Adaptive Optics: basic concepts, principles and applications Short course of lectures

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Adaptive Opticsbasic concepts, principles and
applications Short course of lectures

• Vadim Parfenov
• Res.Ctr. S.I.Vavilov State Optical Institute
• 14, Birzhevaya linia, St.Petersburg, 199034,
  Russia
• vadim_at_optilas.spb.ru

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Lecture 2 Applications of Adaptive
Optics.New technologies. Future of AO
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Adaptive optics technology
AO technology deals with real-time correction of
optical aberrations. Used mainly in
research environment. Established
applications - Astronomy - Military optical
systems - Laser technology -
Ophthalmology.
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Part IAstronomy with Adaptive Optics
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Optical observations by ground-based astronomers
have long been limited by the distorting effects
of the Earths atmosphere. Primary mirrors of
telescopes have been polished to exquisite
accuracy for telescopes with apertures as large
as 10 meters, but at optical wavelengths these
can deliver an angular resolution typically no
better than of a 25-cm telescope, as atmospheric
turbulence deforms the image on a millisecond
time scale. Two possible solutions of the
problem1. Space Telescopes (Extremely
expensive ! )2. Adaptive Optics Systems which
measure and undo the effects of clear-air
turbulence in real time.
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I. Existing and funded Projects Some examples
of adaptive optics systems currently working for
astronomy

• -        ESO-France-Come-On-Plus system at La
  Silla Observatory, Chile
• (52 actuators on a 3.6-m
  telescope)
• (this is improved version of an
  early prototype called Come-On)
• (19 actuators on the ESO 3.6-m
  telescope))
•   -        the University of Hawaii system
  at the Canada-France-Hawaii Telescope (CFHT)
• on Mauna Kea, Hawaii, USA (12
  actuators on a 3.6-m telescope)
• - two 10-m Keck telescopes, Mauna
  Kea, Hawaii, USA (primary mirror consists of 36
  
• hexagonal elements)
• -        8.5-m Gemini North telescope
  product of a collaboration of the U.S.A., Canada,
  the United
• Kingdom, Argentina, Brazil and
  Chile), Mauna Kea, Hawaii, USA
• -        8.3-m Subaru telescope, Mauna
  Kea, Hawaii, USA
• -        a system on Sacramento Peak, New
  Mexico, USA, built by Lockheed for solar
• observations(19 tip-tilt piston
  segments, that is 38 degrees of freedom, on a
  0.7-m
• telescope)
• -        six-aperture Martini project on
  the 4.2-m William Herschel Telescope. La Palma.
• -      ALFA system (  3.6-m telescope,
  Cala Alto, Spain).

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Mount Mauna Kea, Hawaii, USA
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General view of Keck interferometer
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Telescope Subaru, Mount Mauna Kea, Hawaii
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Some military adaptive optical telescopes are
used for astronomical applications !
Trapezium region in the Orion nebula with
adaptive optics off (a) and on (b) at the H?
wavelength of 0.6564 ?m. These images were
obtained by the 1.5-m laser-guided adaptive
optics telescope at the Starfire Optical Range in
New Mexico. The central star, ?1 Orionis, was
used as the tip-tilt reference source. A majority
of the faint objects are H? sources associated
with the photoevaporating envelopes of low-mass
stars. Field of view is 41 x 41 arcsec, and
spatial resolutions is 0.4 arcsec. (Image
provided by R.Q.Fugate, Phillips Laboratory, and
P.McCullough, University of Illinois.)
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II. Where Do We Go From Here ? (Some coming and
Planning Projects of Astronomical telescopes)
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ESO OWL (100 meter class) Telescope
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ESO OWL (100 meter class) Telescope
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ESO OWL (100 meter class) Telescope
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Optical design of the ESO OWL Telescope
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Other projects of large astronomical adaptive
telescopes   1. 50-m Sweden adaptive
astronomical telescope
3. 25-m Russian Astronomical Telescope AST-25
(Project of Res.Ctr. Astrofizika, Moscow)
2. Project of 30-m optical-infrared Telescope
CELT (California Extremely Large Telescope)
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Part IINon-Astronomical Applications of
Adaptive Optics
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1. Military Adaptive Optical Systems

• Imaging optical systems (satellites surveillance,
  etc.)
• Large-size telescopes for ground-based high-power
  laser energy projection
• Large-size telescopes for space-based high-power
  laser energy projection.

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Three views of the satellite Seasat from
the U.S. Air Force Starfire Optical Range
3.5 m adaptive optical telescope (AF
Kirtland Airbase, NM) (a) through the
turbulence, (b) real time correction using
adaptive optical system, (c) post-processed
with the blind deconvolution algorithm.  
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• 2. Adaptive Optics in Ophthalmology

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• Measurement of human eye aberrations

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Background
Short-sightedness
Far-sightedness
Normal vision emmetropia
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Technology is in its Lasik Infancy

• keras (cornea)

smileusis (carving)
Keratomileusis (cornea carving)
1949 Professor Jose Ignnasio Barraquer of
Colombia first suggested and made myopic
keratomileusis.
Laser in situ keratomileusis (LASIK) is the most
recent step in the process of removing/shaping
corneal tissue. It combines well-established
surgical techniques with the precision of excimer
laser photoablation.
Although it enjoys at present great popularity
among refractive surgeons, LASIK is a still
developing procedure In terms of technique and
preoperative patient management.
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Medical Need of Human Eye Aberrations Measurement
LASIK involves creating a corneal flap so that
midstronal tissue can be ablated directly and
reshaped with an excimer laser beam. With the
knowledge of the aberrations the custom ablation
pattern to compensate for the aberrations of the
eye can be developed.
Because very little of the epithelium has been
disturbed, most patients report only a few hours
of discomfort after having LASIK vision
correction.
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Basic Layout of Wavefront Sensing For the Human
Eye
Principal scheme of Wavefront Analyzer for Human
Eye Aberration Measurement
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• Images of human eye retina made
• by Adaptive Optical System
• a)
  b)
• a) image made by AO fundus camera
• b) the same image after following
  mathematical treatment
• (Pictures have been taken with AO systems of the
  Lomonosv Moscow State University )

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Preliminary conclusions

• AO technology is effective way to image retina
• of human eye
• Effectiveness of AO approach has been
  demonstrated
• Collaboration of Russian and American scientists
  have resulted in development of first prototype
  of commercial fundus-camera
• New era of human eye diagnostics is begun.

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Human vision correction.Supervision ?

• The main idea
• Correction of human eye by means of AO-based
• spectacle lens and artificial eye implant
• Two main goals
• 1. Restoration of the accommodation ability of
  the human eye for two
• target groups with artificial eye implant
  and for elderly people
• (contact lens)
• 2. Improvement of the visual acuity over the
  natural limit
• (to be resarched).

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Adaptive spectacles
G. Vdovin, Quick focusing of imaging optics using
micro machined deformable mirrors, Opt. Comm.,
140, pp. 187-190, (1997).
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Preliminary conclusions

• Common knowledge
• AO is applicable to the human eye and can
  increase the resolution of its optics
• AO should be conjugated to the eye lens,
  resulting in bulky and complicated setups
• Proposed
• The only way to use AO for everyday vision
  correction is the incorporation of the AO within
  the human eye.
• There are two ways to incorporate the AO a
  contact lens and an intra-ocular implant.

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Approach
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Requirements to the implant

• Safe (low power low voltage)
• Small and bio-compatible, chemically neutral
• Wireless control and feedback
• Temporal stability
• Transparent
• Polarization insensitive
• Usable with the control system off
• Transparent for oxygen (contact lens only).

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Adaptive LC correctors
Adaptive LC correctors small (5 to 10 mm), low
power (less than 1 mW), safe, non-toxic,
transparent (90), usable with power off (no
focusing power), durable.
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Adaptive LC lens
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Suggested implant configuration

• Integrated receiver
• coil
• Integrated LC lens
• Encapsulation
• same as for
• ocular implants
• Focusing power
• controlled by the
• amplitude and
• frequency of the
• control signal
• With no control
• acts as a static
• implant

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Preliminary conclusionsWhat is required for
AO human vision correction ?

• Development of a multi-channel wireless link to
  the implantable adaptive corrector
• Development of the packaging approach for a LC
  corrector, both for the contact lens
  implementation and for the implant
• Development of a wireless-powered and controlled
  smart adaptive optical component.

The technical goals are feasible in a wider sense
than the final application-specific goals. They
are in the streamline of the general development
of the AO technology.
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• Other applications
• of Adaptive Optics

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3. Transmission of high-power energy in space
Multi-modular adaptive optical
system 1- laser beam phase modulator 2-
amplifier, 3-phase sensor, 4- collimating
telescope, 5 -frequency control, 6 - laser master
oscillator, 7 - laser-heterodyne
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4. Adaptive Optics power beaming for orbital
debris removal

• What is a problem ?
• More than 160,000 or more objects larger than
• 1 cm in diameter in low-earth orbit.
• Space debris can damage spacecrafts !
• But all space debris of the 1-10 cm can be
  removed by
• sufficient power ablating of ground-based pulsed
  lasers.
• AO system for laser beaming through atmosphere
• is necessary !

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5. Deployable Space-Based LIDARs

• Some examples
• 1. 3-meter ORACLE (joint project of the NASA
• and Canadian Space Agency)
• Goal of the project monitoring of Earth ozone
  Layer.
• 2. 3.5-meter Tektonika-A (project of Russian
• Academy of Sciences)
• Goal of the project prevention of earthquakes.

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6. Compensation of wavefront aberrationsof
high-power laser beams

• First works were carried out by Russian
  scientists
• Yu.Ananyev (Vavilov State Optical Institute),
• M.Vorontsov A.Kudryashov (Moscow State
  University)
• The goals are
• 1. Compensation of distortions of wavefront of
  high-power
• industrial lasers
• 2. Achievement of Super-Gaussian distribituion of
  laser beams

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Correction of wave-front distortions of laser
beams by means of the use of deformable mirrors
                                                
                             The intensity
distribution of high-power NdYAG laser in the
focal plane of lens overall size of the focal
spot of corrected beam decreases by 3 times !
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7. Scanning optical microscope
Micromachined deformable mirror significantly
improves the scan resolution over the wide field
of view in the scanning microscope.
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8. Adaptive pulse compression using micromachined
deformable mirrors
Application of MMDM allows to compress the laser
pulse from 150fs to about 15fs (close to the
theoretical limit). Currently one of the most
used methods of laser pulse compression.
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Preliminary conclusions

• Now there are many applications of Adaptive
  Optics !
• At present time there are several established
• applications
• - Astronomy
• - Military optical optical imaging and
  high-power
• laser beaming systems
• - Laser technology
• - Ophthalmology.

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Part III. Future of Adaptive Optics

• New approaches ?
• New technologies ?
• New applications ?

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New Technologies

• 1. MEMS-based Adaptive Optics
• 2. Membrane mirrors for space-
• based optical telescopes

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MOEMS-based Adaptive OpticsWhy MOEMS ?

• Extremely large optical telescopes, ranging
  from 20 to 100 m are currently under development
  in different research groups around the world.
  For these telescopes the number of actuators for
  each deformable mirror, roughly equal to the
  number of r0 elements within the pupil, will
  range from 5000 to 100 000.
• This number of actuators is prohibitive for
  conventional technology (stacked piezoelectric
  actuators, bimorph mirrors), but can be achieved
  by the development of new technologies based on
  optical micro-electro-mechanical systems (MOEMS).

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Why MOEMS? (2)

• Three technologies apart are expensive. Single
  framework makes it simpler and cheaper to use.
• The precision of the structures is comparable
  to the light wavelength (3501600nm)

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Micromachined MembraneDeformable Mirrors
The shape of tensed membrane is controlled by the
electrostatic attraction to the grid of electrodes
(developed by G.Vdovin, Delft Technical
University, Netherlands)
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Advantages of MOEMS-based Adaptive Optics System

• Desired features
• compactness (low weight, small size)
• simplicity (easy calibration and operation)
• speed (system frequency gt 100 Hz)
• low cost (larger scope of applications).

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New Approaches
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Radio plasma based artificial guide star as
reference beacon for adaptive astronomical
telescopes

• 1. E.Ribak, Tomographic measurement of the
  atmosphere by artificial plasma fringes, European
  Southern Observatory Proceeding 55, 186-91
  (1997).
• 2. E Ribak, Alternative artificial guide stars
  for adaptive optics. SPIE 3353, 320-9 (1998).

Radio Guide Stars can be used for global tilt
solution in optical and radio astronomical
telescopes ! E.Ribak, R.Ragazzoni, and
V.A.Parfenov, Radio plasma fringes as guide
stars tracking the global tilt, Proceedings of
SPIE, Vol. 4338, p.118-126, (2000).  
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30-meter Diameter Diffraction-Limited Gossamer
Telescopes in Space
Membrane (inflatable) mirror technology is
under development at the U.S. Air-Force Research
Laboratory
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Deployable membrane mirror in space (artistic
view)
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Adaptive Optics space- and ground-based
astronomical hypertelescopes

• Large hypertelescopes multi-aperture
  densified-pupil imaging interferometers. Consist
  of hundreds or thousands of mirror elements
  across a square kilometer or even 10 km.
• Goal general astro-physical imaging of
• deep-Universe galaxies.
• Proposed by Antonie Laberyie
• (in Adaptive Optics, ESO Conference and
  Workshop Proceedings,
• No. 58, p.109-111. (2002) )

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Conclusions

• AO is very promising optical technology which
  can be
• applicable to the astronomical telescopes and
  optical
• imaging systems and can increase the resolution
  of its
• optics.
• There are many established applications of
  Adaptive Optics.
• Now a number of new technologies and innovative
  concepts
• are under development. It will result in further
  improvement of
• Adaptive optical systems parameters.
• Further development and wide use of AO will
  depend
• on cost of AO systems.

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Future of Adaptive Optics is almost unlimited