Active Optics I
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The European Southern Observatory Your Talk
The European Southern Observatory Your talk Your name Overview What is astronomy? ESO history What is ESO? La Silla VLT ALMA E-ELT ESO Visitor Centre | 9 October 2013 Why are we here? What is astronomy? And what it all is good for? ESO Visitor Centre | 9 October 2013 What is astronomy? Astronomy is the study of all celestial objects. It is the study of almost every property of the Universe from stars, planets and comets to the largest cosmological structures and phenomena; across the entire electromagnetic spectrum and more. It is the study of all that has been, all there is and all that there ever will be. From the effects of the smallest atoms to the appearance of the Universe on the largest scales. ESO Visitor Centre | 9 October 2013 Astronomy in the ancient world Astronomy is the oldest of the natural sciences, dating back to antiquity, with its origins in the religious, mythological, and astrological practices of the ancient civilisations. Early astronomy involved observing the regular patterns of the motions of visible celestial objects, especially the Sun, Moon, stars and naked eye observations of the planets. The changing position of the Sun along the horizon or the changing appearances of stars in the course of the year was used to establish agricultural or ritual calendars. ESO Visitor Centre | 9 October 2013 Astronomy in the ancient world Australian Aboriginals belong to the oldest continuous culture in the world, stretching back some 50 000 years… It is said that they were the first astronomers. “Emu in the sky” at Kuringai National Park, Sydney -Circa unknown ESO Visitor Centre | 9 October 2013 Astronomy in the ancient world Goseck Circle Mnajdra Temple Complex c. -
Higher-Order Aberrations
Higher-order aberrations Lens Design OPTI 517 Prof. Jose Sasian Higher order Aberrations • Aberration function • Six-order terms (fifth-order transverse) • Wavefront shapes and field dependence • Coefficients • Pupil matching • References. Prof. Jose Sasian References • 1) J. Sasian, “Theory of sixth-order wave aberrations,” Applied Optics, June 2010. • 2) O. N. Stavroudis, “Modular Optical Design” • 3) Buchdahl, “Optical Aberration Coefficients” • 4) M. Herzberger, “Modern Geometrical Optics” Prof. Jose Sasian “Back of the envelope” Prof. Jose Sasian Coordinate system and reference sphere y' E ' yI H Exit pupil plane Image plane Prof. Jose Sasian Aberration function Prof. Jose Sasian Prof. Jose Sasian Aberration orders Roland Shack’s aberration diagram Prof. Jose Sasian Terminology •W240 Oblique spherical aberration •W331 Cubic coma •W422 Quartic astigmatism •W420 Six order field curvature •W511 Six order distortion •W600 Six order piston •W060 Six order spherical aberration •W151 •W242 •W333 Prof. Jose Sasian Some earlier terminology • Oblique spherical aberration • Elliptical coma • Line coma • Secondary spherical aberration • Secondary coma • Lateral coma • Lateral image curvature/astigmatism •Trefoil Prof. Jose Sasian Wavefront deformation shapes Prof. Jose Sasian Spherical aberration: W060 Prof. Jose Sasian W151 & W333 Prof. Jose Sasian W242 Prof. Jose Sasian Higher-order aberration coefficients • Harder to derive/calculate than fourth- order • Intrinsic coefficients • Extrinsic coefficients • Depend highly on coordinate system Prof. Jose Sasian Intrinsic spherical aberration 1 2 u W040 A y 8 n 2 1 y 1 u' u y 8 y W060I W040 2 A 2 u W040 W040 2 r 2 n' n r y 2 1 y 1 u' u y 8 y W060I W040 2 A 2 u' W040 W040 2 r 2 n' n r y 3 5 7 y Y y c3 y c5 y c7 y .. -
8. Adaptive Optics 299
8. Adaptive Optics 299 8.1 Introduction Adaptive Optics is absolutely essential for OWL, to concentrate the light for spectroscopy and imaging and to reach the diffraction limit on-axis or over an extended FoV. In this section we present a progressive implementation plan based on three generation of Adaptive Optics systems and, to the possible extent, the corresponding expected performance. The 1st generation AO − Single Conjugate, Ground Layer, and distributed Multi-object AO − is essentially based on Natural Guide Stars (NGSs) and makes use of the M6 Adaptive Mirror included in the Telescope optical path. The 2nd generation AO is also based on NGSs but includes a second deformable mirror (M5) conjugated at 7-8 km – Multi-Conjugate Adaptive Optics − or a post focus mirror conjugated to the telescope pupil with a much higher density of actuators -tweeter- in the case of EPICS. The 3rd generation AO makes use of single or multiple Laser Guide Stars, preferably Sodium LGSs, and should provide higher sky coverage, better Strehl ratio and correction at shorter wavelengths. More emphasis in the future will be given to the LGS assisted AO systems after having studied, simulated and demonstrated the feasibility of the proposed concepts. The performance presented for the AO systems is based on advances from today's technology in areas where we feel confident that such advances will occur (e.g. the sizes of the deformable mirrors). Even better performance could be achieved if other technologies advance at the same rate as in the past (e.g. the density of actuators for deformable mirrors). -
Position Sensing in Adaptive Optics
Position sensing in Adaptive Optics Christopher Saunter Durham University Centre for Advanced Instrumentation Durham Smart Imaging Durham Smart Imaging Active Opt ics Adappptive Optics Durham Smart Imaging Active Optics • Relaxing the mechanical rigidity of a telescope support structure • CiihillidiCompensating with actively aligned mirrors • Massive weight and cost savings over a rigid bodyyp telescope – the onlyyp practical wa y of building ELTs. • Slow – 1Hz or less Durham Smart Imaging Active Optics Sensing • Live sensing from starlight • Live sensing from a calibration source • Pre-generated look-up table of distortion vs. ppgg,pointing angle, temperature etc • CitiCritica lfl for segmen te d m irror te lescopes Durham Smart Imaging Active Optics Image credit: Robert Wagner / MAGIC / http://wwwmagic.mppmu.mpg.de/ Durham Smart Imaging Active Opt ics Adappptive Optics Durham Smart Imaging Adaptive Optics An AO system measures dynamic turbulence with a wavefront sensor and corrects it with a deformable mirror or spatial light modltdulator Durham Smart Imaging Applications of AO • Astronomy – AO is fully integral to current VLTs and future ELTs • Ophthalmology – Retinal imaging, measuring distortions • High power lasers – Intra-cavity wavefront shaping. e.g. Vulcan fusion laser (ICF) • Optical drive pickups • Microscopy • Free space optical communication • Military Durham Smart Imaging Wavefront sensors • There are many types of wavefront sensors • Shack Hartmann, Curvature, Pyramid, Point Diffraction Interferometer, Lateral Shearing -
Representation of Wavefront Aberrations
Slide 1 4th Wavefront Congress - San Francisco - February 2003 Representation of Wavefront Aberrations Larry N. Thibos School of Optometry, Indiana University, Bloomington, IN 47405 [email protected] http://research.opt.indiana.edu/Library/wavefronts/index.htm The goal of this tutorial is to provide a brief introduction to how the optical imperfections of a human eye are represented by wavefront aberration maps and how these maps may be interpreted in a clinical context. Slide 2 Lecture outline • What is an aberration map? – Ray errors – Optical path length errors – Wavefront errors • How are aberration maps displayed? – Ray deviations – Optical path differences – Wavefront shape • How are aberrations classified? – Zernike expansion • How is the magnitude of an aberration specified? – Wavefront variance – Equivalent defocus – Retinal image quality • How are the derivatives of the aberration map interpreted? My lecture is organized around the following 5 questions. •First, What is an aberration map? Because the aberration map is such a fundamental description of the eye’ optical properties, I’m going to describe it from three different, but complementary, viewpoints: first as misdirected rays of light, second as unequal optical distances between object and image, and third as misshapen optical wavefronts. •Second, how are aberration maps displayed? The answer to that question depends on whether the aberrations are described in terms of rays or wavefronts. •Third, how are aberrations classified? Several methods are available for classifying aberrations. I will describe for you the most popular method, called Zernike analysis. lFourth, how is the magnitude of an aberration specified? I will describe three simple measures of the aberration map that are useful for quantifying the magnitude of optical error in a person’s eye. -
Design and Manufacture of Mirrors, and Active Optics Buddy Martin
Design and manufacture of mirrors, and active optics Buddy Martin Steward Observatory Mirror Lab 1 Outline • What makes a good mirror? • Modern mirror concepts – thin solid mirrors – segmented mirrors – lightweight mirrors • Honeycomb mirrors – design – casting • Optical manufacture – requirements – aside on active optics and model fitting – fabrication • machining • polishing – measurement • interferometry • null correctors • GMT measurements 2 What makes a good mirror? (mechanical) • Fundamental requirement is to deliver a good wavefront to focal plane in almost all conditions. – Hold its shape to a fraction of a wavelength on large scales – Be smooth to a small fraction of a wavelength on small scales – Contribute little to local seeing (temperature gradients in air) • Stiffness against wind: bending stiffness ∝ Et3 – E = Young’s modulus, t = thickness • Stiffness against gravity: bending stiffness ∝ Et 2 / ρ – This puts a premium on low mass. cross-section of an 8.4 m honeycomb mirror for the Giant Magellan Telescope 3 What makes a good mirror? (thermal) • Thermal distortion: displacement = α ΔT t for “swelling” curvature = α ΔT / t for bending – α = thermal expansion coefficient, ΔT = temperature variation within mirror • “Mirror seeing” ∝ T − T a ir ≈ dTair dt ⋅τ – dTair/dt = rate of change of air temperature 2 – τ = mirror’s thermal time constant ∝ cρt / k • c = specific heat, k = thermal conductivity, t = thickness – Becomes a problem for T - Tair > ~0.3 K, τ > ~1 hr – For glass or glass-ceramics, want t < 5 cm • Bottom line: Mirror should be stiff & light, have low thermal expansion & short thermal time constant. 4 Optical telescopes 12 LBT 10 Keck VLT (4), Gemini (2), Subaru 8 MMT, Magellan (2) 6 Palomar 200 inch diameter (m) diameter 4 Mt. -
Download Chapter 3 Sample Pages
eyesskies_95.indd 553 2008-07-08 12:24:18 TECHNOLOGY TO 3 THE RESCUE ESO’S NEW TECHNOLOGY Progress in telescopic astronomy would have come to a grinding TELESCOPE The octagonal enclosure housing the European halt in the second half of the twentieth century if it weren’t for the Southern Observatory’s 3.6-metre New Technology digital revolution. Powerful computers have enabled a wealth of Telescope (NTT) at Cerro La Silla in northern Chile was a technological breakthrough new technologies that have resulted in the construction of giant when completed in 1989. The telescope chamber is venti- telescopes, perched on high mountaintops with monolithic or lated by a system of fl aps that makes the air fl ow smoothly segmented mirrors as large as swimming pools. Astronomers across the mirror, resulting in very sharp images. The NTT was also a testbed for have even devised clever ways of undoing the distorting effects fully computer-controlled alt-azimuth mounts, thin of atmospheric turbulence and of combining individual telescope mirrors, and active optics. mirrors into virtual behemoths with unsurpassed eyesight. The optical wizardry of 21st century telescope building has ushered in a completely new era of ground-based astronomical discovery. 45 eyesskies_95.indd 545 2008-07-08 12:23:26 “ Just as modern cars don’t look like Model T-Fords, current telescopes look very different from traditional instruments” THE NEW TECHNOLOGY Just as modern cars don’t look like Model T-Fords, current telescopes look very differ- TELESCOPE PEERS INTO A ent from traditional instruments like the 5-metre Hale Telescope. -
Adaptive Optics Facility – Control Strategy and First On-Sky Results of the Acquisition Sequence
Adaptive Optics Facility – control strategy and first on-sky results of the acquisition sequence P-Y Madec1, J. Kolb, S. Oberti, J. Paufique, P. La Penna, W. Hackenberg, H. Kuntschner, J. Argomedo, M. Kiekebusch, R. Donaldson, M. Suarez, R. Arsenault European Southern Observatory, Karl Schwarzschild Str 2, D-85748 Garching ABSTRACT The Adaptive Optics Facility is an ESO project aiming at converting Yepun, one of the four 8m telescopes in Paranal, into an adaptive telescope. This is done by replacing the current conventional secondary mirror of Yepun by a Deformable Secondary Mirror (DSM) and attaching four Laser Guide Star (LGS) Units to its centerpiece. In the meantime, two Adaptive Optics (AO) modules have been developed incorporating each four LGS WaveFront Sensors (WFS) and one tip- tilt sensor used to control the DSM at 1 kHz frame rate. The four LGS Units and one AO module (GRAAL) have already been assembled on Yepun. Besides the technological challenge itself, one critical area of AOF is the AO control strategy and its link with the telescope control, including Active Optics used to shape M1. Another challenge is the request to minimize the overhead due to AOF during the acquisition phase of the observation. This paper presents the control strategy of the AOF. The current control of the telescope is first recalled, and then the way the AO control makes the link with the Active Optics is detailed. Lab results are used to illustrate the expected performance. Finally, the overall AOF acquisition sequence is presented as well as first results obtained on sky with GRAAL. -
Flatness of Dichroic Beamsplitters Affects Focus and Image Quality
Flatness of Dichroic Beamsplitters Affects Focus and Image Quality 1. Introduction Even though fluorescence microscopy has become a routine technique for many applications, demanding requirements from technological advances continue to push the limits. For example, today biological researchers are not only interested in looking at fixed-cell samples labeled with multiple colors, but they are also interested in looking at the dynamics of live specimens in multiple colors, simultaneously. Even certain fixed-cell imaging applications are hampered by limited throughput of the conventional multicolor imaging techniques. Given that the most popular multicolor fluorescence imaging configurations – including “Sedat” and “Pinkel” [1] – are often too slow, new multicolor imaging approaches are evolving. The schematic of such an imaging setup that enables “simultaneous” visualization of multicolor images of a specimen is shown in Figure 1. Figure 1: A simple setup for simultaneous visualization of two colors. In this example, the dual-colored emission signal from the sample is split into two emission light paths using a dichroic beamsplitter, and the signal in each of these channels is imaged onto a CCD camera. An advantage of this configuration over conventional multicolored imaging configurations is that the emission signal from multiple sources can be visualized simultaneously. Due to the absence of any moving parts, such as a filter wheel, this approach enables high-speed image acquisition, thus allowing for very fast cellular dynamics to be imaged in multiple colors at the same time. The principal of splitting the emission signal into different channels is already possible using commercially available products that allow for multichannel imaging. -
Blind Optical Aberration Correction by Exploring Geometric and Visual Priors
Blind Optical Aberration Correction by Exploring Geometric and Visual Priors Tao Yue1 Jinli Suo1 Jue Wang2 Xun Cao3 Qionghai Dai1 1Department of Automation, Tsinghua University 2Adobe Research 3School of Electronic Science and Engineering, Nanjing University Abstract have also proposed various complex hardware solutions for compensating optical aberration [1,9,10,15,17,18], but the Optical aberration widely exists in optical imaging sys- requirement of using special devices limits their application tems, especially in consumer-level cameras. In contrast range, especially for consumer applications. to previous solutions using hardware compensation or pre- Given the limitations of hardware solutions, computa- calibration, we propose a computational approach for blind tionally removing optical aberration has attracted strong aberration removal from a single image, by exploring vari- interests and has been exensively studied in the past ous geometric and visual priors. The global rotational sym- decade [3–5, 12, 13]. However, most of existing aberra- metry allows us to transform the non-uniform degeneration tion correction methods [3, 5, 12] are non-blind, i.e. the into several uniform ones by the proposed radial splitting Point Spread Functions (PSFs) of the aberration need to be and warping technique. Locally, two types of symmetry calibrated beforehand. Kee et al. [5] propose a parameter- constraints, i.e. central symmetry and reflection symmetry ized model to describe the nonuniform PSFs of a zoom lens are defined as geometric priors in central and surround- at different focal lengths, so that only several calibration ing regions, respectively. Furthermore, by investigating the measurements are required to be taken. Schuler et al. -
Active Optics in Astronomy – Modeling of Deformable Substrates : Freeform Surfaces for Fireball and MESSIER
Proc. 7th Intl. Conf. on Mathematical Modeling in Physical Sciences, ICM2, State University Lomonosov, Moscow, 27-31 Aug. 2018 and, Special Issue of “Journal of the Mechanical Behavior of Materials”, De Gruyter edit., Berlin, accepted 14 Nov. 2018 Active optics in astronomy – Modeling of deformable substrates : Freeform surfaces for FIREBall and MESSIER Gerard R. Lemaitre Laboratoire d’Astrophysique Marseille - LAM, Aix Marseille Université - AMU 38 rue Fr´ed´eric Joliot-Curie, 13388 Marseille CX 13, FRANCE E-mail: [email protected] Abstract: Active optics techniques on large telescopes and astronomical instrumentations provide high imaging quality. For ground-based astronomy, the co-addition of adaptive optics again increases angular resolution up to provide diffraction-limited imaging at least in the infrared. Active and adaptive optics marked milestone progress in the detection of exoplanets, super-massive black holes, and large scale structure of galaxies. This paper is dedicated to highly deformable active optics that can generate non-axisymmetric aspheric surfaces - or freeform surfaces - by use of a minimum number of actuators: a single uniform load acts over the surface of a vase-form substrate whilst under reaction to its elliptical perimeter ring. Two such instruments are presented, 1) the FIREBall telescope and MOS where the freeform reflective diffraction grating is generated by replication of a deformable master grating, and 2) the MESSIER wide-field low-central-obstruction TMA telescope proposal where the freeform mirror is generated by stress figuring and elastic relaxation. Freeform surfaces were obtained by plane super-polishing. Preliminary analysis required use of the optics theory of 3rd-order aberrations and elasticity theory of thin elliptical plates. -
The Extremely Large Telescope Why Chile?
The Extremely Large Telescope Why Chile? Excellent conditions in the Atacama Desert Extremely dry 90% clean sky Low turbulence Excellent vision to the Southern Hemisphere (Paranal) (Chajnantor) Poor site Chile Armazones and Paranal 25 km Huge Collecting Area HST 2.4m (in space) Gemini N Keck I-II Subaru LBT Gemini S VLTs Magellan GTC HET E-ELT SALT 39m 1990 2000 2010 2020 High quality images from the ground E-ELT excels in collecting power and angular resolution 39.3m telescope with Adaptive Optics will deliver E8m-ELT Hubble Space Telescope 4.9 X better angular resolution (1/D) 510 X faster exposure time (1/D4) than existing 8m telescopes Unprecedented sensitivity and angular resolution Prepare for the unexpected…!! 5 Science • The High-redshift Universe & Galaxy Formation • Black Holes and Active Galactic Nuclei • Resolved Stellar Populations and Star Formation • Exoplanets and their Atmospheres 6 The E-ELT Design • 40-m class telescope: largest optical-infrared telescope in the world • Segmented primary mirror • Active optics to maintain collimation and mirror figure • Adaptive optics assisted telescope • Diffraction limited performance • Wide field of view: 10 arcmin 5-Mirror Design 8 The Main Structure The Main Structure is about 38 m diameter 2500 tonnes of steel moving 700 tonnes of opto-mechanics and electronics around two 65 m height perpendicular axes (azimuth and altitude) supported on hydrostatic bearings and driven by electrical direct drive motors with a precision of 0.3 arcsec under the maximum wind disturbance. 71 m width 52m diameter M1 Unit Segment Assembly 931 x M1 Segments 931 x Blanks + 19 x Spare Blanks 931 x Segments Polishing 4530 x M1 Edge Sensors 4530 x Sensors +813 x Electronics + Spares (100 sensors – 15 x controllers) 931 x M1 Segment Supports & SA Auxiliary Equipment [SA Handling Tools, SA Transport Containers, SA AIV Tools] Subcell 2394 x M1 Position Actuators 2394 x Actuators + 798 x Electronics + Spares (16 x PACT – 6 x Controllers) M1 Auxiliary Equipment Aux.