O objetivo deste trabalho é apresentar um estudo comparativo entre as principais tecnologias utilizadas como fonte de luz para faróis automotivos. Inicialmente, esta dissertação apresenta uma breve introdução sobre a história dos faróis automotivos, desde os primeiros modelos até os protótipos em desenvolvimento que utilizam diodos emissores de luz (LEDs). Estes últimos surgem como uma possível alternativa às tradicionais lâmpadas incandescentes ou àquelas que funcionam por de descarga de gás. A tecnologia dos faróis a LED é baseada nos semicondutores emissores de luz branca de alto desempenho. Porém, apenas recentemente, esta tecnologia apresentou os primeiros sinais de viabilidade para aplicações automotivas devido ao crescente incremento na intensidade da luz emitida por estes semicondutores. Para desenvolver o estudo comparativo proposto, foram selecionados três faróis, sendo dois deles representantes das tecnologias atuais e o outro um farol a LED. Foram também estabelecidos critérios para comparação entre os seus desempenhos e realizados ensaios experimentais. Por fim, este trabalho fornece, sinteticamente, os principais resultados dos ensaios, enumerando as vantagens e desvantagens dos faróis com LEDs frente aos convencionais, além das barreiras existentes para aplicação desta nova tecnologia. / This work aims to present a comparative study among main technologies used as light sources for automotive headlamps. Initially, this thesis presents a brief introduction on the history of automotive headlamps, since the first models until the prototypes under development employing Light Emitting Diodes (LEDs). These last ones appear as a possible alternative to either traditional incandescent light or even to gas discharge bulbs. The technology of the LED-headlamps is based on high performance white light emitting semiconductors. In fact, recently this technology presented the first signals of feasibility for automotive applications due to the growing increment in the intensity of the light emitted by these semiconductors. To develop the proposed comparative study, three headlamps were selected, being two of them representatives of the current technologies and the other one is a LEDheadlamp. Some criteria for comparison among their performances had been established and experimental tests were also performed. Finally, this work supplies, synthetically, the main results of the tests, enumerating the advantages and disadvantages of LED-headlamps in comparison with conventional ones. In addition to, it comments the existing barriers for application of this new technology as well.

O objetivo deste trabalho é apresentar um estudo comparativo entre as principais tecnologias utilizadas como fonte de luz para faróis automotivos. Inicialmente, esta dissertação apresenta uma breve introdução sobre a história dos faróis automotivos, desde os primeiros modelos até os protótipos em desenvolvimento que utilizam diodos emissores de luz (LEDs). Estes últimos surgem como uma possível alternativa às tradicionais lâmpadas incandescentes ou àquelas que funcionam por de descarga de gás. A tecnologia dos faróis a LED é baseada nos semicondutores emissores de luz branca de alto desempenho. Porém, apenas recentemente, esta tecnologia apresentou os primeiros sinais de viabilidade para aplicações automotivas devido ao crescente incremento na intensidade da luz emitida por estes semicondutores. Para desenvolver o estudo comparativo proposto, foram selecionados três faróis, sendo dois deles representantes das tecnologias atuais e o outro um farol a LED. Foram também estabelecidos critérios para comparação entre os seus desempenhos e realizados ensaios experimentais. Por fim, este trabalho fornece, sinteticamente, os principais resultados dos ensaios, enumerando as vantagens e desvantagens dos faróis com LEDs frente aos convencionais, além das barreiras existentes para aplicação desta nova tecnologia. / This work aims to present a comparative study among main technologies used as light sources for automotive headlamps. Initially, this thesis presents a brief introduction on the history of automotive headlamps, since the first models until the prototypes under development employing Light Emitting Diodes (LEDs). These last ones appear as a possible alternative to either traditional incandescent light or even to gas discharge bulbs. The technology of the LED-headlamps is based on high performance white light emitting semiconductors. In fact, recently this technology presented the first signals of feasibility for automotive applications due to the growing increment in the intensity of the light emitted by these semiconductors. To develop the proposed comparative study, three headlamps were selected, being two of them representatives of the current technologies and the other one is a LEDheadlamp. Some criteria for comparison among their performances had been established and experimental tests were also performed. Finally, this work supplies, synthetically, the main results of the tests, enumerating the advantages and disadvantages of LED-headlamps in comparison with conventional ones. In addition to, it comments the existing barriers for application of this new technology as well.

This thesis considers the problem of calculating and observing the mixing of modes of positive and negative frequency in inhomogeneous, dispersive media. Scattering of vacuum modes of the electromagnetic field at a moving interface in the refractive index of a dielectric medium is discussed. Kinematics arguments are used to demonstrate that this interface may, in a regime of linear dispersion, act as the analogue of the event horizon of a black hole to modes of the field. Furthermore, a study of the dispersion of the dielectric shows that five distinct configurations of modes of the inhomogeneous medium at the interface exist as a function of frequency. Thus it is shown that the interface is simultaneously a black- and white-hole horizon-like and horizonless emitter. The role, and importance, of negative-frequency modes of the field in mode conversion at the horizon is established and yields a calculation of the spontaneous photonic flux at the interface. An algorithm to calculate the scattering of vacuum modes at the interface is introduced. Spectra of the photonic flux in the moving and laboratory frame, for all modes and all realisable increase in the refractive index at the interface are computed. As a result of the various mode configurations, the spectra are highly structured in intervals with black-hole, white-hole and no horizon. The spectra are dominated by a negative-frequency mode, which is the partner in any Hawking-type emission. An experiment in which an incoming positive-frequency wave is populated with photons is assembled to observe the transfer of energy to outgoing waves of positive and negative frequency at the horizon. The effect of mode conversion at the interface is clearly shown to be a feature of horizon physics. This is a classical version of the quantum experiment that aims at validating the mechanism of Hawking radiation.