Panahi M, Shomali R, Mollabashi M
J Opt Soc Am A Opt Image Sci Vis. 2019 Apr 1;36(4):655-664. doi: 10.1364/JOSAA.36.000655.
We report on an analytic method to estimate the Fried parameter r, average wind speed v¯, and subsequently the atmospheric coherence time τ via a 4-aperture differential image motion monitor (DIMM) instrument. The theory developed here shows that the velocity of defocus aberration is statistically related to atmospheric turbulence parameters which are measured by means of angle of arrival (AA) fluctuations. Then, using the variance of the defocus velocity of four spots and the derived analytic relation, the atmospheric coherence time can be estimated. In parallel to the analytic work, some sequences of a star image with 700 Hz acquisition frequency are considered to simulate the atmospheric defocus and its variations by the 4-aperture DIMM instrument for the first 10 km near the ground in both one- and three-layer atmospheric models. The estimations from the analytic method are found to be in good agreement with the simulation data obtained for starlight propagating through different atmospheric conditions.
我们报告了一种通过四孔径差分图像运动监测仪（DIMM）来估计弗里德参数r、平均风速v¯以及随后的大气相干时间τ的分析方法。这里所发展的理论表明，离焦像差的速度与通过到达角（AA）波动测量的大气湍流参数存在统计关联。然后，利用四个光斑离焦速度的方差以及推导得到的解析关系，就可以估计大气相干时间。在进行分析工作的同时，考虑了一些采集频率为700Hz的恒星图像序列，以通过四孔径DIMM仪器在单层和三层大气模型中模拟近地面10公里范围内的大气离焦及其变化。结果发现，分析方法的估计值与通过不同大气条件下传播的星光获得的模拟数据高度吻合。
