Submitted by Wolfgang GAESSLER
W. Gaessler, D. Peter, C. Storz
MPIA
Phase retrival in the focal plane is a very appealing technique: For conventional AO-systems the limiting magnitude of the system does not depend on the diamter of the telescope, since any wave front sensor splits the light into sub-apertures, which are in number related to the telescope diameter. Having this in mind the phase retrieval technique looks promising as it breaks this paradigm and thus yiels some gain in limiting magnitude with larger telescope diameter. Until now this path was not followed in ASTRONOMICAL Adaptive Optics (AO) systems, as the solution of the inversion is non unique and demands much higher calculation power as in conventional AO. This might change with state of the art computers. We give a short overview of some existing techniques and algorithms of focal plane AO and report also some recent results of other groups, which tested them in laboratory. After that we discuss advantages and disadvantages using such techniqus for ELTs. Finally, we show a possible implementation facilitating some recent development of the MPIA IR detector readout electronic.