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  - Verpoort, Sven
A1  - Bittner, Matthias
A1  - Wittrock, Ulrich
T1  - Fast focus-shifter based on a unimorph deformable mirror
JF  - Applied Optics
N2  - On-the-fly remote laser processing plays an increasingly important role in modern fabrication techniques. These processes require guiding of the focus of a laser beam along the contours of the workpiece in three dimensions.
State-of-the-art galvanometer scanners already provide highly dynamic and precise transverse x−y beam steering. However, longitudinal focus shifting (“z-shifting”) relying on conventional optics is restricted to a bandwidth of a few hundred Hz. We have developed and manufactured a fast piezo-based z-shifting mirror with diffraction-limited surface fidelity providing a focus shift of 1z> 60 mm with an actuation rate of 2 kHz.
KW  - beam steering
KW  - deformable mirrors
KW  - optical components
KW  - laser machining
KW  - laser materials processing
Y1  - 2020
UR  - https://www.osapublishing.org/ao/abstract.cfm?uri=ao-59-23-6959
U6  - http://dx.doi.org/10.1364/AO.397495
SN  - 1559-128X
VL  - 59
IS  - 23
SP  - 6959
EP  - 6965
ER  -