应用闭环残余倾斜数据分析自适应光学系统精跟踪回路性能

在自适应光学系统中,目标跟踪误差主要由未完全补偿的大气湍流扰动和望远镜抖动引起的跟踪误差以及系统的倾斜噪声误差两部分组成。提出一种用闭环残余倾斜数据计算倾斜噪声误差、大气湍流扰动和望远镜抖动引起的跟踪误差以及系统跟踪残余误差的新方法,并用此方法分析61单元自适应光学系统中精跟踪回路的性能。     

测量噪声对波前重构精度的影响

 Hartmann-Shack波前传感器斜率测量误差是自适应光学系统中影响波前重构精度的一个主要误差来源。针对模式法波前重构算法,推导出了普遍适用的模式法波前重构误差传递系数计算公式;利用61单元自适应光学系统中的Hartmann-Shack波前传感器测量的斜率数据,验证了模式法波前重构误差传递系数计算公式的正确性。     

Combinational-deformable-mirror adaptive optics system for compensation of high-order modes of wavefront

A new kind of adaptive optics (AO) system, in which several low spatial frequency deformable mirrors(DMs) with optical conjugation relationship are combined to correct high-order aberrations, is proposed.The phase compensation principle and the control method of the combinational AO system are introduced.The numerical simulations for the AO system with two 60-element DMs are presented. The results indicate that the combinational DM in the AO system can correct different aberrations effectively as one single DM with more actuators, and there is no change of control method. This technique can be applied to a large telescope AO system to improve the spatial compensation capability for wavefront by using current DM.     

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

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.     

Progress in Space Solar Telescope

In this paper we will summarize the progress in the development of the Chinese Space Solar Telescope (SST) during the past few years. The main scientific objective of SST is to observe the fundamental structure of solar magnetic field with its 1-m optical telescope. The success of 1-m Swedish Solar Telescope and Hinode underscores the importance of this 1-m space telescope. In addition, some key technical problems have been solved.     

A wavefront sensor-less adaptive optical system for a solid-state laser

A wavefront sensor-less adaptive optical system has been set up. It consists of a deformable mirror, a high-voltage amplifier, a set of solid-state laser system, a CCD camera, control software and a genetic algorithm. This adaptive optical system does not employ a wavefront sensor to detect the wavefront information, but optimizes the light intensity within a fixed aperture in the focal plane by a 19-element piezoelectricity deformable mirror. A genetic algorithm is introduced to search the optimum surface profile of the deformable mirror for correcting the phase aberrations in a solid-state laser system. The far-field light intensity signal, which is measured by a CCD, is taken as the fitness function of the genetic algorithm. In this paper, the performance and the efficiency of this wavefront sensor-less adaptive optical system are presented. Both simulative results and experimental results are given and discussed.     

Sky implementation of modal predictive control in adaptive optics

We present what we believe are the first experimental results obtained with modal linear predictive control of an adaptive optics system operating on sky at a visible wavelength on a 1.52-m telescope (Observatoire de Haute-Provence, France). This system yields substantially better results than optimized integral control: a 30% relative gain in Strehl ratio is measured, even in conditions of low wind speed.     

600mm望远镜液晶自适应系统成像光路设计

为了与600 mm望远镜匹配以验证液晶自适应光学的有效性,利用Zemax光学设计软件进行了液晶自适应光学系统的设计和优化.根据望远镜的参量、大气湍流的特性和液晶的特点提出设计要求,然后进行光学系统设计和Zemax软件模拟优化,设计出了满足要求的系统.对该光学系统进行性能评价.设计出的系统与望远镜的组合焦距为35 m, F数为58.求得光学系统在像面处的极限线分辨力为44.8 μm,成像CCD的像元尺寸为16 μm,满足采样定理.液晶自适应光学系统的调制传递函数与衍射极限传递函数非常接近,而且系统的光程差像差在0.1λ左右,说明系统具备优良的光学性能.     

一种结合图像复原技术的自适应光学系统控制方法

在天文高分辨成像领域,自适应光学校正和事后图像复原都必不可少,但传统的自适应光学系统控制方法以提升光学成像质量为目的,并未考虑图像复原环节,因此,研究一种结合两者以获得高质量复原图像为目标的控制方法具有重要意义.本文对传统自适应光学技术结合事后图像解卷积的方法进行了分析,阐述了其存在的缺陷.首次提出了将自适应光学技术和图像复原技术相结合进行系统分析的思想,并提出了变形镜校正度(变形镜控制电压相对于传统方法控制电压的缩放比例)的概念,通过改变校正度可实现变形镜校正残差和波前传感器探测误差的调整,同时证明了复原图像质量在校正度下降的方向存在一个最优值,用最优校正度来修正变形镜控制电压,就得到了一种新的控制方法.针对点源目标成像,仿真表明该方法相比于传统方法,能够得到质量更好的复原图像.     

Adaptive phase-distortion correction based on parallel gradient-descent optimization

We describe an adaptive wave-front control technique based on a parallel stochastic perturbation method that can be applied to a general class of adaptive-optical system. The efficiency of this approach is analyzed numerically and experimentally by use of a white-light adaptive-imaging system with an extended source. To create and compensate for static phase distortions, we use 127-element liquid-crystal phase modulators. Results demonstrate that adaptive wave-front correction by a parallel-perturbation technique can significantly improve image quality.     

A helium-3 cooled bolometer system for one millimeter continuum observations

A new, 1-mm-continuum, bolometer detector system has been constructed employing internal adsorption pumping of He-3 to reach an operating temperature close to 0.4 K. The system spectral bandwidth is 800 to 1200 m. Although the system was originally designed to be used on the 5-m Hale telescope, it has also been successfully used on the 4-m Anglo-Australian telescope and on the 10-m dish at Owens Valley, California. At the 5-m Hale telescope, the system has a full width-half maximum (FWHM) beam size of 55t" and an instantaneous noise-equivalent flux density of 6 in good weather.     

红外自适应系统中双波段望远镜与红外物镜设计

大孔径红外光学系统往往易受自重和环境温度影响造成像质恶化,引入自适应光学技术的红外自适应系统能够很好地解决该问题,为此设计了一个用于Hartmann-Shack波前检测的红外自适应光学系统。重点设计了10×可见光与中波红外双波段望远镜,物镜为卡赛格林反射物镜组,无需消色差,在可见光与中波红外2个波段实现了消色差目镜设计;还设计了红外成像中继光学系统,可实现100%冷光阑效率,并补偿望远镜在中波红外波段的残余像差,使最终设计的光学系统MTF接近衍射极限,达到了0.5以上,满足设计指标要求。     

自适应光学系统校正后实际分辨率评价指标

为了评价地基大口径望远镜对空间目标自适应光学系统校正后的实际分辨率,提出了可分辨单元数比指标。结合1.23 m自适应光学望远镜的观测数据,对可分辨单元数比的物理意义、适用范围、误差影响因素以及大气弥散的影响进行了分析。结果表明：可分辨单元数比能全面反映望远镜系统对空间目标自适应校正后的实际分辨率,且物理意义更直观;适用于所有可获取波前特征的望远镜自适应校正后实际分辨率的评估;其误差主要依赖于波前探测器的测量误差;大气弥散对其影响可忽略。     

用于活体人眼视网膜观察的自适应光学成像系统

利用自适应光学技术,研制了两套活体人眼视网膜高分辨力成像系统,在实时校正人眼波前误差的基础上,实现活体人眼视网膜细胞尺度的高分辨力成像。这两套系统分别采用19和37单元小型压电变形反射镜作为波前校正元件,哈特曼-夏克(Hartmann-Shack)波前传感器测量波前误差,用眼底反射的半导体激光作为波前探测的信标。在用计算机控制自适应光学系统实现人眼波前误差校正后,触发闪光灯照明视网膜,用CCD相机记录视网膜的高分辨力图像。校正后的残余波前误差的均方根值已分别小于1／6和1／10波长,相当于视网膜上成像分辨力分别为3．4μm和2．6μm,接近衍射极限。试验表明37单元系统的成像质量更好。     

3.5 m口径空间望远镜单块式主镜技术展望

主反射镜的口径大小与结构形式在极大程度上决定了空间望远镜的技术难度与经济成本。为了实现更高的空间分辨率与更强的信息收集能力,各国研制的空间望远镜主反射镜的口径朝着越来越大的趋势发展,从“哈勃空间望远镜”（HST）的2.4 m,到“新世界观测者空间望远镜”（NWO）的4 m,甚至到“先进技术大口径空间望远镜”（ATLAST）的8 m,无不体现了对超大口径空间观测能力的追求。而单块式主镜凭借其支撑技术的可靠性与经济性,正成为超大口径空间望远镜的首选。通过对国外研制的超大口径空间望远镜的论述与分析,探讨了目前空间望远镜中超大口径主反射镜的关键技术与发展方向。针对目前国内运载能力与光学制造加工能力的极限,提出了建造基于3.5 m口径主镜的空间望远镜设想。     

偏振滤波白天抑制天光背景作用分析

由于天文观测领域大部分自适应光学系统只能在夜晚工作,提出了采用偏振滤波技术抑制天光背景的办法以达到白天探测微弱星体目标的目的。介绍了偏振滤波的原理并估算了抑制天光背景的效果,通过观测角度关系得到了偏振方位角的计算公式,并在丽江观测站1.8m望远镜自适应光学系统平台上进行实验,给出了消像旋模型。实验结果表明,偏振滤波技术能有效抑制天光背景,提高星体目标探测能力,一定程度上提高了自适应光学系统在白天探测弱小星体目标的可能性。     

600mm自适应望远镜最佳子孔径数仿真研究

基于自适应光学望远镜的成像特性,分析像斑中心亮度最大以及剩余波前误差最小两种情况下望远镜变形镜的最佳子孔径数范围,利用ZEMAX软件对驱动单元正三角形和矩形布局的变形镜波前校正进行仿真模拟,通过对含高速倾斜镜和不含高速倾斜镜两种情况下望远镜的分析,得到600mm自适应望远镜的最佳子孔径数。     

Laser reference stars for ground-based astronomic telescopes

Problems of construction of an up-to-date ground-based adaptive telescope equipped with an additional optical system for the formation of a laser reference star are studied. The systems proposed for laser reference star formation allow information on the wavefront tilt to be obtained.     

Wind measurements with 355-nm molecular Doppler lidar

A Doppler lidar system based on the molecular double-edge technique is described. The system is mounted in a modified van to permit deployment in field operations. The lidar operates with a tripled Nd:YAG laser at 355 nm, a 45-cm-aperture telescope, and a matching azimuth-over-elevation scanner to permit full sky access. Validated atmospheric wind profiles were measured from 1.8 to 35 km with a 178-m vertical resolution. The range-dependent rms deviation of the horizontal wind speed is 0.4-6 m/s. The measured wind speed and direction are in good agreement with the rawinsonde wind measurements made simultaneously from the same location.     

Concept for testing two-mirror optical telescopes

A concept for testing a two-mirror telescope optical system and its optical components is proposed. The example of the space ultraviolet Ritchey-Chretien telescope, with a primary mirror of 170 cm diameter, is considered. The principal propositions of the concept, and the optical schematic diagrams of the independent and mutual testing of the primary and secondary telescope mirrors, are discussed. Constructional data are presented of optical testing systems, with a minimum number of auxiliary optical elements of simple configuration. When designing the optical testing system, the principle of the null test method has been used. According to this principle the object to be tested and the auxiliary optical elements form a system that is free of aberration for a given kind of ray path. This makes it possible to use various methods and instruments intended for testing aberration free optical systems, for example, Twyman-Green and Fizeau interferometers, Foucault or knife edge test, and star tests^1–4.