AIMS太阳望远镜中像旋对稳像精度的影响分析

The Influence of Image Rotation on Accuracy of Stabilization System of AIMS Solar Telescope

针对用于太阳磁场精确测量的中红外观测系统(Accurate Infrared Magnetic field measurements of the Sun,AIMS)太阳望远镜地平式机架在跟踪目标时像场旋转的现象,研究了像场旋转对稳像系统校正精度的影响。首先理论分析了互相关因子算法和绝对差分算法在不同湍流强度及不同探测窗口大小时由像场旋转引起的计算误差。随后在光学分析软件ASAP(Advanced Systems Analysis Program)中建立了包含装配误差的望远镜系统动态光学模型,统计了折轴系统装配误差在望远镜实时跟踪太阳运动时引起的像场平移及旋转。其中,图像在半小时内的最大平移约为0.3 mm,最大像旋约为200″。结果表明,在现有的误差分配情况下,装配误差引起的像旋对稳像精度的影响很小,而为了获得较高的稳像精度,互相关因子算法是首选的稳像算法,且在硬件处理速度允许的情况下,应该选择128×128像素的探测窗口。

Aiming at the phenomenon of image rotation when the coude system of AIMS solar telescope tracks the targets,the influence of image rotation on the correction accuracy of image stabilization system is studied.Firstly,the calculation error caused by the image rotation of the covariance function in Fourier domain and the absolute difference function at different atmospheric turbulence intensity and different detection window sizes is theoretically analyzed.Then,the dynamic optical model of AIMS solar telescope is established in the optical analysis software ASAP.The imaging shift and rotation by the coude system error in the real-time tracking of the sun's motion are calculated.The maximum shift and rotation of the image within half an hour are about 0.3 mm and 200″respectively.The results show that under the existing error distribution situation,the image rotation caused by the assembly error has little effect on the image stabilization accuracy.In addition,in order to obtain higher image stabilization accuracy,the covariance function in Fourier domain is the preferred image stabilization algorithm.And the detection window with 128×128 pixels should be selected as far as the hardware processing speed allows.