Deformable secondary mirrors for the LBT adaptive optics system

Martin, Hubert M.; Zappellini, Guido Brusa; Cuerden, Brian; Miller, Stephen Matteo; Riccardi, Armando; Smith, Blaine E.

doi:10.1117/12.672698

Cited by 23 publications

(17 citation statements)

References 10 publications

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“…The aspheric shell manufacturing is a delicate process (see Ref. [4] for LBT) because of the low thickness, but, in principle, the optical specifications for it can be relaxed, considering that actuators can compensate for figuring errors. However the amount of this static error is limited by three main factors:…”

Section: Introductionmentioning

confidence: 99%

Optical figuring specifications for thin shells to be used in adaptive telescope mirrors

Riccardi

2006

SPIE Proceedings

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Section: Introductionmentioning

confidence: 99%

Optical figuring specifications for thin shells to be used in adaptive telescope mirrors

Riccardi

2006

SPIE Proceedings

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“…Detailed descriptions of the LBT-AdOpt system and follow-ups of its development have been presented many times [1][2][3][4] and are updated in this same conference 5, 6 . The system is essentially subdivided into two largely independent subsystems: a pyramid based Wavefront Sensor 2, 3 (WFS), and an Adaptive Secondary mirror [7][8][9][10][11] (AdSec).…”

Section: The Lbt-adopt Systemmentioning

confidence: 99%

The LBT-AdOpt arbitrator: coordinating many loosely coupled processes

Fini

Tosetti

Busoni

et al. 2008

Advanced Software and Control for Astronomy II

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The LBT-AdOpt Supervisor is a collection of software processes which control the operations on the set of devices which make up the Adaptive Optics subsystem. The Arbitrator is the software component which coordinates the operations of the Supervisor in order to support operations at the telescope in reply to requests issued by the Instrument Control Software.In this paper we describe the architecture of the Arbitrator, based on an extremely modular, extensible and maintainable approach, designed using object-oriented techniques, that include intensive use of classes, exception handling and design patterns, as well as a clear division of tasks.

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“…The MMT and LBT shells have been polished with the stressed laps technology developed by the Mirror Lab (Martin et al , 2006. We propose here an aspherisation method based on the bending of the mirror itself instead of the lap during polishing with a full sized spherical lap.…”

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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Deformable secondary mirrors for the LBT adaptive optics system

Cited by 23 publications

References 10 publications

Optical figuring specifications for thin shells to be used in adaptive telescope mirrors

Optical figuring specifications for thin shells to be used in adaptive telescope mirrors

The LBT-AdOpt arbitrator: coordinating many loosely coupled processes

Stress polishing of thin shells for adaptive secondary mirrors

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