De nombreux efforts fournis sur l’avancement de la technologie de dépôt afin de répondre au besoin des utilisateurs des filtres interférentiels ont donné la naissance à la nouvelle génération des composants optiques. Les progrès techniques permettent de fabriquer les filtres avec la structure particulièrement complexe et atteindre les performances spectrales remarquables, mais aussi soulèvent de nouveaux problèmes au niveau de la diffusion. Les indicatrices de diffusion de ces filtres présentent les variations extrêmement rapides en fonction de l’angle de reprise et de la longueur d’onde, ce qui amoindrit sérieusement les performances des composants. Il est donc d’essentiel d’être capable de caractériser la diffusion lumineuse angulairement et spectralement résolue. L’objectif de cette thèse a alors été de développer l’outil expérimental, déduit pour la métrologie fine de la réponse spectrale et de la diffusion lumineuse. Le travail réalisé a donné naissance au banc SALSA (pour Spectral and Angular Light Scattering characterization Apparatus), un nouveau diffusomètre spectralement et angulairement résolu. Grâce au banc SALSA nous pouvons effectuer les mesures de diffusion sur large gamme spectrale [400 nm -1000 nm] avec la dynamique de 8 décades et la précision meilleure que 1%. Par ailleurs, le banc peut être utilisé pour la mesure de la transmission avec la dynamique de 12 décades, ce qui est performance unique sur l’échèle mondiale. / Due to market demand and technical progresses, a new generation of optical components requires much more sophisticated structures with a great number of layers. These complex structures enable to achieve severe optical performances but, at the same time, enhance light scattering processes. For these reasons, it is essential to develop a metrological tool which provides an accurate quantification of the spectral and angular behavior of scattering losses, with sufficient angular and spectral resolution. In order to face this issue, new investigations were performed during this PhD thesis and led to the development of the new scatterometer SALSA (Spectral and Angular Light Scattering characterization Apparatus). The use of both a broad-band source and a tunable filter allows to accurately select the illumination wavelength and the spectral bandwidth on the whole spectral range of CCD detectivity. Set-up SALSA allows us to perform the measurements of scattering losses on a wide spectral range (400-1000 nm), with high dynamics (>8 decades), high accuracy and low detectivity (a few 10-8 sr-1). Moreover, with set-up SALSA we are able to measure the transmission of interferential filters on the same spectral range, with high accuracy (1%) and a high dynamic (>10 decades, which is a unique performance).

The eyes of snakes and most geckos, as well as a number of other disparate squamate taxa, are shielded beneath a layer of transparent integument referred to as the “reptilian spectacle.” Derived from the embryonic fusion of palpebral tissues, the spectacle contains a number of specializations of the skin to benefit vision while still allowing it to function as the primary barrier to the environment. For example, in nearly all species that possess it, it is markedly thinned compared to the surrounding integument and its keratinized scale is optically transparent. While the spectacle may thus seem ideally adapted to vision in allowing the eyes to be always unoccluded, it does have a few drawbacks. One such drawback is its vascularity, the implications of which are still not fully understood, but are explored herein. As no recent synthesis exists of the body of knowledge on reptilian spectacles, the first chapter of this thesis consists of a review of spectacle anatomy, physiology, adaptive significance and evolution to help put into context the following chapters that present original research. The second chapter describes the dynamics of blood flow through the spectacle vasculature of colubrid snakes, demonstrating three main points: (1) that the spectacle vasculature exhibits cycles of regular dilation and constriction, (2) that the visual perception of a threat induces vasoconstriction of its vessels, and (3) that spectacle vessels remain dilated throughout the renewal phase. The implications of these points are discussed. The third chapter describes the spectral transmittance of the shed spectacle scale, the only keratinized structure in the animal kingdom to contribute to the dioptric apparatus of the eye, as well as its thickness. Spectacle scale transmittance and thickness was found to differ dramatically between snakes and geckos and found in snakes to vary between families. The adaptive significance of the observed variation is discussed. The fourth chapter describes biochemical analyses of the shed spectacle scales of snakes and geckos and compares their composition to other scales in the integument. Spectacle scales were found to differ significantly from other scales in their keratin composition, and gecko spectacle scales in particular were found to lack ß keratin, that hard corneous protein thought to be common to all reptile scales. The concluding chapter will discuss where this research has brought the state of our knowledge on the spectacle and offers thoughts on potentially useful avenues for further research.

The eyes of snakes and most geckos, as well as a number of other disparate squamate taxa, are shielded beneath a layer of transparent integument referred to as the “reptilian spectacle.” Derived from the embryonic fusion of palpebral tissues, the spectacle contains a number of specializations of the skin to benefit vision while still allowing it to function as the primary barrier to the environment. For example, in nearly all species that possess it, it is markedly thinned compared to the surrounding integument and its keratinized scale is optically transparent. While the spectacle may thus seem ideally adapted to vision in allowing the eyes to be always unoccluded, it does have a few drawbacks. One such drawback is its vascularity, the implications of which are still not fully understood, but are explored herein. As no recent synthesis exists of the body of knowledge on reptilian spectacles, the first chapter of this thesis consists of a review of spectacle anatomy, physiology, adaptive significance and evolution to help put into context the following chapters that present original research. The second chapter describes the dynamics of blood flow through the spectacle vasculature of colubrid snakes, demonstrating three main points: (1) that the spectacle vasculature exhibits cycles of regular dilation and constriction, (2) that the visual perception of a threat induces vasoconstriction of its vessels, and (3) that spectacle vessels remain dilated throughout the renewal phase. The implications of these points are discussed. The third chapter describes the spectral transmittance of the shed spectacle scale, the only keratinized structure in the animal kingdom to contribute to the dioptric apparatus of the eye, as well as its thickness. Spectacle scale transmittance and thickness was found to differ dramatically between snakes and geckos and found in snakes to vary between families. The adaptive significance of the observed variation is discussed. The fourth chapter describes biochemical analyses of the shed spectacle scales of snakes and geckos and compares their composition to other scales in the integument. Spectacle scales were found to differ significantly from other scales in their keratin composition, and gecko spectacle scales in particular were found to lack ß keratin, that hard corneous protein thought to be common to all reptile scales. The concluding chapter will discuss where this research has brought the state of our knowledge on the spectacle and offers thoughts on potentially useful avenues for further research.