用于开环液晶自适应光学系统的模式预测技术研究
- 中国科学院长春光学精密机械与物理研究所应用光学国家重点实验室,长春130033 中国科学院研究生院,北京100049
- 中国科学院长春光学精密机械与物理研究所应用光学国家重点实验室,长春,130033
- 大连民族学院光电子技术研究所,大连,116600
摘要: 时间延迟误差是液晶自适应光学系统的一个最主要的误差源．本文提出了一种利用智能模式预测一迭代最小二乘（RLS）模式预测算法来克服其对成像分辨率的影响．首先，介绍了具有RLS模式预测能力的开环液晶自适应光学系统的结构和工作原理．其次，详细讨论了RLS模式预测算法的实现过程．再次，设计和搭建了一套带有液晶湍流模拟器的开环液晶自适应光学系统，对RLS模式预测算法的预测效果进行了分析，并和直接开环校正做了比较．分析结果表明：当系统处于中等强度湍流条件（大气相干长度r0=6cm，Greenwood频率fG=35Hz）和只有时间延迟误差情况下，经过RLS预测后，残差波面的RMS值由直接校正的0．26波长（1波长=785nm）降低到了0．15波长，校正效果提高了42％．最后，对预测前后自适应光学系统的成像效果进行了对比试验．实验结果显示，经过预测以后，系统的成像分辨率由直接开环校正的25．4cycles／mm提高到了32．0cycles／mm，成像分辨率提高了26％，达到了0．9倍的衍射极限分辨率．因此，RLS模式预测技术可以有效的提高开环液晶自适应系统的成像分辨率．
Modal prediction for open-loop liquid-crysta adaptive optics systems
- 中国科学院长春光学精密机械与物理研究所应用光学国家重点实验室,长春130033 中国科学院研究生院,北京100049
- 中国科学院长春光学精密机械与物理研究所应用光学国家重点实验室,长春,130033
- 大连民族学院光电子技术研究所,大连,116600
Abstract: In order to reduce the time delay of the liquid-crystal （LC） adaptive optics system （AOS） which reduces the image resolution of the observed objects, we present a new technique for the first time which is called recursive least square （RLS） modal prediction of turbulent wavefront. First, we introduce the structure of the open-loop LC AOS with RLS predictor. Second, we present the RLS modal prediction algorithm in detail. Third, an actual open-loop LC AOS is designed and built, and the RLS prediction is carried out on it. It is shown that under a pure time delay system and the turbulent condition with Greenwood frequency of 35 Hz and Fried parameter of 6 cm, after prediction the residual wavefront error reducs to 0.15 wave （wave -- 785 nm） from 0.26 wave that is obtained through the direct open loop correction. The prediction gain reaches 42%. Finally, the images obtained by the open-loop AOS with and without prediction are demonstrated. With direct correction without prediction, the image resolution reache 25.4 cycles/ram. After the correction with RLS prediction, the image resolution reaches 32.0 cycles/mm which is equal to 0.9 of the diffraction limit resolution of the system. Therefore, with respect to correction without prediction, a relative gain of 26% in image resolution is achieved with RLS prediction. In conclusion, the RLS modal prediction can improve the image resolution of the open-loop LC AOS effectively.
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