The results of full-scale experiments in the atmosphere with various turbulence state meters are considered. In measurements on horizontal open atmospheric paths of various lengths, three optical meters and an acoustic weather station were used. Based on the test results of the meters, a high correlation of turbulence measurements made by optical differential meters DIT-2 and DIT-M as well as the AMK-03 ultrasonic acoustic weather station was shown. Conclusions are drawn about the accuracy and applicability of the meters used to assess the level of turbulence along the atmospheric paths.
A description of the stand for an adaptive optics system operating in the mode of emulation of the slopes of the laser radiation wavefront on a turbulent path is given. The potential capabilities of the test bench involve setting the parameters of turbulent distortions characteristic of paths of various lengths, as well as using a piezceramic deflector of wavefront slopes as a source of emulated image distortions in the observation plane. The stand of the adaptive optics system makes it possible to stabilize the jitter of the optical radiation image in the plane of the receiving device with the adaptive correction circuit turned on and off under conditions of various system operation modes.
Under the influence of atmospheric turbulence and as a result of natural vibrations of the adaptive optics system, the radiation images in the focal plane fluctuate in time relative to the laser radiation propagation axis, leading to a change in the wave front tilt angles. When accurate positioning of the focal spot is required, the elimination of angular errors becomes an important point in astronomical observations. Image stabilization on the photo detector matrix of the optical system is performed by the tilt corrector, which is one of the key elements of the software and hardware complex for emulating the tilt of the wave front.
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 [1] 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.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.