TY  - CHAP
A1  - Kazasidis, Orestis
A1  - Verpoort, Sven
A1  - Wittrock, Ulrich
T1  - Image-based wavefront correction for space telescopes
T2  - International Conference on Space Optics - ICSO 2018
N2  - With a view to future large space telescopes, we investigate image-based wavefront correction with active optics. We use an image-sharpness metric as merit function to evaluate the image quality, and the Zernike modes as control variables. In severely aberrated systems, the Zernike modes are not orthogonal to each other with respect to this merit function. Using wavefront maps, the PSF, and the MTF, we discuss the physical causes for the non-orthogonality of the Zernike modes with respect to the merit function. We show that for combinations of Zernike modes with the same azimuthal order, a flatter wavefront in the central region of the aperture is more important than the RMS wavefront error across the full aperture for achieving a better merit function. The non-orthogonality of the Zernike modes with respect to the merit function should be taken into account when designing the algorithm for image-based wavefront correction, because it may slow down the process or lead to premature convergence.
KW  - active optics, adaptive optics, sharpness metrics, aberration compensation, algorithm design
Y1  - 2019
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:hbz:836-opus-109036
UR  - https://www.spiedigitallibrary.org/conference-proceedings-of-spie/11180/111807Z/Image-based-wavefront-correction-for-space-telescopes/10.1117/12.2536206.full?SSO=1
SP  - 111807Z
PB  - Proc. SPIE
ER  - 
TY  - JOUR
A1  - Kazasidis, Orestis
A1  - Verpoort, Sven
A1  - Wittrock, Ulrich
T1  - Aberration balancing using an image-sharpness metric
JF  - J. Opt. Soc. Am. A
N2  - Image-sharpness metrics can be used to optimize optical systems and to control wavefront sensorless adaptive optics systems. We show that for an aberrated system, the numerical value of an image-sharpness metric can be improved by adding specific aberrations. The optimum amplitudes of the additional aberrations depend on the power spectral density of the spatial frequencies of the object.
KW  - adaptive optics; image-sharpness
Y1  - 2019
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:hbz:836-opus-109198
UR  - https://www.osapublishing.org/josaa/abstract.cfm?uri=josaa-36-8-1418
VL  - 36
IS  - 8
SP  - 1418
EP  - 1422
ER  -