Extending the pyramid WFS to LGSs: the INGOT WFS

Roberto Ragazzoni; Davide Greggio; Valentina Viotto; Simone Di Filippo; Marco Dima; Jacopo Farinato; Maria Bergomi; Elisa Portaluri; Demetrio Magrin; Luca Marafatto; Federico Biondi; Elena Carolo; Simonetta Chinellato; Gabriele Umbriaco; Daniele Vassallo

doi:10.1117/12.2313917

11 July 2018 Extending the pyramid WFS to LGSs: the INGOT WFS

Roberto Ragazzoni, Davide Greggio, Valentina Viotto, Simone Di Filippo, Marco Dima, Jacopo Farinato, Maria Bergomi, Elisa Portaluri, Demetrio Magrin, Luca Marafatto, Federico Biondi, Elena Carolo, Simonetta Chinellato, Gabriele Umbriaco, Daniele Vassallo

Author Affiliations +

Proceedings Volume 10703, Adaptive Optics Systems VI; 107033Y (2018) https://doi.org/10.1117/12.2313917
Event: SPIE Astronomical Telescopes + Instrumentation, 2018, Austin, Texas, United States

Abstract

Laser Guide Stars are, in spite of their name, all but “stars”. They do not stand at infinite distance, neither on a plane. If fired from the side of a large telescope their characteristics as seen from various points on the apertures changes dramatically. As they extend in a 3D world, there is need of a WFS that deploy in a similar 3D manner, in the conjugated volume, resembling the approach that MCAO required long time ago to overcome the usual limitations of conventional AO. We describe a class of a novel kind of WFS that employ a combination of refraction and reflection, such that they can convey the light from an LGS into a limited number of pupils, making the device compact, doable with a single piece of glass, and able to feed a minimum sized format detector where the information is collected maximizing the information depending from which part of the LGS the light is coming from, and on which portion of the telescope aperture the light is landing. They represent, in our opinion, the best-known adaptation of the pyramid WFS for NGS to the LGS world. As in the natural reference case the practical advantages come along with some fundamental advantages. Being a pupil plane WFS with the perturbator placed on the (3D) loci of focus of the various portions of the source of light they have the potentiality to extend WFS to a number of issues, including the ability to sense the islands effect, where non-contiguous portions of the main apertures are optically displaced. Further to their description and the main recipes we speculate onto possible variations on cases where the LGS is fired from the back of the secondary mirror and we exploit some potential features when implementing onto an extremely large aperture.

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Roberto Ragazzoni, Davide Greggio, Valentina Viotto, Simone Di Filippo, Marco Dima, Jacopo Farinato, Maria Bergomi, Elisa Portaluri, Demetrio Magrin, Luca Marafatto, Federico Biondi, Elena Carolo, Simonetta Chinellato, Gabriele Umbriaco, and Daniele Vassallo "Extending the pyramid WFS to LGSs: the INGOT WFS", Proc. SPIE 10703, Adaptive Optics Systems VI, 107033Y (11 July 2018); https://doi.org/10.1117/12.2313917

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