The Ingot wavefront sensor is a novel pupil-plane wavefront sensor, specifically designed to cope with the elongation typical of the extended nature of the Laser Guide Star (LGS). In the framework of the ELT, we propose an optical solution suitable for a Laser launch telescope, located outside the telescope pupil. In this paper, we present the current optical design, based on a reflective roof-shaped prism, which, at the level of the focal plane, splits the light from an LGS producing three beams. The three images of the telescope pupils can be then used for the retrieval of the first derivative of the wavefront. The 3D nature of such a device requires new alignment techniques to be determined theoretically and verified in the real world. A possible fully automated procedure, relying solely on the illumination observed at the three pupils, to align the prism to the image of the LGS is discussed. Careful attention needs to be put both on the telecentricity of the system and on the reference systems of the Ingot adjustments in the 3D space. This is crucial in order to disentangle all the possible misalignment effects. In this context, we devised a test-bench able to reproduce, in a scaled manner, the 3D illumination that the Ingot will face at the ELT, in order to validate the design and to perform preliminary tests of phase retrieval.
@article{arxiv.2101.07742,
title = {INGOT Wavefront Sensor: from the optical design to a preliminary laboratory test},
author = {Simone Di Filippo and Davide Greggio and Maria Bergomi and Kalyan Radhakrishnan and Elisa Portaluri and Valentina Viotto and Carmelo Arcidiacono and Demetrio Magrin and Luca Marafatto and Marco Dima and Roberto Ragazzoni and Pierre Janin-Potiron and Lauren Schatz and Benoit Neichel and Olivier Fauvarque and Thierry Fusco},
journal= {arXiv preprint arXiv:2101.07742},
year = {2021}
}