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Comparison between iterative wavefront control algorithm and direct gradient wavefront control algorithm for adaptive optics system

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Chinese Physics B 2015年第8期24卷 391-397页

作者：程生毅刘文劲陈善球董理治杨平许冰 laboratory on adaptive optics Institute of Optics and Electronics Chinese Academy of Sciences Key laboratory on adaptive optics Chinese Academy of Sciences University of the Chinese Academy of Sciences

Among all kinds of wavefront control algorithms in adaptive optics systems, the direct gradient wavefront control algorithm is the most widespread and common method. This control algorithm obtains the actuator voltages directly from wavefront slopes through pre-measuring the relational matrix between deformable mirror actuators and Hartmann wavefront sensor with perfect real-time characteristic and stability. However, with increasing the number of sub-apertures in wavefront sensor and deformable mirror actuators of adaptive optics systems, the matrix operation in direct gradient algorithm takes too much time, which becomes a major factor influencing control effect of adaptive optics systems. In this paper we apply an iterative wavefront control algorithm to high-resolution adaptive optics systems, in which the voltages of each actuator are obtained through iteration arithmetic, which gains great advantage in calculation and storage. For AO system with thousands of actuators, the computational complexity estimate is about O(n2) ～ O(n3) in direct gradient wavefront control algorithm, while the computational complexity estimate in iterative wavefront control algorithm is about O(n) ～(O(n)3/2), in which n is the number of actuators of AO system. And the more the numbers of sub-apertures and deformable mirror actuators, the more significant advantage the iterative wavefront control algorithm exhibits.

关键词： adaptive optics iterative wavefront control algorithm direct gradient wavefront control algorithm

A modified phase diversity wavefront sensor with a diffraction grating

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Chinese Physics B 2012年第9期21卷 251-258页

作者：罗群黄林海顾乃庭饶长辉 College of Opto-Electronics Science and Engineering National University of Defense Technology The laboratory on adaptive optics Institute of Optics and ElectronicsChinese Academy of Sciences The Key laboratory on adaptive optics Chinese Academy of Sciences

The phase diversity wavefront sensor is one of the tools used to estimate wavefront aberration, and it is often used as a wavefront sensor in adaptive optics systems. However, the performance of the traditional phase diversity wavefront sensor is limited by the accuracy and dynamic ranges of the intensity distribution at the focus and defocus positions of the CCD camera. In this paper, a modified phase diversity wavefront sensor based on a diffraction grating is proposed to improve the ability to measure the wavefront aberration with larger amplitude and higher spatial frequency. The basic principle and the optics construction of the proposed method are also described in detail. The noise propagation property of the proposed method is also analysed by using the numerical simulation method, and comparison between the diffraction grating phase diversity wavefront sensor and the traditional phase diversity wavefront sensor is also made. The simulation results show that the diffraction grating phase diversity wavefront sensor can obviously improve the ability to measure the wavefront aberration, especially the wavefront aberration with larger amplitude and higher spatial frequency.

关键词： phase diversity wavefront sensor diffraction grating aberration signal-to-noise ratio

First generation solar adaptive optics system for 1-m New Vacuum Solar Telescope at Fuxian Solar Observatory

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Research in Astronomy and Astrophysics 2016年第2期16卷 19-26页

作者： Chang-Hui Rao Lei Zhu Xue-Jun Rao Lan-Qiang Zhang Hua Bao Xue-An Ma Nai-Ting Gu Chun-Lin Guan Dong-Hong Chen Cheng Wang Jun Lin Zen-Yu Jin Zhong Liu Key laboratory on adaptive optics Chinese Academy of Sciences laboratory on adaptive optics Institute of Optics and Electronics Chinese Academy of Sciences Yunnan Astronomical Observatories Chinese Academy of Sciences

The first generation solar adaptive optics （AO） system, which consists of a fine tracking loop with a tip-tilt mirror （TTM） and a correlation tracker, and a high-order correction loop with a 37-element deformable mirror （DM）, a correlating Shack-Hartmann （SH） wavefront sensor （WFS） based on the ab- solute difference algorithm and a real time controller （RTC）, has been developed and installed at the 1-m New Vacuum Solar Telescope （NVST） that is part of Fuxian Solar Observatory （FSO）. Compared with the 37-element solar AO system developed for the 26-cm Solar Fine Structure Telescope, administered by Yunnan Astronomical Observatories, this AO system has two updates： one is the subaperture arrangement of the WFS changed from square to hexagon; the other is the high speed camera of the WFS and the corre- sponding real time controller. The WFS can be operated at a frame rate of 2100 Hz and the error correction bandwidth can exceed 100 Hz. After AO correction, the averaged residual image motion and the averaged RMS wavefront error are reduced to 0.06＂ and 45 nm, respectively. The results of on-sky testing obser- vations demonstrate better contrast and finer structures of the images taken with AO than those without AO.

关键词： adaptive optics -- high angular resolution -- sunspots -- granulation

37-element solar adaptive optics for 26-cm solar fine structure telescope at Yunnan Astronomical Observatory

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Chinese optics Letters 2010年第10期8卷 966-968页

作者：饶长辉朱磊饶学军官春林陈东红林隽刘子忠 Key laboratory on adaptive optics Chinese Academy of Sciences laboratory on adaptive optics Institute of Optics and Electronics Chinese Academy of Sciences Yunnan Astronomical Observatory National Astronomical Observatories Chinese Academy of Sciences

A 37-element solar adaptive optics （AO） system was built and installed at the 26-cm solar fine structure telescope of Yunnan Astronomical Observatory. The AO system is composed of a fine tracking loop with a tip/tilt mirror and a correlation tracker, a high-order correction loop with a 37-element deformable mirror, a correlating Shack-Hartmann wavefront sensor based on the absolute difference algorithm, and a real time controller. The system was completed on Sep. 28, 2009 and was used to obtain AO-corrected high-resolution solar images. The contrast and resolution of the images are clearly improved after wavefront correction by AO. To the best of out knowledge, this system is the first solar AO system in China.

关键词： adaptive optics Buildings Mirrors Optical telescopes Wavefronts

Data point selection for weighted least square fitting of cavity decay time constant

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Chinese Physics B 2016年第1期25卷 640-646页

作者：何星晏虎董理治杨平许冰 laboratory on adaptive optics Institute of Optics and ElectronicsChinese Academy of SciencesChengdu 610209China Key laboratory on adaptive optics Chinese Academy of SciencesChengdu 610209China University of the Chinese Academy of Sciences Beijing 100039China

For the accurate extraction of cavity decay time, a selection of data points is supplemented to the weighted least square method. We derive the expected precision, accuracy and computation cost of this improved method, and examine these performances by simulation. By comparing this method with the nonlinear least square fitting （NLSF） method and the linear regression of the sum （LRS） method in derivations and simulations, we find that this method can achieve the same or even better precision, comparable accuracy, and lower computation cost. We test this method by experimental decay signals. The results are in agreement with the ones obtained from the nonlinear least square fitting method.

关键词： cavity ring-down decay time extraction weighted least square method data point selection

Error analysis of the piston estimation method in dispersed fringe sensor

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Chinese Physics B 2017年第3期26卷 620-626页

作者：李杨王胜千饶长辉 laboratory on adaptive optics Institute of Optics and Electronics Chinese Academy of Sciences Chengdu 610209 China Key laboratory on adaptive optics Chinese Academy of Sciences Chengdu 610209 China University of Chinese Academy of Sciences Beijing 100049 China

Dispersed fringe sensor （DFS） is an important phasing sensor of next-generation optical astronomical telescopes. The measurement errors induced by the measurement noise of three piston estimation methods for the DFS including leastsquared fitting （LSF） method, frequency peak location （FPL） method and main peak position （MPP） method, are analyzed theoretically and validated experimentally in this paper. The experimental results coincide well with the theoretical analyses. The MPP, FPL, LSF are used respectively when the DFS operates with broadband light （central wavelength： 706 nm, bandwidth： 23 nm）. The corresponding root mean square （RMS） value of estimated piston error can be achieved to be 1 nm, 3 nm, 26 nm, respectively. Additionally, the range of DFS with the FPL can be more than 100 μm at the same time. The FPL method can work well both in coarse and fine phasing stages with acceptable accuracy, compared with LSF method and MPP method.

关键词： adaptive and segmented optics telescopes interferometer phase measurement

adaptive optics optical coherence tomography for retina imaging

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Chinese optics Letters 2008年第6期6卷 424-425页

作者：史国华戴云王玲丁志华饶学军张雨东 The laboratory on adaptive optics Institute of Optics and ElectronicsChinese Academy of Sciences State Key laboratory of Modern Optical Instrumentation Zhejiang University

When optical coherence tomography （OCT） is used for human retina imaging, its transverse resolution is limited by the aberrations of human eyes. To overcome this disadvantage, a high resolution imaging system for living human retina, which consists of a time domain OCT system and a 37-elements adaptive optics （AO） system, has been developed. The AO closed loop rate is 20 flames per second, and the OCT has a 6.7-μm axial resolution. In this paper, this system is introduced and the high resolution imaging results for retina are presented.

关键词： Arctic engineering Computer networks Diagnostic radiography Medical imaging Optical tomography Optoelectronic devices Tomography

An adaptive laser beam shaping technique based on a genetic algorithm

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Chinese optics Letters 2007年第9期5卷 497-500页

作者：杨平刘渊杨伟敖明武胡诗杰许冰姜文汉 laboratory on adaptive optics Institute of Optics and ElectronicsChinese Academy of Sciences

A new adaptive beam intensity shaping technique based on the combination of a 19-element piezo-electricity deformable mirror （DM） and a global genetic algorithm is presented. This technique can adaptively adjust the voltages of the 19 actuators on the DM to reduce the difference between the target beam shape and the actual beam shape. Numerical simulations and experimental results show that within the stroke range of the DM, this technique can be well used to create the given beam intensity profiles on the focal plane.

关键词： GA An adaptive laser beam shaping technique based on a genetic algorithm Figure FDM

Ground-layer adaptive optics for the New Vacuum Solar Telescope:Instrument description and first results

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Science China(Physics,Mechanics & Astronomy) 2023年第6期66卷 200-210页

作者： Lanqiang Zhang Hua Bao Xuejun Rao Youming Guo Libo Zhong Xian Ran Nanfei Yan Jinsheng Yang Cheng Wang Jiahui Zhou Ying Yang Yunyao Long Xinlong Fan Zhongyi Feng Donghong Chen Changhui Rao The Key laboratory on adaptive optics Chinese Academy of SciencesChengdu 610209China The Laboratryon adaptive optics Institute of Optics and ElectronicsChinese Academyof SciencesChengdu 629China University of Chinese Academy of Sciences Beijing 100049China

Ground-layer adaptive optics(GLAO)has shown its potential for use in solar observation owing to its wide field-of-view(FOV)correction.A high-order GLAO system that consists of a multiple direction Shack-Hartmann wavefront sensor(WFS),a realtime controller with a multi-CPU processor,and a 151-element deformable mirror was developed for the 1-m New Vacuum Solar Telescope at Yunnan Observatories,Chinese Academy of Sciences.A hexagonal microlens with 9×8 subapertures is employed in the *** detection FOV is 42′′×37′′,in which 9(3×3)guide regions are extracted for multiple direction wavefront sensing with a frame rate of up to 2200 *** our knowledge,this is the first professional solar GLAO system used as a regularly operating instrument for scientific *** installation and adjustment were performed in the summer of *** this article,a detailed account of the GLAO system and its first light results and a comprehensive analysis of the performance of the GLAO system are *** results show that this system can effectively improve the imaging quality after compensating for the wavefront aberration due to ground-layer turbulence.

关键词： adaptive and segmented optics solar instruments astronomical observations