Active Optics

Wilson, Raymond N.; Franza, F.; Noethe, L.

doi:10.1080/09500348714550501

Cited by 123 publications

(18 citation statements)

References 11 publications

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“…With the construction of the 3.5-m ESO-NTT, Wilson et al [21,22] pioneered new concepts to achieve the best possible image quality during observations with large telescopes. The thickness of the primary mirror is much thinner than usual, with an aspect-ratio t/D = 1/15, thus allowing in situ reshaping by a set of support actuators.…”

Section: Meniscus In Situ Reshaping and Telescope Alignment Controlmentioning

confidence: 99%

Active optics with a minimum number of actuators

Lemaitre

2014

Advanced Optical Technologies

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Optics for astronomy implies powerful developments of active and adaptive optics methods applied to instrumentation from X-rays to the near infrared for the design of telescopes, spectrographs, and coronagraph planet finders. This presentation particularly emphasizes the development of active optics methods. Highly accurate and remarkably smooth surfaces from active optics methods allow new optical systems that use highly aspheric and non-axisymmetric -freeform -surfaces. Depending on the goal and performance required for a deformable optical surface, elasticity theory analysis is carried out either with small deformation thin plate theory, large deformation thin plate theory, shallow spherical shell theory, or the weakly conical shell theory. A mirror thickness distribution is then determined as a function of associated bending actuators and boundary conditions. For a given optical shape to generate, one searches for optical solutions with a minimum number of actuators.

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Section: Meniscus In Situ Reshaping and Telescope Alignment Controlmentioning

confidence: 99%

Active optics with a minimum number of actuators

Lemaitre

2014

Advanced Optical Technologies

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“…Curvature WFS has been used in telescope testing 9 . M1 segment relative Piston and Tilt can be estimated from the curvature signal has it is shown by Cuevas et al 10 .…”

Section: Introductionmentioning

confidence: 99%

The commissioning instrument for the Gran Telescopio Canarias: made in Mexico

et al. 2006

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In March 2004 was accepted in the site of Gran Telescopio Canarias (GTC) in La Palma Island, Spain, the Commissioning Instrument (CI) for the GTC. During the GTC integration phase, the CI will be a diagnostic tool for performance verification. The CI features four operation modes-imaging, pupil imaging, Curvature Wave-front sensing (WFS), and high resolution Shack-Hartmann WFS. This instrument was built by the Instituto de Astronomía UNAM in México City and the Centro de Ingeniería y Desarrollo Industrial (CIDESI) in Querétaro, Qro under a GRANTECAN contract after an international public bid. Some optical components were built by Centro de Investigaciones en Óptica (CIO) in León Gto and the biggest mechanical parts were manufactured by Vatech in Morelia Mich. In this paper we made a general description of the CI and we relate how this instrument, build under international standards, was entirely made in Mexico.

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“…Since the success of Active Optics at NTT and VLT (Wilson et al 1987(Wilson et al , 1991, the world's largest telescopes have integrated active mirrors in their design, which improves their performance. But the new scientific objectives of the astronomical community from cosmology to exoplanets detection require telescopes and instrumentation with an ever better performance, either for ground-based astronomy or in space.…”

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

Cited by 123 publications

References 11 publications

Active optics with a minimum number of actuators

Active optics with a minimum number of actuators

The commissioning instrument for the Gran Telescopio Canarias: made in Mexico

Stress polishing of thin shells for adaptive secondary mirrors

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