Transcript Point Image
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 00.3
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