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Page 1 Adaptive Optics and its Applications Lecture 1 Claire Max UC Santa Cruz January 8, 2013 Neptune with and without AO.

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Presentation on theme: "Page 1 Adaptive Optics and its Applications Lecture 1 Claire Max UC Santa Cruz January 8, 2013 Neptune with and without AO."— Presentation transcript:

1 Page 1 Adaptive Optics and its Applications Lecture 1 Claire Max UC Santa Cruz January 8, 2013 Neptune with and without AO

2 Page 2 ASTR 289 Outline of lecture Introductions, goals of this courseIntroductions, goals of this course How the course will workHow the course will work Overview of adaptive optics and its applicationsOverview of adaptive optics and its applications Please remind me to stop for a break at 2:45 pm !

3 Page 3 ASTR 289 Videoconference / teleconference techniques Please identify yourself when you speakPlease identify yourself when you speak –“This is Mary Smith from Santa Cruz” Report technical problems to Leslie Ward at If that doesn’t work, please text me at (my cell)Report technical problems to Leslie Ward at If that doesn’t work, please text me at (my cell) Microphones are quite sensitiveMicrophones are quite sensitive –Do not to rustle papers in front of them –Mute your microphone if you are making side-comments, sneezes, eating lunch, whatever –In fact, it’s probably best if you keep microphone muted until you want to ask a question or make a comment

4 Page 4 ASTR 289 Introductions: who are we? Via video: people I know about so farVia video: people I know about so far –UC Santa Barbara: Seth Meeker (Physics) –UC San Francisco: Nikhil Pandey (Ophthalmology) –U. Arizona: Johanna Teske (Astro) and Jihun Kim (Optics) –Subaru Observatory: Christophe Clergeon and Garima Singh –Keck Observatory: Pete Tucker, Greg Doppman, Luca Rizzi, Randy Campbell, Bob Goodrich –Univ. of Rochester: Jim Fienup (Optics)

5 Page 5 ASTR 289 Who are we? continued In the CfAO conference room at UCSC:In the CfAO conference room at UCSC: –Zach Jennings –Matthew Kissel –Vanessa Molletti –Alex Rudy –Tuguldur Sukhbold (not here today)

6 Page 6 ASTR 289 Goals of this course To understand the main concepts and components behind adaptive optics systemsTo understand the main concepts and components behind adaptive optics systems To understand how to do astronomical observations with AOTo understand how to do astronomical observations with AO To get acquainted with AO components in the LabTo get acquainted with AO components in the Lab Introduction to non-astronomical applications, mainly vision scienceIntroduction to non-astronomical applications, mainly vision science I hope to interest a few of you in learning more AO, and doing research in the fieldI hope to interest a few of you in learning more AO, and doing research in the field

7 Page 7 ASTR 289 Course websites Main: –Lectures will be on web before each class –Homework assignments (and, later, solutions) –Reading assignments Auxiliary: e-CommonsAuxiliary: e-Commons https://ecommons.ucsc.edu/xsl-portal/site/20c6ce2f-5a58-4ca8-a4a5- 86f38ccd68b7/page/a324d1ce-a00e c8-560c68c36dac https://ecommons.ucsc.edu/xsl-portal/site/20c6ce2f-5a58-4ca8-a4a5- 86f38ccd68b7/page/a324d1ce-a00e c8-560c68c36dac –Will be used for copyright-protected material –UCSC students: use your Gold login –Others: You will have to sign up first. I will tell you how via . Meantime I’ll readings to you –You will need a password

8 Page 8 ASTR 289 Required Textbook Adaptive Optics for Astronomical Telescopes by John W. Hardy (Oxford University Press) I will post pdf files of other reading assignments on the e-Commons website –I will the pdfs to those of you who don’t yet have e-Commons access

9 Page 9 ASTR 289 Outline of lecture Introductions, goals of this courseIntroductions, goals of this course How the course will workHow the course will work Overview of adaptive opticsOverview of adaptive optics

10 Page 10 ASTR 289 Course components LecturesLectures Reading assignmentsReading assignments Homework problemsHomework problems ProjectProject Laboratory exercisesLaboratory exercises Final examFinal exam (Possible field trip to Lick Observatory?)(Possible field trip to Lick Observatory?)

11 Page 11 ASTR 289 How People Learn Researchers studying how people learn have shown that the traditional passive lecture is far from the most effective teaching tool.Researchers studying how people learn have shown that the traditional passive lecture is far from the most effective teaching tool. It is not possible for an instructor to pour knowledge into the minds of students.It is not possible for an instructor to pour knowledge into the minds of students. It is the students who must actively engage in the subject matter in a manner that is meaningful to them.It is the students who must actively engage in the subject matter in a manner that is meaningful to them. Hence this course will use several departures from the traditional lecture format, to encourage active learning and understanding of concepts rather than memorization of formulas and details.Hence this course will use several departures from the traditional lecture format, to encourage active learning and understanding of concepts rather than memorization of formulas and details.

12 Page 12 ASTR 289 Concept Questions Lectures will discuss the underlying concepts and key points, elaborate on reading, and address difficulties.Lectures will discuss the underlying concepts and key points, elaborate on reading, and address difficulties. –I will assume you have already done a first pass through the reading As feedback to me, lectures will include Concept QuestionsAs feedback to me, lectures will include Concept Questions You will be asked to first formulate your own answer, then to discuss your answer with each other, and finally to report each group’s answers to the class as a whole.You will be asked to first formulate your own answer, then to discuss your answer with each other, and finally to report each group’s answers to the class as a whole.

13 Page 13 ASTR 289 Ideas from “Peer Instruction” by Eric Mazur A physics professor at HarvardA physics professor at Harvard Documented the fact that students don’t learn much from a regular lectureDocumented the fact that students don’t learn much from a regular lecture Students need to be more actively engagedStudents need to be more actively engaged Students learn best from each otherStudents learn best from each other

14 Page 14 ASTR 289 Reading Assignments I will expect you to do the reading BEFORE classI will expect you to do the reading BEFORE class Then if you want, go back and read more deeply after the lecture, to resolve areas which seem confusingThen if you want, go back and read more deeply after the lecture, to resolve areas which seem confusing From time to time I will give small “Reading Quizzes” at the start of a class, where I ask three questions that you’ll be able to answer easily if you’ve spent even 30 minutes looking at the reading assignmentFrom time to time I will give small “Reading Quizzes” at the start of a class, where I ask three questions that you’ll be able to answer easily if you’ve spent even 30 minutes looking at the reading assignment

15 Page 15 Inquiry Labs: Designed by grad students in our Professional Development Program AO DemonstratorAO Demonstrator Learning goals:Learning goals: –3 main components of AO system –Ray-trace diagram –Optical conjugation –Focus and magnification –Alignment techniques –Performance of AO system Fourier Optics (maybe)Fourier Optics (maybe) Learning goals:Learning goals: –Pupil plane and focal plane –Relationship between aperture and PSF –Phase errors and effects, including speckles –Wavefront error and Shack-Hartmann spots Would be best if out-of-town students could travel to UCSC for these; otherwise we will arrange alternate learning experiences

16 Page 16 Project: Design an AO system to meet your chosen scientific goals Learning goals:Learning goals: –Systems thinking –Requirements-driven design –Optimization and tradeoffs –Wavefront error terms and error budget Activity outline:Activity outline: –Choose a science goal –Sketch out the design of an AO system that best meets your science goal –Justify design decisions with an error budget –Present your design ASTR 289

17 Page 17 ASTR 289 A “textbook in the process of being written” I’ve been asked to write an AO textbook by Princeton University PressI’ve been asked to write an AO textbook by Princeton University Press I’ll be writing up some of the lectures as backbone for textbook chapters; I’ll ask for your feedbackI’ll be writing up some of the lectures as backbone for textbook chapters; I’ll ask for your feedback I’ll be asking for your help with homework problemsI’ll be asking for your help with homework problems –For problems that I assign to you, tell me what works, what doesn’t –From time to time, I’ll ask YOU to develop a homework problem, and then answer it –Sometimes I’ll ask you to trade problems, so each person does a problem that someone else came up with

18 Page 18 ASTR 289 Homework for Thursday Jan 10th (see website for details) Read Syllabus carefully (dowload from class website)Read Syllabus carefully (dowload from class website) Do Homework # 1: “Tell me about yourself”Do Homework # 1: “Tell me about yourself” –Specific questions on web, won’t take long – your responses to me from your favorite address, so I’ll know how to reach you –Always make the subject line “289” so I won’t lose your Reading assignment:Reading assignment: –Geometrical Optics (see website for details)

19 Page 19 ASTR 289 Outline of lecture Introductions, goals of this courseIntroductions, goals of this course How the course will workHow the course will work Overview of adaptive opticsOverview of adaptive optics

20 Page 20 ASTR 289 Why is adaptive optics needed? Even the largest ground-based astronomical telescopes have no better resolution than an 8" telescope! Even the largest ground-based astronomical telescopes have no better resolution than an 8" telescope! Turbulence in earth’s atmosphere makes stars twinkle More importantly, turbulence spreads out light; makes it a blob rather than a point

21 Page 21 ASTR 289 Images of a bright star, Arcturus Lick Observatory, 1 m telescope Long exposure image Short exposure image Image with adaptive optics Speckles (each is at diffraction limit of telescope) θ ~ 1 arc sec θ ~  / D

22 Page 22 ASTR 289 Turbulence changes rapidly with time “Speckle images”: sequence of short snapshots of a star, taken at Lick Observatory using the IRCAL infra-red camera Centroid jumps around (image motion) Image is spread out into speckles

23 Page 23 ASTR 289 Turbulence arises in many places stratosphere tropopause Heat sources w/in dome boundary layer ~ 1 km km wind flow over dome

24 Page 24 ASTR 289 Plane Wave Distorted Wavefront Atmospheric perturbations cause distorted wavefronts Index of refraction variations Rays not parallel

25 Page 25 ASTR 289 Optical consequences of turbulence Temperature fluctuations in small patches of air cause changes in index of refraction (like many little lenses)Temperature fluctuations in small patches of air cause changes in index of refraction (like many little lenses) Light rays are refracted many times (by small amounts)Light rays are refracted many times (by small amounts) When they reach telescope they are no longer parallelWhen they reach telescope they are no longer parallel Hence rays can’t be focused to a point:Hence rays can’t be focused to a point: Parallel light rays Light rays affected by turbulence Blur Point focus

26 Page 26 ASTR 289 Imaging through a perfect telescope With no turbulence, FWHM is diffraction limit of telescope, θ ~  / D Example:  / D = 0.02 arc sec for  = 1  m, D = 10 m With turbulence, image size gets much larger (typically arc sec) FWHM ~  /D in units of  /D 1.22  /D Point Spread Function (PSF): intensity profile from point source

27 Page 27 ASTR 289 Characterize turbulence strength by quantity r 0 “Coherence Length” r 0 : distance over which optical phase distortion has mean square value of 1 rad 2 (r 0 ~ cm at good observing sites) “Coherence Length” r 0 : distance over which optical phase distortion has mean square value of 1 rad 2 (r 0 ~ cm at good observing sites) r 0 = 10 cm  FWHM = 1 arc sec at  = 0.5 μmr 0 = 10 cm  FWHM = 1 arc sec at  = 0.5 μm Primary mirror of telescope r0r0r0r0 “Fried’s parameter” Wavefront of light

28 Page 28 ASTR 289 Effect of turbulence on image size If telescope diameter D >> r 0, image size of a point source is  / r 0 >>  / DIf telescope diameter D >> r 0, image size of a point source is  / r 0 >>  / D r 0 is diameter of the circular pupil for which the diffraction limited image and the seeing limited image have the same angular resolution.r 0 is diameter of the circular pupil for which the diffraction limited image and the seeing limited image have the same angular resolution. Any telescope with diameter D > r 0 has no better spatial resolution than a telescope for which D = r 0 (!)Any telescope with diameter D > r 0 has no better spatial resolution than a telescope for which D = r 0 (!)  / r 0 “seeing disk”  / D

29 Page 29 ASTR 289 How does adaptive optics help? (cartoon approximation) Measure details of blurring from “guide star” near the object you want to observe Calculate (on a computer) the shape to apply to deformable mirror to correct blurring Light from both guide star and astronomical object is reflected from deformable mirror; distortions are removed

30 Page 30 ASTR 289 Infra-red images of a star, from Lick Observatory adaptive optics system With adaptive optics No adaptive optics Note: “colors” (blue, red, yellow, white) indicate increasing intensity

31 Page 31 ASTR 289 Adaptive optics increases peak intensity of a point source Lick Observatory No AO With AO No AO With AO Intensity

32 Page 32 ASTR 289 AO produces point spread functions with a “core” and “halo” When AO system performs well, more energy in coreWhen AO system performs well, more energy in core When AO system is stressed (poor seeing), halo contains larger fraction of energy (diameter ~ r 0 )When AO system is stressed (poor seeing), halo contains larger fraction of energy (diameter ~ r 0 ) Ratio between core and halo varies during nightRatio between core and halo varies during night Intensity x Definition of “Strehl”: Ratio of peak intensity to that of “perfect” optical system

33 Page 33 ASTR 289 Schematic of adaptive optics system Feedback loop: next cycle corrects the (small) errors of the last cycle

34 Page 34 ASTR 289 How to measure turbulent distortions (one method among many) Shack-Hartmann wavefront sensor

35 Page 35 ASTR 289 How a deformable mirror works (idealization) BEFORE AFTER Incoming Wave with Aberration Deformable Mirror Corrected Wavefront

36 Deformable Mirror for Real Wavefronts

37 Page 37 ASTR 289 Real deformable mirrors have smooth surfaces In practice, a small deformable mirror with a thin bendable face sheet is usedIn practice, a small deformable mirror with a thin bendable face sheet is used Placed after the main telescope mirrorPlaced after the main telescope mirror

38 Page 38 ASTR 289 Deformable mirrors come in many sizes 30 cm MEMS 1000 actuators 1 cm Glass facesheet 1000 actuators Adaptive Secondary Mirrors Xinetics U Arizona Boston Micro- Machines

39 Incident wavefront Shape of Deformable Mirror Corrected wavefront Credit: J. Lloyd

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41 Page 41 ASTR 289 If there’s no close-by “real” star, create one with a laser Use a laser beam to create artificial “star” at altitude of 100 km in atmosphereUse a laser beam to create artificial “star” at altitude of 100 km in atmosphere

42 Page 42 ASTR 289 Laser guide stars are operating at Lick, Keck, Gemini N & S, VLT, Subaru, Palomar Three lasers on Mauna Kea: Keck 2, Gemini, Subaru telescopes

43 Page 43 ASTR 289 Keck laser guide star AO Best natural guide star AO Galactic Center with Keck laser guide star (GC is location of supermassive black hole) Source: UCLA Galactic Center group

44 Page 44 ASTR 289 Adaptive optics system is usually behind the main telescope mirror Example: AO system at Lick Observatory’s 3 m telescopeExample: AO system at Lick Observatory’s 3 m telescope Support for main telescope mirror Adaptive optics package below main mirror

45 Page 45 ASTR 289 Lick adaptive optics system at 3m Shane Telescope Off-axis parabola mirror Wavefront sensor IRCAL infra- red camera DM

46 Page 46 ASTR 289 Adaptive optics makes it possible to find faint companions around bright stars Two images from Palomar of a brown dwarf companion to GL 105 Credit: David Golimowski 200” telescope No AO With AO

47 Page 47 ASTR 289 The Keck Telescopes Adaptive optics lives here

48 Page 48 ASTR 289 Keck Telescope’s primary mirror consists of 36 hexagonal segments Nasmyth platform Person!

49 Page 49 ASTR 289 Neptune at 1.6 μm: Keck AO exceeds resolution of Hubble Space Telescope HST – NICMOS Keck AO (Two different dates and times) 2.4 meter telescope 10 meter telescope ~ 2 arc sec

50 Page 50 ASTR 289 Uranus with Hubble Space Telescope and Keck AO HST, Visible Keck AO, IR L. Sromovsky Lesson: Keck in near IR has ~ same resolution as Hubble in visible

51 Page 51 ASTR 289 Some frontiers of astronomical adaptive optics Current systems (natural and laser guide stars):Current systems (natural and laser guide stars): –How can we measure the Point Spread Function while we observe? –How accurate can we make our photometry? astrometry? Future systems:Future systems: –Can we push new AO systems to achieve very high contrast ratios, to detect planets around nearby stars? –How can we achieve a wider AO field of view? –How can we do AO for visible light (replace Hubble on the ground)? –How can we do laser guide star AO on future 30-m telescopes?

52 Page 52 ASTR 289 Frontiers in AO technology New kinds of deformable mirrors with > 5000 degrees of freedomNew kinds of deformable mirrors with > 5000 degrees of freedom Wavefront sensors that can deal with this many degrees of freedomWavefront sensors that can deal with this many degrees of freedom Innovative control algorithmsInnovative control algorithms “Tomographic wavefront reconstuction” using multiple laser guide stars“Tomographic wavefront reconstuction” using multiple laser guide stars New approaches to doing visible-light AONew approaches to doing visible-light AO

53 Page 53 ASTR 289 Other AO applications BiologyBiology –Imaging the living human retina –Improving performance of microscopy (e.g. of cells) Free-space laser communications (thru air)Free-space laser communications (thru air) Imaging and remote sensing (thru air)Imaging and remote sensing (thru air)

54 Page 54 ASTR 289 Why is adaptive optics needed for imaging the living human retina? Around edges of lens and cornea, imperfections cause distortionAround edges of lens and cornea, imperfections cause distortion In bright light, pupil is much smaller than size of lens, so distortions don’t matter muchIn bright light, pupil is much smaller than size of lens, so distortions don’t matter much But when pupil is large, incoming light passes through the distorted regionsBut when pupil is large, incoming light passes through the distorted regions Results: Poorer night vision (flares, halos around streetlights). Can’t image the retina very clearly (for medical applications)Results: Poorer night vision (flares, halos around streetlights). Can’t image the retina very clearly (for medical applications) Edge of lens Pupil

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56 Page 56 ASTR 289 Adaptive optics provides highest resolution images of living human retina Without AO With AO: Resolve individual cones (retina cells that detect color) Austin Roorda, UC Berkeley

57 Page 57 ASTR 289 Watch individual blood cells flow through capillaries in the eye

58 Page 58 ASTR 289 AO Applied to Free-Space Laser Communications 10’s to 100’s of gigabits/sec10’s to 100’s of gigabits/sec Example: AOptixExample: AOptix Applications: flexibility, mobilityApplications: flexibility, mobility –HDTV broadcasting of sports events –Military tactical communications

59 Page 59 ASTR 289 Enjoy!Enjoy!


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