross-setctions. Further investigations of temperature behaviour, long term durability under high photon fluxes and their conversion efficiency of the blue emitted to red converted light have to be done to allow a statement about their use in LED applications.

With experimental realization of micro-structures, the feasibility of achieving high brightness, low efficiency droop blue LED was implemented based on InGaN/GaN micro-LED-pillar design. A significantly high current density of 492 A/cm2 in a 20 μm diameter (D) micro-LED-pillar was achieved, compared to that of a 200 μm diameter LED (20 A/cm2), both at 10 V bias voltage. In addition, an increase in sustained quantum efficiency from 70.2% to 83.7% at high injection current density (200 A/cm2) was observed in micro-LED-pillars in conjunction with size reduction from 80 μm to 20 μm. A correlation between the strain relief and the electrical performance improvement was established for micro-LED-pillars with D < 50 μm, apart from current spreading effect. The degree of strain relief and its distribution were further studied in micro-LED-pillars with D ranging from 1 μm to 15 μm. Significant wavenumbers down-shifts for E2 and A1 Raman peaks, together with the blue shifted PL peak emission, were observed in as-prepared pillars, reflecting the degree of strain relief. A sharp transition from strained to relaxed epitaxy region was discernible from the competing E2 phonon peaks at 572 cm-1 and 568 cm-1, which were attributed to strain residue and strain relief, respectively. A uniform strain relief at the center of micro-pillars was achieved, i.e. merging of the competing phonon peaks, after Rapid Thermal Annealing (RTA) at 950℃ for 20 seconds, phenomenon of which was observed for the first time. The transition from maximum strain relief to a uniform strain relief was found along the narrow circumference (< 2.5 μm) of the pillars from the line-map of Raman spectroscopy. The extent of strain relief is also examined considering the height (L) of micro-LED-pillars fabricated using FIB micro-machining technique. The significant strain relief of up to 70% (from -1.4 GPa to -0.37 GPa), with a 71 meV PL peak blue shift, suggested that micro-LED-pillar with D < 3 μm and L > 3 μm in the array configuration would allow the building of practical devices. Overall, this work demonstrated a novel top-down approach to manufacture large effective-area, high brightness emitters for solid-state lighting applications.

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Depuis le début des années 2000, les performances des LED ne cessent de s'améliorer et permettent l'ancrage de cette technologie dans de nombreux domaines d'applications. Stimulées par le marché de l'éclairage, les LED présentent une longue durée de vie et une grande robustesse pour un prix par watt optique défiant toute concurrence. Pour améliorer leur luminance, les LED peuvent être couplées à des concentrateurs luminescents.La première partie de cette thèse expose la mise au point des premiers concentrateurs luminescents dans SWIR (gamme 1,2-2,5 µm où les LED sont peu efficaces). Nous montrons que la luminance des concentrateurs luminescents dans le SWIR dépasse celle des LED d'un ordre de grandeur. Elle rend possible la détection de l'eau dans l'industrie agroalimentaire ainsi que l'inspection de wafers de silicium. Dans le visible, les performances des concentrateurs luminescents (luminance, spectre, prix, régime de fonctionnement) offrent une combinaison unique des avantages des lampes flash et des diodes laser. La seconde partie de cette thèse explore la possibilité d'utiliser ces concentrateurs luminescents pour pomper des lasers solides. Cette étude démontre la compatibilité de ce nouveau type de pompage avec les cristaux dopés aux métaux de transition, incontournables dans le domaine des lasers ultra-courts. Pour la première fois, un effet laser en régime relaxé est obtenu via le pompage par LED du Cr:LiSGaF, du Cr:LiSAF, de l’alexandrite, et du Ti:saphir. Ces premières démonstrations ouvrent la voie à des systèmes laser basés sur le pompage par LED. Plusieurs systèmes sont mis en place tels que des oscillateurs lasers en régime déclenché (Q-switch et cavity-dump) faisant l'objet de conversions de fréquence, et des amplificateurs d'impulsions laser. / Since the beginning of the 2000s, LED's performance have known dramatic improvements which enable this technology to settle down in numerous application areas. Driven by the lighting market, LED are characterized by their long lifetime, their ruggedness, and their low cost per emitted optical watt. In order to go beyond LED's brightness, they can be coupled to luminescent concentrators.The first part of this work exposes the development of the first luminescent concentrator in the short-wave infrared (or SWIR corresponding to the 1.2-2.5 µm band where LED have very low powers). This work shows that the brightness of the luminescent concentrators in the SWIR exceeds by one order of magnitude LED's brightness in the same spectral range. This light source allows water detection for the agrifood industry and the inspection of silicon wafers for microelectronics. In the visible, the performance of luminescent concentrators (brightness, spectrum, price, mode of operation) offer a unique trade-off between flashlamps and laser diodes. The second part of this work investigates the use luminescent concentrators emitting in the visible to pump solid-state lasers. The compatibility of this new pumping concept is attested with transition-metals-doped crystals, cornerstone of ultrafast laser sources. For the first time, laser oscillations in free-running operation are obtained by LED-pumping of Cr:LiSGAF, Cr:LiSAF, alexandrite and Ti:sapphire. These early results open the way to LED-pumped laser systems. Several systems are implemented such as laser oscillators in pulsed operation (Q-switch and cavity dump) followed by frequency conversions and laser pulses amplifiers.