The present study utilizes a turbulence radiosonde to obtain profiles of atmospheric temperature, pressure, wind field, and optical turbulence at different time periods in the northwest region of China. Three turbulence parametric models based on Tatarski theory (Dewan model, Kondo model, and HMNSP99 model) are selected for comparison and validation with measured turbulence profiles. According to the radiosonde data, wind shear, potential temperature gradient and Richardson number are calculated, and the corresponding relationship between them and the measured C2n (atmospheric refractive index structure constant) profile is analyzed, which confirms the feasibility of Tatarski theory in the local area. The C2n profiles calculated by the three models were compared with the measured C2n profiles at different time periods. The results show that Tatarski theory has a large error in the estimation of nearsurface layer and boundary layer turbulence, but has a better estimation effect on the free atmosphere turbulence dominated by wind shear. We also analyze the applicability and limitations of the three models, and the results of root mean squared error (RMSE) and correlation coefficient (Rxy) show that the HMNSP99 model has the best application effect in this area, which provides method verification for the application research of atmospheric optical turbulence model in typical region.
This paper illustrates an adaptive mesh grid scaling algorithm, which can be applied in the simulation of laser propagation. The algorithm can effectively improve the far-filed laser spot resolution in the simulation of focused laser propagation. And the algorithm’s effectiveness is verified by the simulation of various laser beam type’s diffraction. The phenomenon of diffraction exits in all the laser beam propagation, in which the divergence angle is directly proportional to the laser wavelength, and inversely proportional to the laser aperture. The proportion coefficients will vary depending on the type of laser beam, such as gaussian beam and flat-topped beam with different obscuration, which have accurately theoretical value. Moreover, the simulation results of adaptive mesh scaling algorithm agree well with theoretical values, which effectively checked the algorithm’s feasibility and accuracy.
Using the sun-sky radiometer CE318 data in 2013~2019 observed in typical dust regions including Kashgar, Zhangye and Minqin, the variation characteristics of Aerosol Optical Depth(AOD), Angstrom exponent, single scattering albedo and asymmetry factor were analyzed. The results show as follows. There are significant differences in the variability characteristics of AOD at three typical dust-type stations. The seasonal variation of AOD in Kashgar is the most obvious. The highest AOD is in spring with more dispersed KDE, and the lowest in winter with more concentrated KDE. In Zhangye and Minqin, the seasonal difference of AOD is small, with monthly means below 0.9 and more concentrated distribution in the range of 0.5~0.8. The value of Angstrom exponent in Kashgar is higher in autumn and winter than spring and summer. In spring, summer and autumn, Zhangye and Minqin have significantly higher Angstrom exponent than Kashgar. The single scattering albedo in all three stations is above 0.85, and the asymmetry factor ranges from 0.63~0.8, indicating that the aerosol scattering effects are evident throughout the year.
High power fiber lasers can be incoherently combined to form the basis for high energy laser applications. Incoherent combining of fiber lasers has a number of advantages over other laser beam combining methods. However, the far-field beam quality of the incoherently combined laser array can still be significantly degraded by atmospheric optical turbulence. In this article, a general scaling law for propagation of incoherently combined laser array through atmosphere is developed by employing theoretical analysis and the common stochastic wave optics technique, and mainly focus on the effects of diffraction and atmospheric optical turbulence. The scaling law developed in the present work differs from standard scaling laws in its definition of irradiance. We show that the far-field irradiance and beam dispersion of any incoherently combined laser array, regardless of near-field beamlets geometry, can be obtained in terms of four basic parameters: laser power, field effective area, pupil field factor, and the Fried parameter.The results show that the formula is simple but predicts peak irradiance and beam dispersion accurately in the far field with varying levels of atmospheric turbulence, regardless of the near-field beamlets geometry.
Pointing precision of attitude stabilization platform is important for airship during its flight and it is one of the key factors to make sure that the antenna isolates disturbance from airship and tracks target with stable attitude. Therefore, in this paper, a method of real-timely measuring pointing precision of attitude stabilization platform based on image processing is established to test attitude stabilization platform performance. In addition, a method of real-time extraction for target with Harris algorithm based on local Otsu threshold segmentation is established for real-time automatic measurement. This method overcomes the problems of long shooting distance, small imaging area of target and the bad light. The experimental results show our method can real-time measure the pointing precision for attitude stabilization platform and the measured value fits well with the design value .
In range test, for measuring the target attitude in target terminal trajectory, we developed a fast Hough transform to real-timely extract axes of the axes symmetry target in high-speed image processing system. The theoretical analysis shows that the accuracy of this scheme is higher than that of standard Hough transform, and the closer to one the absolute value of slope is, the lower the error is. Experimental result shows that the computing speed for line detection of this scheme is higher than standard Hough transform, and the greater the noise is, the more obvious the advantage of speed is. In addition, the error distribution of the experiment is in agreement with the theoretical error distribution.
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