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Caractérisations quantitatives 3D à l'échelle nanométrique de l'extrême surface de lentilles à dioptres asphériques par analyse d'images.

Abstract : The purpose of this work between Thalès-Angénieux and the l'Ecole Nationale Supérieure des Mines of Saint-Étienne as part of a CIFRE contract, is about the analysis and the characterization of defects appearing during various stages of the manufacturing processes of aspheric surfaces especially in calcium fluoride. The realized lenses must be integrated into products and they mustn't present critical defects. Calcium fluoride is often used in precision optics especially for the transmission characteristics. The realization of aspheric lenses is also complex. The manufacturing processes of these surfaces can be done by several methods. Traditional methods of polishing or based on microgrinding and diamond turning are usually used. The last one, relatively easier, faster and cheaper, gives nevertheless unacceptable surfaces results, not in term of form and roughness but several pulling out areas appeared on the diopters. Means of profilometry measurement, deflectometry, interferometry under visible monochromatic and polychromatic wavelengths generally used at each stage of these processes become insufficient and do not allow us anymore to explain the origin of the pulling out zones. A study of the crystallographic structure by X-rays scattering as well as an interpretation of the results by a software of image analysis make it possible to explain this phenomenon and to connect the orientation of the single crystal of calcium fluoride with the realization of dioptres without any defects. Therefore it becomes possible to return to the machining conditions and to modify them in order to obtain surfaces devoid from defects.
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Submitted on : Tuesday, March 12, 2013 - 4:17:44 PM
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  • HAL Id : tel-00799798, version 1

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Sylvain Gras. Caractérisations quantitatives 3D à l'échelle nanométrique de l'extrême surface de lentilles à dioptres asphériques par analyse d'images.. Traitement du signal et de l'image [eess.SP]. Ecole Nationale Supérieure des Mines de Saint-Etienne, 2007. Français. ⟨NNT : 440 IVS⟩. ⟨tel-00799798⟩

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