Published by De Gruyter

Volume 3 Issue 3

Issue of Advanced Optical Technologies

Contents
Journal Overview

Publicly Available June 7, 2014

Community

Publicly Available May 28, 2014

News from the European Optical Society

Page range: 209-212

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Publicly Available June 7, 2014

Conference Notes

Page range: 213-215

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Publicly Available June 7, 2014

Topical Issue: Optics for Astronomy / Guest Editors: Jan Burke, Andrew Rakich and Jim Burge

Editorial

Publicly Available June 7, 2014

Optics for astronomy – Editorial

Andrew Rakich, Jan Burke, Jim Burge

Page range: 221-222

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Review Articles

June 7, 2014

Active optics with a minimum number of actuators

Gerard R. Lemaitre

Page range: 223-249

Abstract

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.

June 7, 2014

Highly sensitive telescope designs for higher contrast observations

Gil Moretto, Jeff R. Kuhn

Page range: 251-264

Abstract

Off-axis telescope concepts that use unobstructed pupils have better emissivity, throughput, diffraction-limited energy concentrations, and higher dynamic range than traditional concentric instruments. The coronagraphic performance of off-axis telescopes will enable instruments, which are starved for higher dynamic range, for example, those devoted to faint companion detection, circumstellar and solar atmosphere studies.

Open Access May 28, 2014

Replicated spectrographs in astronomy

Gary J. Hill

Page range: 265-278

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Abstract

As telescope apertures increase, the challenge of scaling spectrographic astronomical instruments becomes acute. The next generation of extremely large telescopes (ELTs) strain the availability of glass blanks for optics and engineering to provide sufficient mechanical stability. While breaking the relationship between telescope diameter and instrument pupil size by adaptive optics is a clear path for small fields of view, survey instruments exploiting multiplex advantages will be pressed to find cost-effective solutions. In this review we argue that exploiting the full potential of ELTs will require the barrier of the cost and engineering difficulty of monolithic instruments to be broken by the use of large-scale replication of spectrographs. The first steps in this direction have already been taken with the soon to be commissioned MUSE and VIRUS instruments for the Very Large Telescope and the Hobby-Eberly Telescope, respectively. MUSE employs 24 spectrograph channels, while VIRUS has 150 channels. We compare the information gathering power of these replicated instruments with the present state of the art in more traditional spectrographs, and with instruments under development for ELTs. Design principles for replication are explored along with lessons learned, and we look forward to future technologies that could make massively-replicated instruments even more compelling.

Open Access June 7, 2014

Ultra-smooth finishing of aspheric surfaces using CAST technology

John Kong, Kevin Young

Page range: 279-291

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Abstract

Growing applications for astronomical ground-based adaptive systems and air-born telescope systems demand complex optical surface designs combined with ultra-smooth finishing. The use of more sophisticated and accurate optics, especially aspheric ones, allows for shorter optical trains with smaller sizes and a reduced number of components. This in turn reduces fabrication and alignment time and costs. These aspheric components include the following: steep surfaces with large aspheric departures; more complex surface feature designs like stand-alone off-axis-parabola (OAP) and free form optics that combine surface complexity with a requirement for ultra-high smoothness, as well as special optic materials such as lightweight silicon carbide (SiC) for air-born systems. Various fabrication technologies for finishing ultra-smooth aspheric surfaces are progressing to meet these growing and demanding challenges, especially Magnetorheological Finishing (MRF) and ion-milling. These methods have demonstrated some good success as well as a certain level of limitations. Amongst them, computer-controlled asphere surface-finishing technology (CAST), developed by Precision Asphere Inc. (PAI), plays an important role in a cost effective manufacturing environment and has successfully delivered numerous products for the applications mentioned above. One of the most recent successes is the Gemini Planet Imager (GPI), the world’s most powerful planet-hunting instrument, with critical aspheric components (seven OAPs and free form optics) made using CAST technology. GPI showed off its first images in a press release on January 7, 2014 . This paper reviews features of today’s technologies in handling the ultra-smooth aspheric optics, especially the capabilities of CAST on these challenging products. As examples, three groups of aspheres deployed in astronomical optics systems, both polished and finished using CAST, will be discussed in detail.

Open Access June 7, 2014

Hydroxide catalysis bonding for astronomical instruments

Anna-Maria A. van Veggel, Christian J. Killow

Page range: 293-307

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Abstract

Hydroxide catalysis bonding (HCB) as a jointing technique has been under development for astronomical applications since ∼1998 (patented by D.-H. Gwo). It uses an aqueous hydroxide solution to form a chemical bond between oxide or oxidisable materials (e.g., SiO 2 , sapphire, silicon and SiC). It forms strong, extremely thin bonds, and is suitable for room temperature bonding, precision alignment, operation in ultra-low vacuum and down to temperatures of 2.5 K. It has been applied in the NASA satellite mission Gravity Probe B and in the ground-based gravitational wave (GW) detector GEO600. It will soon fly again on the ESA LISA Pathfinder mission and is currently being implemented in the Advanced LIGO and Virgo ground-based GW detectors. This technique is also of considerable interest for use in other astronomical fields and indeed more broadly, due to its desirable, and adjustable, combination of properties. This paper gives an overview of how HCB has been and can be applied in astronomical instruments, including an overview of the current literature on the properties of hydroxide catalysis bonds.

Research Articles

Open Access June 7, 2014

Fabrication and metrology of lithium niobate narrowband optical filters for the solar orbiter

Stephen D. Gensemer, David Farrant

Page range: 309-314

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Abstract

We report on the fabrication of custom voltage tunable etalons for the SO/PHI spaceborne solar imaging instrument [A. Gandorfer, S. K. Solanki, J. Woch, V. M. Pillet, A. A. Herrero, and T. Appourchaux, J. Phys.: Conference Series 271, 012086 (2011)]. The etalons were manufactured to place a transmission maximum within 0.3 Å of the FeI emission line at 6175.0 Å. Meeting this specification requires an overall thickness specified to within ±15 nm, over a 60 mm aperture. We describe here the metrology, modelling and coating procedures we developed to achieve this.

June 7, 2014

A method for the use of ellipticities and spot diameters for the measurement of aberrations in wide-field telescopes

Lothar Noethe, Pietro Schipani, Ronald Holzlöhner, Andrew Rakich

Page range: 315-333

Abstract

In wide-field survey telescopes, the patterns of spot sizes and ellipticities can be used to determine wavefront aberrations generated by the telescope. The calculation of spot sizes and ellipticities generated by telescope aberrations is most conveniently done if the aberrations are expressed in terms of Zernike-type polynomials whose derivatives are orthonormal. The field dependence of the spot sizes and ellipticities generated by the telescope can conveniently be expressed by low-order Zernike polynomials. Because the exposure times in astronomical survey work are typically rather short, this information may be used for a quasi-closed loop control of the telescope optics. The ability to accurately subtract ellipticities generated by telescope errors could also be useful for observations such as gravitational lensing surveys.

June 7, 2014

Deflectometric measurement of large mirrors

Evelyn Olesch, Gerd Häusler, André Wörnlein, Friedrich Stinzing, Christopher van Eldik

Page range: 335-343

Abstract

We discuss the inspection of large-sized, spherical mirror tiles by ‘Phase Measuring Deflectometry’ (PMD). About 10 000 of such mirror tiles, each satisfying strict requirements regarding the spatial extent of the point-spread-function (PSF), are planned to be installed on the Cherenkov Telescope Array (CTA), a future ground-based instrument to observe the sky in very high energy gamma-rays. Owing to their large radii of curvature of up to 60 m, a direct PSF measurement of these mirrors with concentric geometry requires large space. We present a PMD sensor with a footprint of only 5×2×1.2 m 3 that overcomes this limitation. The sensor intrinsically acquires the surface slope; the shape data are calculated by integration. In this way, the PSF can be calculated for real case scenarios, e.g., when the light source is close to infinity and off-axis. The major challenge is the calibration of the PMD sensor, specifically because the PSF data have to be reconstructed from different camera views. The calibration of the setup is described, and measurements presented and compared to results obtained with the direct approach.

Publicly Available June 7, 2014

The Four-Laser Guide Star Facility: Design considerations and system implementation

Domenico Bonaccini Calia, Wolfgang Hackenberg, Ronald Holzlöhner, Steffan Lewis, Thomas Pfrommer

Page range: 345-361

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Abstract

Ground-based optical telescopes, in particular large ones, require adaptive optics to overcome the atmospheric seeing limit due to turbulence. Correcting the distorted wavefront necessitates bright stars in the field of view. The sky coverage can be greatly increased by using artificial sodium laser guide stars in addition to natural guide stars. We describe the underlying physics and technical considerations relevant to such systems before discussing the design of the four-laser guide star facility (4LGSF) which is currently under development for the ESO Very Large Telescope (VLT) on Cerro Paranal, Chile. The focus is upon the justification of the requirements and their technical solution.

About this journal

Objective

Advanced Optical Technologies is a strictly peer-reviewed scientific journal. The major aim of Advanced Optical Technologies is to publish recent progress in the fields of optical design, optical engineering, and optical manufacturing. Advanced Optical Technologies has a main focus on applied research and addresses scientists as well as experts in industrial research and development.

Advanced Optical Technologies partners with the European Optical Society (EOS). All its 4.500+ members have free online access to the journal through their EOS member account.

Topics

Optical design
Lithography
Opto-mechanical engineering
Illumination and lighting technology
Precision fabrication
Image sensor devices
Optical materials (polymer based, inorganic, crystalline/amorphous)
Optical instruments in life science (biology, medicine, laboratories)
Optical metrology
Optics in aerospace/defense
Simulation, interdisciplinary
Optics for astronomy
Standards
Consumer optics
Optical coatings

Article formats
Tutorial, Review Article, Research Article, Letter, Short Communication, Views

> Information on submission process

Volume 3 Issue 3

Issue of Advanced Optical Technologies

Frontmatter

News from the European Optical Society

Conference Notes

Conference Calendar

Editorial

Optics for astronomy – Editorial

Review Articles

Active optics with a minimum number of actuators

Abstract

Highly sensitive telescope designs for higher contrast observations

Abstract

Replicated spectrographs in astronomy

Abstract

Ultra-smooth finishing of aspheric surfaces using CAST technology

Abstract

Hydroxide catalysis bonding for astronomical instruments

Abstract

Research Articles

Fabrication and metrology of lithium niobate narrowband optical filters for the solar orbiter

Abstract

A method for the use of ellipticities and spot diameters for the measurement of aberrations in wide-field telescopes

Abstract

Deflectometric measurement of large mirrors

Abstract

The Four-Laser Guide Star Facility: Design considerations and system implementation

Abstract