大口径空间巡天望远镜子孔径拼接平场定标法

Flat-field calibration method for large diameter survey mirror aperture splicing

大口径空间巡天望远镜的精确平场定标是实现既定科学目标的重要前提。目前普遍是通过平场屏幕或大口径积分球提供均匀平场基准来检验像面响应一致性。针对平场屏幕照明均匀性差,超大口径积分球制备困难等问题,本文提出了一种基于子孔径扫描的平场定标方法,以改善平场基准的均匀性及杂散光导致的定标不确定度。首先,完成子孔径平场定标理论分析,建立子孔径平场定标数学模型,规划子孔径扫描路线及扫描孔径大小,进行标定用准直系统参数的初设计。其次,完成像面照度仿真验证实验。最后,搭建实验平台,对规划的子孔径进行扫描,构建全口径照度数据,验证上述大口径空间巡天望远镜子孔径拼接平场定标方案的可行性。实验结果表明:以全口径为基准,用子孔径拼接法扫描待测系统像面能量叠加对比全口径像面照度,能够恢复全口径的照度信息,全口径像面灰度值为231.085,单个子孔径叠加灰度值为233.350,误差为1%,本文研究表明子孔径拼接法可用于大口径巡天望远镜的平场定标,具有实际应用价值。

The accurate flat-field calibration of large-diameter space survey telescopes is an important prerequisite for achieving some established scientific goals.At present,it is common practice to provide a uniform flat-field reference through a flat-field screen or a large-diameter integrating sphere,which is used to check the consistency of an image’s plane response.To address issues with the uniformity of flat-field screen illumination and the difficulty of preparing large-size integrating spheres,a flat-field calibration method based on sub-aperture scanning is proposed in this paper,which improves the uniformity of the flat-field reference and the uncertain calibration caused by stray light.First,we complete a sub-aperture flat-field calibration theory analysis,establish a sub-aperture flat-field calibration mathematical model,plan the sub-aperture scanning route and scan aperture size,and perform the initial design of the parameters of the collimation system for calibration.Secondly,we complete the image surface illumination simulation verification experiment.Finally,we set up an experiment to scan the planned sub-apertures,build full-aperture illuminance data,and verify the feasibility of the above-mentioned large-aperture space survey telescope sub-aperture stitching flatfield calibration scheme.The experimental results show that the full-aperture illuminance information can be restored using the full-aperture stitching method to scan the image surface energy of the system and by using the sub-aperture stitching method to compare and contrast the full-aperture image surface illuminance.The superimposed gray value in our experiment was 233.350 and the error was 1%.It is therefore verified that the sub-aperture stitching method can be used for flat-field calibration of large-diameter sky survey telescopes,and has practical value in real-world applications.