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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=6 cm, Greenwood频率fG=35 Hz)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=785 nm)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25.4 cycles/mm提高到了32.0 cycles/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.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 35Hz and Fried parameter of 6 cm, after prediction the residual wavefront error reduce 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/mm. 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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Keywords:
- adaptive optics /
- turbulent prediction /
- recursive least square /
- liquid crystal wavefront corrector
[1] Love G D 1997 Appl. Opt. 36 1517
[2] Prieto P, Fernandez E, Manzanera S, Artal P 2004 Opt. Express 12 4059
[3] Schmidt J, Goda M, Duncan B 2007 Appl. Opt. 46 2423
[4] Cai D M, Ning N, Jiang W H 2008 Acta Phys. Sin. 57 897 (in Chinese) [蔡冬梅, 凌宁, 姜文汉 2008 57 897]
[5] Li C, Xia M, Mu Q, Jiang B, Xuan L, Cao Z 2009 Opt. Express 17 10774
[6] Liu C, Hu L, Mu Q, Cao Z, Xuan L 2011 Appl. Opt. 50 82
[7] Mu Q, Cao Z, Peng Z, Liu Y, Hu L, Lu X, Xuan L 2010 Opt. Commun. 283 2017
[8] Mu Q, Cao Z, Li D, Hu L, Xuan L 2008 Appl. Opt. 47 4279
[9] Li C, Xia M, Li D, Mu Q, Xuan L 2010 J. Biomed. Opt. 15 046009-1
[10] Jiang B G, Cao Z L, Mu Q Q, Li C, Xia M L 2008 Opt. Precis. Eng. 16 1805 (in Chinese) [姜宝光, 曹召良, 穆全全, 李抄, 夏明亮 2008 光学精密工程 16 1805]
[11] Jorgenson M, Aitken G 1992 Opt. Lett. 17 466
[12] Schwartz C, Baum G, Ribak E N 1994 J. Opt. Soc. Am. A 11 444
[13] Aitken G J, McGaughey D 1995 Proceedings of Topical Meeting on Adaptive Optics 54 89
[14] Paschall R, Anderson D 1993 Appl. Opt. 32
[15] Wild W 1996 Opt. Lett. 21 1433
[16] Dessenne C, Madec P Y, Rousset G 1997 Opt. Lett. 22 1535
[17] Dessenne C, Madec P Y, Rousset G 1998 Appl. Opt. 37 4623
[18] Dessenne C, Madec P Y, Rousset G 1999 Opt. Lett. 24 339
[19] Poyneer L, Véran J 2008 J. Opt. Soc. Am. A 25 1486
[20] Jorgenson M B, Aitken G J M 1992 Proc. SPIE 1706 113
[21] Montera D, Welsh B, Roggemann M, Ruck D 1997 Appl. Opt 36 675
[22] McGuire P, Rhoadarmer T, Coy H, Angel J, Lloyd-Hart M 2000 Proc. SPIE 4007 682
[23] Cheng S Y, Cao Z L, Hu L F, Mu Q Q, Li P F, Xuan L 2010 Opt. Precis. Eng. 18 1060 (in Chinese) [程少园, 曹召良, 胡立发, 穆全全, 李鹏飞, 宣丽 2010 光学精密工程 18 1060]
[24] Li C H, Xian H, Jiang W H, Rao C H 2007 Acta Phys. Sin. 56 4289 (in Chinese) [李超宏, 鲜浩, 姜文汉, 饶长辉 2007 56 4289]
[25] Liu C, Hu L F, Mu Q Q, Cao Z L, Gao F, Wang Y W, Xuan L 2010 Opt. Precis. Eng. 18 2200 (in Chinese) [刘超, 胡立发, 穆全全, 曹召良, 高峰, 王永伟, 宣丽 2010 光学精密工程 18 2200]
[26] Gendron E 1994 Astron. Astrophys. 48 187
[27] Conan J M, Rousset G, Madec P-Y 1995 J. Opt. Soc. Am. A 12 1559
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[1] Love G D 1997 Appl. Opt. 36 1517
[2] Prieto P, Fernandez E, Manzanera S, Artal P 2004 Opt. Express 12 4059
[3] Schmidt J, Goda M, Duncan B 2007 Appl. Opt. 46 2423
[4] Cai D M, Ning N, Jiang W H 2008 Acta Phys. Sin. 57 897 (in Chinese) [蔡冬梅, 凌宁, 姜文汉 2008 57 897]
[5] Li C, Xia M, Mu Q, Jiang B, Xuan L, Cao Z 2009 Opt. Express 17 10774
[6] Liu C, Hu L, Mu Q, Cao Z, Xuan L 2011 Appl. Opt. 50 82
[7] Mu Q, Cao Z, Peng Z, Liu Y, Hu L, Lu X, Xuan L 2010 Opt. Commun. 283 2017
[8] Mu Q, Cao Z, Li D, Hu L, Xuan L 2008 Appl. Opt. 47 4279
[9] Li C, Xia M, Li D, Mu Q, Xuan L 2010 J. Biomed. Opt. 15 046009-1
[10] Jiang B G, Cao Z L, Mu Q Q, Li C, Xia M L 2008 Opt. Precis. Eng. 16 1805 (in Chinese) [姜宝光, 曹召良, 穆全全, 李抄, 夏明亮 2008 光学精密工程 16 1805]
[11] Jorgenson M, Aitken G 1992 Opt. Lett. 17 466
[12] Schwartz C, Baum G, Ribak E N 1994 J. Opt. Soc. Am. A 11 444
[13] Aitken G J, McGaughey D 1995 Proceedings of Topical Meeting on Adaptive Optics 54 89
[14] Paschall R, Anderson D 1993 Appl. Opt. 32
[15] Wild W 1996 Opt. Lett. 21 1433
[16] Dessenne C, Madec P Y, Rousset G 1997 Opt. Lett. 22 1535
[17] Dessenne C, Madec P Y, Rousset G 1998 Appl. Opt. 37 4623
[18] Dessenne C, Madec P Y, Rousset G 1999 Opt. Lett. 24 339
[19] Poyneer L, Véran J 2008 J. Opt. Soc. Am. A 25 1486
[20] Jorgenson M B, Aitken G J M 1992 Proc. SPIE 1706 113
[21] Montera D, Welsh B, Roggemann M, Ruck D 1997 Appl. Opt 36 675
[22] McGuire P, Rhoadarmer T, Coy H, Angel J, Lloyd-Hart M 2000 Proc. SPIE 4007 682
[23] Cheng S Y, Cao Z L, Hu L F, Mu Q Q, Li P F, Xuan L 2010 Opt. Precis. Eng. 18 1060 (in Chinese) [程少园, 曹召良, 胡立发, 穆全全, 李鹏飞, 宣丽 2010 光学精密工程 18 1060]
[24] Li C H, Xian H, Jiang W H, Rao C H 2007 Acta Phys. Sin. 56 4289 (in Chinese) [李超宏, 鲜浩, 姜文汉, 饶长辉 2007 56 4289]
[25] Liu C, Hu L F, Mu Q Q, Cao Z L, Gao F, Wang Y W, Xuan L 2010 Opt. Precis. Eng. 18 2200 (in Chinese) [刘超, 胡立发, 穆全全, 曹召良, 高峰, 王永伟, 宣丽 2010 光学精密工程 18 2200]
[26] Gendron E 1994 Astron. Astrophys. 48 187
[27] Conan J M, Rousset G, Madec P-Y 1995 J. Opt. Soc. Am. A 12 1559
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