5 June 2018 Optical design of the post focal relay of MAORY
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Abstract
The Multi Conjugate Adaptive Optics RelaY (MAORY) is foreseen to be installed at the straight through focus over the Nasmyth platform of the future Extremely Large Telescope (ELT). MAORY has to re-image the telescope focal plane with diffraction limited quality and low geometric distortion, over a field of view of 20 arcsec diameter, for a wavelength range between 0.8 μm and 2.4 μm. Good and uniform Strehl ratio, accomplished with high sky coverage, is required for the wide field science. Two exit ports will be fed by MAORY. The first one is for a wide field Camera that is supposed to be placed on a gravity invariant port with an unvignetted FoV of 53 arcsec x 53 arcsec where diffraction limited optical quality (< 54nm RMS of wavefront error at the wavelength of 1 μm) and very low field distortion (< 0.1% RMS) must be delivered. The requirements regarding the optical quality, distortion and optical interfaces, together with the desire of reducing the number of reflecting surfaces (and consequently the thermal background), optics wavefront error (WFE), overall size, weight and possibly cost, drove the design to have 2 Deformable Mirrors (DMs) with optical power. The Post Focal Relay (PFR) is also required to split the 589 nm wavelength light of the Laser Guide Stars (LGS), used for high order wavefront sensing, by means of a dichroic that lets the light of 6 LGSs, arranged on a circle of about 90 arcsec diameter, pass through and reflects science beam. Behind the dichroic an objective creates the LGS image plane for the WFSs channel. We present in this paper the optical design and the tolerance analysis of the PFR and the objective. The tolerance analysis concerning the manufacturing and the alignment precision is also shown.
© (2018) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
M. Lombini, D. Magrin, M. Patti, D. Greggio, F. Cortecchia, E. Diolaiti, V. De Caprio, A. De Rosa, E. Radaelli, M. Riva, P. Ciliegi, S. Esposito, P. Feautrier, R. Ragazzoni, "Optical design of the post focal relay of MAORY", Proc. SPIE 10690, Optical Design and Engineering VII, 1069011 (5 June 2018); doi: 10.1117/12.2312010; https://doi.org/10.1117/12.2312010
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