Adaptive Optics
A Short Presentation
of
Ongoing AO Work
at Lund Observatory
Mette Owner-Petersen
Lund Observatory
Workshop for “Forskarskolen i Rymdteknik”
Gothenburg 12/9 – 13/9 Gothenburg
What is Adaptive Optics?
Answer:
Real-time Improvement of the Quality of Images which
are degraded due to dynamical perturbations of the
imaging system
What is Meant by Image Quality?
1
Peak Intensity (Strehl Ratio)
Point Image
(PSF)
Strehl Ratio
0.8
0.6
Resolution (FWHM)
FWHM
0.4
0.2
Contrast (Background Level)
Background
-10
-5
0
Strehl Ratio:
Detection of faint objects
FWHM:
Resolving bright objects in crowded fields
Contrast:
Direct Exo-Planet observation
5
10
A Generic Example of Adaptive Optics
The Shack-Hartmann Wavefront Sensor
Other design principles are possible
How it looks in Reality
From the William Herschel telescope on La Palma
With and Without Adaptive Optics
Different AO Modes
Single Conjugate Adaptive Optics (SCAO).
One DM and one guide star -> High Strehl but small corrected field.
Ground Layer Adaptive Optics (GLAO). The easy game.
One DM and several guide stars -> Low Strehl but narrow FWHM over large field.
Multi Conjugate Adaptive Optics (MCAO).
Several DMs and several guide stars -> High Strehl and large corrected field.
Extreme Adaptive Optics (ExAO). The hard bargain
One DM and one Guide Star. Complicated filtering in both image and pupil plane
-> Extremely high contrast.
SCAO versus MCAO
Uncorrected
SCAO
MCAO
How to Make it Work
Analytical performance evaluation
Confirmation by simulations
Lab verifications if needed
Optical modeling
“The real thing”
Ongoing AO Work
Simulations of AO perfomance for the Euro50. Integrated modeling
PhD project for Anita Enmark
DCAO on the Lunda – Moon and for terrestrial applications
Collaboration with Dept. of Applied Optics in Galway and FOI Sweden
PhD project for Per Knutsson
DCAO for wide - field retinal imaging
Collaboration with Dept. of Ophthalmology in Gothenburg
Previous: Analytical performance evaluations
Experimental verification of expected DCAO performance
Correction for Atmosphere
La Palma 7-Layer Model
Euro50 PSF @ λ=2.2 μm Scale 00.3
0 s < t < 0.1 s No AO correction
0.1 s < t < 0.6 s Slow correction for Focus & Tip/tilt
0.6 s < t < 1.1 s AO ON
Specification for AO: Strehl > 0.58
The Moon DCAO Experiment
WFS
Sci. Cam.
DM1
0 km
DM2
10 km
Tip /Tilt
Zemax Model
Celestron
S-H pattern
Subimage
Wide Field Retinal Imaging
First light very soon!
The Lund DCAO Demonstrator
Goal of the experiment: Emulation of K – band performance
of SCAO, GLAO and DCAO on a 7.5 m telescope
5 guide stars in a cross
Specific Address:
Field gain going from SCAO to DCAO
The Lund DCAO Demonstrator