A multi-cascade adaptive optical system for imaging and image stabilization for the Large Solar Vacuum Telescope is described. This system was created in 2017 by specialists of the V.E. Zuev Institute of Atmospheric Optics SB RAS, Tomsk, with the technical support of the Institute of Solar-Terrestrial Physics SB RAS, Irkutsk. The system has been tested at the Large Solar Vacuum Telescope (Baikal Astrophysical Observatory) and demonstrated its efficiency. Along with the first cascade of adaptive image stabilization by a tip-tilt corrected mirror, this system employs the second imaging cascade based on correction with a flexible mirror controlled by a specialized wavefront sensor, as well as the third cascade for real-time post-detector processing of video camera frames. Reliable experimental data confirming the efficiency of the multi-cascade adaptive system for image formation and stabilization have been obtained. Three highrate digital video cameras recording simultaneously digital images with rates from 300 to 980 frames per second were used to test the system. The mirror correcting wavefront tilts and operating in a closed optical feedback loop was controlled by the specially developed software including the fast correlation tracking algorithm. The post-detector digital imaging was performed with a special software for processing of video camera frames in real time with the use of modern high-speed parallel algorithms based on the Intel MKL and IPP libraries.
A new model of an optical deflector is proposed for controlling the tilt angles of optical radiation in adaptive optical systems and stabilizing its image at the input aperture. The deflector contains an electronic control unit that works with digital and analog input signals, and an actuator consisting of piezoceramic actuators and a flat mirror. Unique design solutions of the actuator ensure the preservation of flatness of the mirror over the entire range of tilt angles, and the electronic damping system suppresses the vibration of the mirror with a pulse control signal. The adaptive optics system with the presented deflector can be applied in astronomical telescopes, in ground-based vision systems on turbulent atmospheric paths, and in laser sounding problems.
It are evaluated characteristics of an simulation stand on adaptive optics. The stand is created on the basis of LCAO IOA SB RAS in order to work out algorithms for adaptive correction, research and testing of measuring equipment. The stand allows generating turbulence with given parameters for a particular flexible mirror. In this case, a wave front with different turbulent inhomogeneities with varying their intensity is formed, and the wind transfer of inhomogeneities in the plane of the entrance aperture of the system is also set. For the deflector  included in the stand scheme, the tilt angles of the optical radiation are programmed. The Shack-Hartman wavefront sensor and, in parallel with it, a split photodetector measure the characteristics of the incoming optical radiation, which are compared with given parameters. The flexible mirror and deflector reproduce turbulence with given parameters and slopes, respectively.
An optical deflector designed to stabilize the position of the image at the input aperture of the optical system has been developed. The deflector contains an electronic control unit that operates with digital and analog input signals and an actuator based on piezoceramic actuators and a flat mirror. Special design solutions of the actuator ensure that the flatness of the mirror remains in the entire range of correction angles, and the electronic damping system suppresses the vibration of the mirror under a pulsed control signal. Adaptive optics systems with the described deflector are applicable in astronomical telescopes, in ground-based video surveillance and laser scanning systems.
To calculate the control signals of a piezoceramic deflector when measuring the angles of arrival of optical radiation transmitted through atmospheric turbulence, various methods for estimating the beam image in the focal plane of the recording device can be used. The results of numerical studies of the accuracy of calculating the energy center of gravity of an image in the focal plane in several different ways are presented. These methods are used both in split photodetectors and in the Shaсk-Hartmann wavefront sensors.
To stabilize the image on the input aperture of the adaptive optics system, a model of the control device for the general angle of inclination of the wavefront is created. The device designed to eliminate image jitter due to atmospheric turbulence and the vibrations of the telescope itself makes it possible to control both the overall wavefront slopes at the input aperture of the system and the wavefront shift along the propagation axis of the beam. For testing the device, a program has been developed that simulates the angles of the wavefront inclination during the formation of an optical beam whose position at the input aperture of the adaptive system is unstable under the influence of atmospheric turbulence.