Active Optics II. Results of an Experiment with a Thin 1 m Test Mirror

Noethe, L.; Franza, F.; Giordano, P.; Wilson, Raymond N.; Citterio, O.; Conti, Gualtiero Nunzi; Mattaini, E.

doi:10.1080/09500348814551591

Cited by 45 publications

(12 citation statements)

References 3 publications

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“…The segmented active optics first developed in Keck telescope 15 is a great progress in astronomical telescope, which open a new way to build very large, even extremely large telescopes. Also the thin deformable mirror active optics developed in Europe for NTT, VLT [16][17][18][19] , break through bottleneck of 5 to 6 meters aperture of the large telescope, and started to build very large monolithic mirror telescope with a best image quality. Based on their pioneering work, and some study and experiments in China 20-23 , we developed the third type of active optics-an active optics combine both segmented and thin deformable active optics, make this important telescope technology progress and stepped forward.…”

Section: Test Results By Guiding Camerasmentioning

confidence: 99%

The optical performance of LAMOST telescope

Cui¹,

Su²,

Wang³

et al. 2010

SPIE Proceedings

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The Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) project has completed its engineering work, and is going to finish commissioning around the end of 2010. The LAMOST telescope is with both large aperture and wide field of view to achieve the large scale spectroscopic survey observation. It is an innovative large aperture meridian active reflecting Schmidt configuration achieved by an active deformable Schmidt mirror, which could not be realized by the traditional optical system. Its primary mirror and active Schmidt mirror are both segmented, and composed of 37 and 24 hexagonal sub-mirrors respectively. A new active optics method succesfully developed in the active deformable Schmidt mirror of LAMOST. It is a conbination of the thin deformable mirror active optics and segmented active optics. This paper presents the optical performance of the telescope of LAMOST during optical test. It is shown that LAMOST project successfully resolving the big technical challenges, and making the progress in active optics and telescope technology.

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Section: Test Results By Guiding Camerasmentioning

confidence: 99%

The optical performance of LAMOST telescope

Cui¹,

Su²,

Wang³

et al. 2010

SPIE Proceedings

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“…To solve matching issues in concentrators we thought to reinterpret optical concepts largely used in astronomy, where an accurate image formation is an essential premise for efficient observations. In telescopes, controlled mirrors deformations are introduced by actuators to balance the optical aberrations that degrade the wavefront coming from an observed source [34][35][36]. What we developed instead is a sort of ''reverse'' approach of the astrophysical method: the guideline is to apply deformations (active or static) to the mirrors of the solar collectors to introduce aberrations in the wavefront, thus degrading the solar image and, in the case of a CPV dense array system, focusing a squared spot with a prescribed irradiance.…”

Section: Optical Conceptmentioning

confidence: 99%

Enhancing the efficiency of solar concentrators by controlled optical aberrations: Method and photovoltaic application

et al. 2015

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“…Active Optics allows controlling the deformations of optical components to obtain complex surfaces of high optical quality, statically or dynamically. Based on the elasticity theory, the parametrization of mirror's deformation allows their control in situ or during their manufacturing, resulting in the following main applications (Lemaitre 2009): 1. large amplitude aspherization of optics by stress polishing and/or by in situ stressing (Everhart 1966;Nelson et al 1980;Sporer 2006;Lemaitre 2005); 2. in situ compensation of large telescope mirrors owing to their deflection in field gravity (Noethe et al 1988;Wilson 1999); 3. availability of a variable asphericity for telescopes with multiple focii selected by mirror interchanging (Lemaitre et al , 1989); 4. field compensation and cophasing of optical telescope arrays by variable curvature/astigmatism mirrors, (Ferrari 1998;Hugot et al 2008); 5. segments and diffraction gratings aspherized by replication techniques from active submasters (Huber et al 1981).…”

Section: Active Optics and Stress Polishingmentioning

confidence: 99%

Stress polishing of thin shells for adaptive secondary mirrors

Hugot

Ferrari

Riccardi

et al. 2011

A&A

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Context. Adaptive secondary mirrors (ASM) are, or will be, key components on all modern telescopes, providing improved seeing conditions or diffraction limited images, thanks to the high-order atmospheric turbulence correction obtained by controlling the shape of a thin mirror. Their development is a key milestone towards future extremely large telescopes (ELT) where this technology is mandatory for successful observations. Aims. The key point of actual adaptive secondaries technology is the thin glass mirror that acts as a deformable membrane, often aspheric. On 6 m−8 m class telescopes, these are typically 1 m-class with a 2 mm thickness. The optical quality of this shell must be sufficiently good not to degrade the correction, meaning that high spatial frequency errors must be avoided. The innovative method presented here aims at generating aspherical shapes by elastic bending to reach high optical qualities. Methods. This method is called stress polishing and allows generating aspherical optics of a large amplitude with a simple spherical polishing with a full sized lap applied on a warped blank. The main advantage of this technique is the smooth optical quality obtained, free of high spatial frequency ripples as they are classically caused by subaperture toolmarks. After describing the manufacturing process we developed, our analytical calculations lead to a preliminary definition of the geometry of the blank, which allows a precise bending of the substrate. The finite element analysis (FEA) can be performed to refine this geometry by using an iterative method with a criterion based on the power spectral density of the displacement map of the optical surface. Results. Considering the specific case of the Very Large Telescope (VLT) deformable secondary mirror (DSM), extensive FEA were performed for the optimisation of the geometry. Results are showing that the warping will not introduce surface errors higher than 0.3 nm rms on the minimal spatial scale considered on the mirror. Simulations of the flattening operation of the shell also demonstrate that the actuators system is able to correct manufacturing surface errors coming from the warping of the blank with a residual error lower than 8 nm rms.

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Active Optics II. Results of an Experiment with a Thin 1 m Test Mirror

Cited by 45 publications

References 3 publications

The optical performance of LAMOST telescope

The optical performance of LAMOST telescope

Enhancing the efficiency of solar concentrators by controlled optical aberrations: Method and photovoltaic application

Stress polishing of thin shells for adaptive secondary mirrors

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