Step-selective measurement by grating-based lateral shearing interferometry for segmented telescopes |
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Authors: | Bruno Toulon Jérôme Primot Sabrina Velghe |
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Institution: | a Office National d’Etudes et de Recherches Aérospatiales, Chemin de la Hunière, F-91761 Palaiseau Cedex, France b Phasics SA, XTEC, Campus de l’Ecole Polytechnique, F-91128 Palaiseau, France c Laboratoire Charles Fabry de l’Institut d’Optique, Campus Polytechnique, RD 128, F-91127 Palaiseau Cedex, France |
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Abstract: | We present an original step-selective mode which allows to measure only the steps and not the slowly varying aberrations of a wave front. This mode can be implemented when measuring segmented wave front by a diffraction-grating-based lateral shearing interferometer. This set-up rests on the different chromatic response of these interferometers depending on the rate of change of the impinging wave front: for smooth defects, the response is classically achromatic whereas it is chromatic for a step variation, which was to our knowledge overlooked. The interest of this mode for astronomical measurements is highlighted. First we present theoretical considerations to show how this mode of measure is possible; then a numerical simulation illustrates them. |
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Keywords: | 42 25 Hz 42 62 Eh 42 79 Dj 42 68 Wt |
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