We take in consideration three applications which are strongly affected from atmospheric as well as artificial turbulence. Systems in development at the IOSB institute for correcting the turbulence in each application are reported. The set of problems we are interested in are related to the tracking of objects through the atmosphere, the improvement of a laser beam for laser communication or countermeasure and the imaging of objects distorted from turbulent layers. We propose the use of adaptive optics (AO) based on classical Shack-Hartmann sensors (SH) to improve the performances of tracking systems. The SH has the advantage to be sufficiently fast, robust and suited for coherent as well as incoherent point sources correction. In consequence it is also well suited for the purpose of laser beam correction in the atmosphere. The problem of improving a complex image or scene cannot be solved with wavefront sensors in an easy way. A correction of the wavefront based on qua lity metric estimation and the Stochastic Parallel Gradient Descent (SPGD) algorithm is then reported here to cover this aspect. In the final part two modifications of the SPGD algorithm to improve its performances are proposed

Motion-Compensated Averaging (MCA) with blind deconvolution has proven successful in mitigating turbulence effects like image dancing and blurring. In this paper an image quality control according to the "Lucky Imaging" principle is combined with the MCA-procedure, weighting good frames more heavily than bad ones, skipping a given percentage of extremely degraded frames entirely. To account for local isoplanatism, when image dancing will effect local displacements between consecutive frames rather than global shifts only, a locally operating MCA variant with block matching, proposed in earlier work, is employed. In order to reduce loss of detail due to normal averaging, various combinations of temporal mode, median and mean are tested as reference image. The respective restoration results by means of a weighted blind deconvolution algorithm are presented and evaluated

We describe two types of adaptive optics systems developed at FGAN-FOM and the progress in their realization during the last year will be presented. The first system is based on classical adaptive optics scheme and is aimed to resolve objects inside the isoplanatic angle of the wavefront sensor. The second system is based on an iterative algorithm and on the evaluation of the quality of the image to correct the wavefront. This last system is intended to resolve extended targets outside the isoplanatic limits. A constructed mobile system will be also introduced as multipurpose system for measuring atmospheric characteristics as well as tracking and resolving point-like sources in the isoplanatic angle. Finally some results of measurements and attempts to correct the centroid movement of the image of an incoherent point source located at 2.5 km distance using the mobile system will be discussed.

A recently introduced approach to restore images distorted by atmospheric turbulence without a direct knowledge about the wavefront is being discussed in this paper. This technique is based on the use of a deformable mirror controlled by a Stochastic Parallel Gradient Descent (SPGD) algorithm applied to an image quality measurement. This procedure is now being tested for the correction of extended sources as well as laser beams. Because the technique does not rely on wavefront sensors, the problems related to scintillations are noticeably reduced. Preliminary results are presented

Several studies on different adaptive optics concepts are presented in the article. Each one of the procedures shows its peculiar advantages when considering different situations where the image distortion, due to atmospheric or artificial turbulence, becomes problematic. A setup is presented based on the usual wavefront reconstruction techniques using a Shack-Hartmann wavefront sensor in a closed loop with a deformable mirror and a computer. The reconstruction method follows the modal approach which has been demonstrated to be more robust and suitable than the zonal one when limited to the correction of the first Zernike components1 . Some results deriving from the studies are reported. A second part in the article describes the measurements and the characteristics of the atmospheric turbulence present in direct tests. Another procedure based on the control of a deformable mirror by mean of a fast iterative procedure is also treated and the relative results about the c ompensation of laser beams as well as extended images are shown