Transcript Adaptive Optics: basic principles and applications Short

Adaptive Optics:
basic 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
[email protected]
Lecture #2
Applications of Adaptive
Optics.
New technologies.
Future of AO
Outline
• Astronomy with Adaptive Optics;
• Non-Astronomical Applications of AO;
• Adaptive Optics in Ophtalmology;
• Other Applications of AO;
• New Technologies;
• Future of AO.
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.
Part I
Astronomy with
Adaptive Optics
Optical observations by ground-based astronomers
have long been limited by the distorting effects of the Earth’s
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 problem:
1. Space Telescopes (Extremely expensive ! );
2. Adaptive Optics Systems which measure and
undo the effects of clear-air turbulence in real
time.
I. Existing and funded Projects
Some examples of adaptive optics systems currently
working for astronomy:
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-
-
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).
Mount Mauna Kea, Hawaii, USA
KECK INTERFEROMETER
General view of Keck interferometer
KECK TELESCOPE
PRIMARY MIRROR
Telescope Subaru, Mount Mauna Kea, Hawaii
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.)
II. Where Do We Go From Here ?
(Some coming and Planning Projects
of Astronomical telescopes)
ESO OWL (100 meter – class) Telescope
ESO OWL (100 meter – class) Telescope
ESO OWL (100 meter – class) Telescope
Optical design of the ESO OWL Telescope
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)
THE JAMES WEBB SPACE TELESCOPE
JWST (formerly Next Generation Space telescope) will be a large,
infrared-optimized adaptive space telescope.
It will have an 18-segment, 6.5-meter primary mirror.
It is being built by Northrop Grumman Space Technology
and is scheduled to launch in 2011.
Part II
Non-Astronomical
Applications of
Adaptive Optics
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.
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.
2. Adaptive Optics in
Ophthalmology
Historical remarks
• First investigations on the use of AO in
ophthalmology have been carried out by David
Williams from Rochester University, USA,
in 1995-1996.
• First prototype of commercial AO fundus camera –
result of joint researches of the Moscow State
University, Russia (project manager –
Dr. A.Larichev) & Kestrel Corp., USA, (project
manager – Dr.L.John Otten) - 2002.
Measurement of human eye
aberrations
Background
Short-sightedness
Normal vision = emmetropia
Far-sightedness
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.
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.
Basic Layout of Wavefront
Sensing For the Human Eye
1
8
L6
4
7
3
3
3
8 L9
2
3
L5
9
L4
Б
L7
L3
8
11
A
L2
8
L8
4
Г
L1
12
6
L10
5
32
14
13
В
10
Principal scheme of Wavefront Analyzer for
Human Eye Aberration Measurement
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 )
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.
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).
Adaptive spectacles
G. Vdovin, Quick focusing of imaging optics using micro
machined deformable mirrors, Opt. Comm., 140,
pp. 187-190, (1997).
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.
Approach
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).
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.
Adaptive LC lens
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
Preliminary conclusions:
What 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.
Other applications
of Adaptive Optics
3. Transmission of high-power energy in space
Retransmitter
Moon
mirror
4
1
2
3
Receiver
7
6
Laser
beacon
5
Earth
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
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 !
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.
6. Compensation of wavefront aberrations
of high-power laser beams
First works were carried out by Russian scientists:
Yu.Anan`yev (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
Correction of wave-front distortions
of laser beams by means of the use of
deformable mirrors
The intensity distribution of high-power Nd:YAG laser
in the focal plane of lens
overall size of the focal spot of corrected beam decreases by 3 times !
7. Scanning optical microscope
Micromachined deformable mirror
significantly improves the scan
resolution over the wide field of
view in the scanning microscope.
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.
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.
Part III.
Future of Adaptive Optics
• New approaches ?
• New technologies ?
• New applications ?
New Technologies
1. MEMS-based Adaptive Optics
2. Membrane mirrors for spacebased optical telescopes
MOEMS-based Adaptive Optics
Why 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).
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
(350…1600nm)
Micromachined Membrane
Deformable 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)
Advantages of MOEMS-based Adaptive Optics System
imperfect
medium
Desired features:
• compactness (low weight, small size);
aberrated
wavefront
• simplicity (easy calibration and operation);
• speed (system frequency > 100 Hz);
• low cost (larger scope of applications).
adaptive mirror
computer
beam
splitter
corrected
wavefront
wavefront
sensor
image plane
New Approaches
Radio plasma based
artificial guide star
as reference beacon for
adaptive astronomical
telescopes
1.
2.
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).
30-meter Diameter Diffraction-Limited
Gossamer Telescopes in Space
Membrane (inflatable) mirror technology is under
development at the U.S. Air-Force Research Laboratory
Deployable membrane mirror in space
(artistic view)
Adaptive Optics space- and groundbased astronomical hypertelescopes
Large hypertelescopes – “multi-aperture densifiedpupil 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) )
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.
Future of Adaptive Optics
is almost unlimited…