Static telescope aberration measurement and correction using lucky imaging techniques
Static telescope aberration measurement and correction using lucky imaging techniques
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使用幸运成像技术进行静态望远镜像差测量和校正
DOI：
10.1117/12.787413
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发表时间：
2008
期刊：
影响因子：
--
通讯作者：
J. M. Ramos
中科院分区：
文献类型：
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作者：
M. L. Marrero;L. F. R. Ramos;J. M. Ramos
摘要利用近邻恒星作为点源探测光学系统，发展了一种用瑞幸成像技术测量PSF后计算静态像差的方法。利用Gerchberg-Saxton算法将这种PSF在光瞳处按比例转换成相位图，然后转换成足够的驱动信息，以满足驱动器数量少但行程能力大的可变形反射镜的需要。这种方法的主要优点是能够在特定的指向方向上校正静态像差，而不需要波前传感器。关键词：静态像差，幸运成像，位相恢复L，格希伯格-萨克斯顿，衍射极限成像。1.导言当今大多数望远镜的设计都是考虑到统计数据是静态像差误差预算的参考。实验表明，望远镜镜片支承的挠度在指向天空的不同方向时不会引起明显的像差，与平均目视图形相比不会引起明显的像差。像幸运成像(FastCam)[1][2]这样的新观测技术已经证明了它们有能力在I波段、在1到4米的望远镜上常规提供衍射限制成像，甚至能够在Observatorio del Teide(Tenerife，Canary is)1.5米的TCS获得艾利环。西班牙)。一旦消除了大气湍流，只要主镜的形状在可行的情况下得到了充分的调整，镜面未对准造成的剩余像差就是空间分辨率的限制因素。这种像差取决于指向方向，主要是由于重力对机械结构的影响。用近星作点源探测光学系统，用瑞幸成像技术测得点扩展函数(PSF)后，建立了计算静态误差比的程序。利用Gerchberg-Saxton算法[3]，将这种PSF迭代地转换为光瞳处的相位映射，并在将来转换为足够的驱动信息，以用于驱动器数量少但行程能力大的可变形镜。由于该算法是一个很好的开发和调试平台，可以方便地测试其性能，因此使用了MatLab来开发和测试该算法，但该项目的未来目标是使用现场可编程门阵列(现场可编程门阵列)来实时执行该算法，同时利用这种方法的所有优点。这种方法的主要优点是能够在特定的指向方向上校正静态像差，而不需要波前传感器。本文描述了在OBS的1.5TCS上完成的PSF测量和相位恢复。电话：+34 922 605 200；传真：+34 922 605 210；www.iac.es
ABSTRACT A procedure has been developed to compute static aberrations after the PSF measured with the lucky imaging technique, using a nearby star as the point source to probe the optical system. This PSF is ite ratively turned into a phase map at the pupil using the Gerchberg-Saxton algorithm, and then conver ted to the adequate actuation information for a deformable mirror having low actuator number but large stroke capability. The main advantage of this procedure is related with the ca pability of correcting static aberration at the specific pointing direction and without the need of a wavefront sensor. Keywords: Static aberrations, lucky imaging, phase retrieva l, Gerchberg-Saxton, diffraction limit imaging. 1. INTRODUCTION Most present-day telescopes were designed bearing in mind th e seeing statistics as the refere nce for the error budget in static aberrations. It was expe cted for the telescope mirror supports flexures not to introduce significant aberration when pointing to the different directions on sky, in comparison with mean seeing figures. New observing techniques like Lucky Imaging (FastCam)[1][2] have demonstrated their capability to routinely provide diffraction limited imaging in the I-Band, at telescopes in the range 1to 4 meters, and even to obtain Airy rings at the 1.5 meter TCS at Observatorio del Teide (Tenerife, Canary Is. SPAIN). Once the atmospheric turbulence is removed, a remaining aberration due to mirror misalignment is the limiting factor in spatial resolution, provided the shape of the primary mirror has been adequately adjusted whenever feasible. This aberration depends on the pointing direction, mostly due to the effect of grav ity on the mechanical structure. A procedure has been developed to compute these static aber rations after the Point Spread Function (PSF) measured with the lucky imaging technique, using a near by star as the point source to probe th e optical system. This PSF is iteratively turned into a phase map at the pupil using the Gerchberg-Saxton algorithm[3], and will be converted in the future to the adequate actuation information for a deformable mirror ha ving low actuator number but large stroke capability. This algorithm has been developed and testd using MATLAB, since it is a nice development and debugging platform and to tests its capabilities easily, but the future aim of the project is to use FPGAs (Field Programmable Gate Array) to execute the algorithm in real time, w ith all the advantages this means. The main advantage of this procedure is related with the ca pability of correcting static aberration at the specific pointing direction and without the need of a wavefront sensor. This paper describes the PSF measuring and phase recovery that have been accomplished and tested at th e 1.5 TCS at Obs. del Teide (Canary Is.) *LRR@iac.es; phone +34 922 605 200; fax +34 922 605 210; www.iac.es