The temporal error of the adaptive optical system leads to a significant degradations in the characteristics of the system operating in the atmosphere. One of the methods for solving this problem is the use of prediction algorithms based on the analysis of the evolution of phase fluctuations. In the paper the wavefront sensor as the key element of atmospheric adaptive optical system with predictions algorithms is considered. The results of the development and testing of the Shack-Hartmann wavefront sensor providing measurements of phase fluctuations, determination of the Fried parameter and wind speed using original design solutions and software are presented. The practical and theoretical aspects of using the Shack-Harmann wavefront sensor are discussed. For it dynamic range, sensitivity and accuracy of the sensor are estimated. The influences of parameters of microlens array on range of measurements of the Shack-Harmann wavefront sensor are studied. The tests of the S-H WFS were carry out with acoustic measurements of wind speed and the structural constant of the refractive index of the atmosphere, as well as in adaptive optics system in laboratory test bench.
We describes the status of AO test bench, which is developing at the Adaptive optics Lab, V.E. Zuev Institute of Atmospheric Optics of the Siberian Branch of the Russian Academy of Sciences (IAO SB RAS), Tomsk, Russia to simulate predictive algorithms of wavefront adaptive correction. The description of the optical and mechanical design, components AO bench, and the working principle and first experimental results are presented. The current AO test bench consists of laser source, two deformable mirrors with 59 actuators and 56 mm diameter (Visionica Ltd., Russia), two tip/tilt mirrors (IAO SB RAS, Russia), Shack-Hartmann Wavefront Sensor (WFS), which we specially designed, and a science camera for the evaluation of the performance. The user derived aberrations are introduced using a one deformable mirror and corrected by another deformable mirror. The tip/tilt mirrors are used for predictive control of the low-order wavefront aberrations related such as vibrations.
The possibilities of forming optical images on horizontal extended atmospheric paths are explored. Two different methods for improving image quality are analyzed. It is known that at the present time the solution of the problem of long-range vision with super-high resolution is conducted along several independent lines, firstly, on the development of methods based on the classical technique of adaptive optics, i.e., by correcting the distorted wavefront itself, and, secondly, on the use of digital post-detection techniques, as well as, on the way to attract purely engineering solutions. These methods are applied, both for terrestrial systems, and for astronomical instruments. They can be instrumental (for example, adaptive correction, the use of polarization filters, receiver gating, etc.), mixed (adaptive correction and subsequent processing of images on computers or special processors) or program-algorithmic only. The analysis is carried out for systems operating on horizontal paths. This, first of all, is due to the fact that any horizontal path by the strength of turbulence far exceeds any astronomical one. On extended horizontal paths, in addition to phase distortions that cause the effects of jitter and blurring of the image, there are fluctuations in the intensity of the received radiation, which leads to the appearance of flickering effects of the image, as well as to the manifestation of ambiguity in describing the phase distortions of the optical wave. Numerical and analytical calculations are performed. Experiments were carried out on the atmospheric paths from 160 m to 3.2 km long in city conditions.
According to the work plan for the RSF project, during 2016 measurements were taken in all seasons of the year: February, April, May, August and October. With the use of the whole set of equipment of the stand on the BSVT, the task was set to work out methods for recording and correcting the distortions of the phase of optical radiation passing through a layer of turbulent atmosphere. Complex on-site meteorological observations were organized and conducted at the site of the BSVT. Observations were carried out with the aim of developing and improving the local computational model of turbulent characteristics in the entire thickness of the active atmosphere in the "optical turbulence" range, including the surface layer. As the initial meteorological information for calculations, the model uses two-level data of pulsating observations of temperature and wind speed at the BSVT site, as well as current NCEP/NCAR archival data for the period from 1948 to 2015.
The results of optical measurements of the quality of astronomical seeing on the Large solar vacuum telescope (LSVT) in spring and summer are shown. It is noticed that in the summer measurements, the quality of vision is higher on average 2.5 times than in the spring. Information on the seasonal variability of the astronomical quality of vision can be useful in the planning of scientific experiments for the LSVT, as well as to improve the performance of existing adaptive system