TY - JOUR A1 - Kazasidis, Orestis A1 - Verpoort, Sven A1 - Soloviev, Oleg A1 - Vdovin, Gleb A1 - Verhaegen, Michel A1 - Wittrock, Ulrich T1 - Extended-image-based correction of aberrations using a deformable mirror with hysteresis JF - Opt. Expr. N2 - With a view to the next generation of large space telescopes, we investigate guide-star-free, image-based aberration correction using a unimorph deformable mirror in a plane conjugate to the primary mirror. We designed and built a high-resolution imaging testbed to evaluate control algorithms. In this paper we use an algorithm based on the heuristic hill climbing technique and compare the correction in three different domains, namely the voltage domain, the domain of the Zernike modes, and the domain of the singular modes of the deformable mirror. Through our systematic experimental study, we found that successive control in two domains effectively counteracts uncompensated hysteresis of the deformable mirror. KW - active optics, metrics, aberration compensation Y1 - 2018 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:hbz:836-opus-14759 UR - https://www.osapublishing.org/oe/fulltext.cfm?uri=oe-26-21-27161&id=398820 VL - 26 SP - 27161 EP - 27178 ER - TY - CHAP A1 - Kazasidis, Orestis A1 - Verpoort, Sven A1 - Wittrock, Ulrich T1 - Algorithm design for image-based wavefront control without wavefront sensing T2 - SPIE Optical Instrument Science, Technology, and Applications, Proc. SPIE N2 - Active optics is an enabling technology for future large space telescopes. Image-based wavefront control uses an image-sharpness metric to evaluate the optical performance. A control algorithm iteratively adapts a corrective element to maximize this metric, without reconstructing the wavefront. We numerically study a sharpness metric in the space of Zernike modes, and reveal that for large aberrations the Zernike modes are not orthogonal with respect to this metric. The findings are experimentally verified by using a unimorph deformable mirror as corrective element. We discuss the implications for the correction process and the design of control algorithms. KW - active optics, adaptive optics, sharpness metrics, aberration compensation, algorithm design Y1 - 2018 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:hbz:836-opus-14760 UR - https://www.spiedigitallibrary.org/conference-proceedings-of-spie/10695/1069502/Algorithm-design-for-image-based-wavefront-control-without-wavefront-sensing/10.1117/12.2312523.full VL - 10695 SP - 1069502 ER - TY - BOOK ED - Wittrock, Ulrich T1 - Adaptive optics for industry and medicine. Proceedings of the 4th International Workshop on Adaptive Optics for Industry and Medicine Y1 - 2005 UR - https://www.springer.com/de/book/9783540239789 SN - 3-540-23978-2 PB - Springer CY - Berlin ER - TY - JOUR A1 - Wittrock, Ulrich T1 - Laryngeally echolocating bats (Brief Communication Arising) JF - Nature Y1 - 2010 U6 - http://dx.doi.org/10.1038/nature09156 VL - 466 SP - E6 ER - TY - CHAP A1 - Verpoort, Sven A1 - Wittrock, Ulrich T1 - Miniaturized adaptive mirror for solid state laser resonators T2 - Proceedings of the 7th International Workshop on Adaptive Optics for Industry and Medicine, Shatura, Russia Y1 - 2009 ER - TY - JOUR ED - Wittrock, Ulrich ED - Kynast, Ulrich ED - Jüstel, Thomas ED - Bredol, Michael T1 - 6th Laser Ceramics Symposium T2 - Opt. Mat. Y1 - 2012 UR - https://www.sciencedirect.com/journal/optical-materials/vol/34/issue/6 VL - 34 SP - 935 EP - 1002 PB - Elsevier B.V. ER - TY - JOUR A1 - Wittrock, Ulrich T1 - Grenzen? Welche Grenzen? Prof. Ulrich Wittrock, Leiter des Labors für Photonik an der Fachhochschule Münster, fragt nach den ultimativen Grenzen der Lasertechnik JF - Laser Community - das Lasermagazin von Trumpf Y1 - 2014 VL - 02:14 ER - TY - JOUR A1 - Wittrock, Ulrich T1 - Limitations? What Limitations? Prof. Ulrich Wittrock, head of the Photonics Laboratory at the Münster University of Applied Sciences, seeks out the ultimate boundaries of laser technology JF - Laser Community - the laser magazine from Trumpf Y1 - 2014 VL - 02:14 ER - TY - CHAP A1 - Verpoort, Sven A1 - Wittrock, Ulrich T1 - Deformable mirrors for high power lasers T2 - Proceedings of the 8th International Workshop on Adaptive Optics for Industry and Medicine (AOIM) N2 - It has been shown that the beam quality and the efficiency of high-power solid-state lasers could be enhanced by the use of deformable mirrors in order to compensate for optical aberrations. An intracavity compensation requires a deformable mirror which is capable of handling very high laser intensities. The active diameter of the deformable mirror should be a few millimeters in order to match typical fundamental mode laser beam diameters. There is a wide variety of commercially available deformable mirrors, but neither meets all requirements. KW - Deformable mirror, adaptive mirror, unimorph mirror, high-power laser Y1 - 2011 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:hbz:836-opus-106953 UR - http://congresos.um.es/aoim/aoim2011/schedConf/presentations ER - 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 -