TPF @ Princeton The Beat-Down Phenomenon in Adaptive Optics Amir Give’on Department of Mechanical...
23
TPF @ Princeton The Beat-Down Phenomenon in Adaptive Optics Amir Give’on Department of Mechanical and Aerospace Engineering, Princeton University Adviser: N.J. Kasdin Jan 2004
-
Upload
brianne-martin -
Category
Documents
-
view
217 -
download
1
Transcript of TPF @ Princeton The Beat-Down Phenomenon in Adaptive Optics Amir Give’on Department of Mechanical...
TPF @ Princeton
The Beat-Down Phenomenonin Adaptive Optics
Amir Give’onDepartment of Mechanical and Aerospace
Engineering, Princeton University
Adviser: N.J. KasdinJan 2004
TPF @ Princeton
Ever wondered why phase conjugation does not work?
Amir Give’onDepartment of Mechanical and Aerospace
Engineering, Princeton University
Adviser: N.J. KasdinJan 2004
TPF @ Princeton
Princeton TPF project(space-based)
•Contrast ratio needed: 1010
•Aberrations do not change over time
•The main source of aberrations is the optical components in the system
•Very long integration time
TPF @ Princeton
Problem:
Given an estimate of the wavefront and a
realistic DM model, what should be the
DM’s shape that will create the most optimal
contrast in the image plane?
TPF @ Princeton
Ideal System
TPF @ Princeton
Aberrated System I
TPF @ Princeton
Aberrated System II
beat-down
beat-down
TPF @ Princeton
Aberrated System III
Measured aberration:
Corrected image:
TPF @ Princeton
Suppose we measure the phase aberration up to some maximum spatial frequency:
We may also decompose,
TPF @ Princeton
The components are given by the inner product:
And with a bit of manipulations…
TPF @ Princeton
TPF @ Princeton
10 min later…
where,
TPF @ Princeton
Optimal Correction
The corrected image is given by,
The exponential term could be written as,
TPF @ Princeton
While the cost function minimized in conventional phase conjugation is:
The cost function we are going to minimize now will be:
TPF @ Princeton
Phase aberration
TPF @ Princeton
Point Spread Function
TPF @ Princeton
Conventional phase conjugation
TPF @ Princeton
Point Spread Function )corrected(
TPF @ Princeton
Components )conventional(
TPF @ Princeton
Components )optimal(
TPF @ Princeton
Point Spread Function )corrected(
TPF @ Princeton
Answer:
The shape that will minimize the mean
square sum of the components in the series
for the exponential term.
TPF @ Princeton
Ideal DM
D
D
D
D
abr
meas
DM
null
f
f
f
f
/
/
/
/
100
80
40
40
