The effectiveness of reconstruction of images formed by single- and multi-aperture systems and disturbed by atmospheric turbulence is analyzed. Based on the numerical simulation, we show that the use of multi-aperture observation systems for the computer correction of atmospheric disturbances under anisoplanatism allows a significant reduction of the exposure time. Main distortions are well corrected in this case during imaging for the short exposure time, which corresponds to the “frozen” turbulence of the medium. The time required for the correction of residual small-scale disturbances is an-order-of-magnitude shorter than in the case where long-exposure images are synthesized with traditional single-aperture observation systems.
The influence of the receiving aperture size and photo detector array resolution on the accuracy of crosswind speed estimation from the correlation analysis of turbulent distortions in optical images is studied in numerical simulation. Receiving optical system (video camera) parameters optimal for the technique for passive estimation of crosswind speed are determined.
Possibilities a passive method developed for estimation of the crosswind velocity from a video sequence of incoherent images along 1 km observation paths are analyzed. The method results are compared with anemometer measurements.
In this paper an analysis of the atmospheric model represented as a homogeneous surface layer and another homogeneous layer 10 km is provided. Parameters of the layers are defined for the standard atmosphere, provided that the contribution of the outgoing radiation atmosphere in the studied spectral plots methane absorption lines 1240.980 -1241.020 cm-1, 1240.901 -1240.949 cm-1 equal to deposits in the outgoing radiation from the Earth all mixed layers and their components. A system of two equations is solved, relating their content in each of the homogeneous layers with a change in the power of the outgoing radiation for each spectral region.
Possibilities of enhancing the operational efficiency of optical multiaperture systems in a turbulent atmosphere were studied through numerical simulation. Features of synthesizing an object image as a sum (superposition) of images from every individual aperture were analyzed in the presence of turbulent distortions. The quality of images synthesized by an array of N×N subapertures (N=5–15) was examined. It is shown that turbulent distortions in an image synthesized by many subapertures with allowance made for shifts of subimages at every subaperture are isoplanatic in a wide range of atmospheric conditions. This allows significant improvement of the image quality by means of computer correction. In this case, there is an optimal subaperture size mainly determined by the Fried parameter, which characterizes the degree of turbulent distortions.
We suggest a method for filtration of incoherent optical images of objects in the atmosphere, which allows one to observe cross shifts of turbulent air inhomogeneities at the observation path. It is shown that the characteristic size of anisoplanatic distortions in images observed through the atmosphere is mainly determined by the distance to the layer of turbulent inhomogeneities that cause these distortions. An algorithm is suggested for the filtration of turbulent distortions by their characteristic size in order to mark out the effect of turbulent medium layers specified. The capabilities of the algorithm for cross wind retrieval from the analysis of a video sequence of short-exposure images at surface horizontal paths are shown. The main advantage of the suggested method for cross wind retrieval from the analysis of two neighbor frames of video sequence is its high speed since there is no need to accumulate statistics of the analyzed parameters. The retrieved wind speed is compared with data of acoustic anemometers located along an observation path 500 m long. The good accuracy of retrieval of the cross wind at path segments close to an observer, as well as of the average wind speed over the entire observation path, is demonstrated.
Possibilities of determining optimal conditions for laser beam focusing in a turbulent atmosphere on the basis of the analysis of target image distortions are analyzed. A series of metrics is considered, which characterize the efficiency of laser beam focusing and the target image quality. A correlation is found between metric fluctuations in the target and observation planes in a dynamically varying turbulent atmosphere in the case of aligned optical axes of the beam focusing and observing systems. As applied to wireless communications, it is shown from the analysis of object images (radiation detector) that the adaptive control of tilts of optical axis of only the transmitting laser system significantly increases the efficiency of data communications.
Possibilities of the wind speed profiling along an observation path of a distant object from the analysis of a video sequence of images of the object are studied in this work by numerical simulation. The method is based on the analysis of two neighbor frames of a video sequence of incoherent images. It is more rapid than analogous methods, due to the absence of need in accumulation of the statistics of parameters analyzed. It is shown that the drift speed of several (no less than 3) turbulent layers, located at different distances between the object observed and the receiving optical system, can be determined for some turbulent conditions and object parameters. The method accuracy is estimated for wide ranges of atmospheric conditions and parameters of the object observed.
Possibilities of retrieval of the drift velocity of atmospheric turbulence inhomogeneities from a video sequence of incoherent images of an object are studied numerically in the work. A method for filtration of turbulent distortions of an image by their characteristic sizes is suggested with the aim to determine the wind speed at different segments of an observation path. The method testing for the cases of two layers of turbulent inhomogeneities that drift in different (mutually normal) directions has shown high accuracy of retrieval of their drift velocities.
An effect of turbulent inhomogeneities, differently distant from an observer, on distortions of atmospheric object images is analyzed on the basis of numerical simulation. A technique for determining the atmospheric inhomogeneity wind drift from sequence of images of an object specified is suggested. A capability of the technique of determining the atmospheric inhomogeneity wind drift from two images is shown.
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