10m大口径薄膜衍射主镜的色差校正技术研究

分析了薄膜衍射主镜的成像性能及色散特性,利用含有衍射面的反射式消色差光路校正了衍射主镜的强色散,使成像系统的工作波段达到40nm、视场达到0.02°,设计了10m口径、115.73m总长的短结构合成孔径薄膜衍射成像系统.结果表明,消色差光路将两边缘波长0.58μm与0.62μm之间的焦距差由5.34m减小到17.27μm.该研究提供了一种薄膜衍射主镜成像系统的设计方案,可为超大口径薄膜衍射成像系统的工程化研究提供参考.     

高衍射效率衍射望远镜系统的设计/加工及成像性能测试

为提高衍射效率,设计并制作了口径为300mm的衍射成像系统.该系统的物镜是由一块四台阶位相型菲涅尔波带片通过激光直写套刻和Ar离子束物理刻蚀技术在石英玻璃基板上加工而成.测试了衍射物镜的衍射效率,实验结果表明:衍射物镜在波长632.8nm处的衍射效率为66.4%,达到理论值的82%.搭建了衍射成像系统光路,分别采用10μm星点孔与分辨率板,测试了系统的成像性能.实验测得星点像直径为44μm,分辨率板的极限分辨率达到84lp/mm,接近该系统的理论计算值,表明该衍射成像系统具有较好的成像性能.     

光子集成干涉成像系统微透镜排布设计与图像复原

光子集成干涉成像系统体积小、重量轻、功耗小,且系统分辨率不受单个透镜口径尺寸的限制,是一种新兴的成像技术.针对光子集成干涉成像系统图像复原问题,开展了图像复原技术和微透镜阵列最优排布研究,提出了基于压缩感知的光子集成干涉成像图像恢复技术,以及基于图像残差的最优微透镜阵列排布设计评估方法;通过计算仿真,可实现在有限空间体...     

超分辨率复原方法相关原理研究

介绍了超分辨率复原方法的概念和理论基础;重点总结了常用的超分辨率复原方法,并对相关的理论依据、优缺点和适用范围进行了详尽分析;对超分辨率复原方法的未来发展进行了展望.超分辨率复原方法分为频域法和空域法.频域复原法原理简单清楚,计算方便,但是所建立的运动模型都是平移模型,不具有一般性,同时难以利用正则化约束,因而导致难以使用图像的先验信息进行超分辨率复原.空域复原法可以很方便地建立复杂的运动模型,同时考虑了几乎所有的图像降质因素,例如噪声、降采样、由非零孔径时间造成的模糊、光学系统降质和运动模糊等,还可以加入更完善的先验知识,相比于频域复原法,空域超分辨率复原模型更符合实际的图像退化过程,是目前应用最广泛的一类超分辨率复原方法.     

基于小波阈值法和维纳滤波的稀疏孔径光学系统成像的恢复

在研究稀疏孔径理想衍射成像光学系统的基础上，提出基于改进小波阈值法和维纳滤波的稀疏孔径光学系统成像恢复算法。针对存在噪声干扰的稀疏孔径光学成像系统，设计并利用改进的小波阈值去噪算法，较好地去除了成像噪声，最大程度地得到较为理想的成像结果，然后利用维纳滤波方法实现成像恢复。在实验中，利用光学设计软件ZEMAX设计了不同填充因子的稀疏孔径光学系统，并用本算法进行了成像恢复。实验结果表明，该算法的结果优于单独使用维纳滤波方法所获得的结果。     

Large aperture phase-coded diffractive lens for achromatic and 16° field-of-view imaging with high efficiency

Diffractive lenses (DLs) can realize high-resolution imaging with light weight and compact size. Conventional DLs suffer large chromatic and off-axis aberrations, which significantly limits their practical applications. Although many achromatic methods have been proposed, most of them are used for designing small aperture DLs, which have low diffraction efficiencies. In the designing of diffractive achromatic lenses, increasing the aperture and improving the diffraction efficiency have become two of the most important design issues. Here, a novel phase-coded diffractive lens (PCDL) for achromatic imaging with a large aperture and high efficiency is proposed and demonstrated experimentally, and it also possesses wide field-of-view (FOV) imaging at the same time. The phase distribution of the conventional phase-type diffractive lens (DL) is coded with a cubic function to expand both the working bandwidth and the FOV of conventional DL. The proposed phase-type DL is fabricated by using the laser direct writing of grey-scale patterns for a PCDL of a diameter of 10 mm, a focal length of 100 mm, and a cubic phase coding parameter of 30π. Experimental results show that the working bandwidth and the FOV of the PCDL respectively reach 50 nm and 16° with over 8% focusing efficiency, which are in significant contrast to the counterparts of conventional DL and in good agreement with the theoretical predictions. This work provides a novel way for implementing the achromatic, wide FOV, and high-efficiency imaging with large aperture DL.     

大口径折反式中波红外衍射望远镜系统设计

为实现空间红外望远镜的高分辨率探测,基于Schupmann消色差理论,开展了大口径折反式中波红外衍射望远镜系统的设计及消热差模型研究。设计了口径1 m、F数为2、全视场0.12°、波段3.8 μm～4.2 μm的折反式中波红外衍射望远镜系统,其主镜及校正镜均为平面衍射透镜,中继系统采用卡塞格林折反式结构,再聚焦及三次成像系统均为折射式结构,对系统进行了公差、鬼像及冷反射分析。设计结果表明:在?20 ℃～60 ℃温度下,系统的MTF在16.7 lp/mm范围内均大于0.7,接近衍射极限,且具有100%冷屏效率,公差满足现有加工装配水平;鬼像能量为0.1%,对目标信号的影响较小;冷反射等效温差（NITD）随温度的变化量小于探测器噪声等效温差（NETD）。该系统可为更大口径红外衍射望远镜系统的设计提供参考。     

去散焦模糊的折反射全向成像系统设计

随着高分辨率传感器和大光圈的采用,光圈和反射面曲率造成的折反射全向成像散焦模糊问题越发突出。提出了一种有效去除散焦模糊的折反射全向成像系统设计。理论分析折反射成像散焦模糊的原因,建立全向图点扩展函数与实景空间物点及成像系统虚像位置的关系;在一次曝光成像时间内匀速旋转镜头对焦环,通过累积曝光使全向图散焦模糊核具有期望的空间不变性;利用反卷积算法对散焦模糊全向图进行复原,得到全局清晰的全向图像。该方法较好地解决了折反射全向成像散焦模糊问题,对提高折反射全向成像质量,促进其在相关领域的广泛应用具有重要意义。     

基于非球面基底的红外谐衍射元件设计

根据谐衍射透镜的特点以及非球面校正像差的独特性能,将谐衍射面制作在非球面基底上制成单透镜,该单透镜应用于红外系统中,能够在两个波段1．8～2．4μm和3．4～4．8μm内同时较好地校正系统的色差,有效地校正此单片镜系统的像差,在设计波段内大幅度提高了衍射效率,成像质量接近衍射极限。     

X射线编码孔径成像中的一种高精度图像重构方法

在惯性约束聚变实验的过程诊断研究中,采用环形编码孔径成像技术可以同时获得高的空间分辨力和时间分辨力。获得高的空间分辨力的关键之一是如何准确地获得目标的点扩展函数。通常采用直接投影法。但这种方法忽略了X射线的衍射效应,因此限制了分辨力的提高。依据光的标量衍射理论,考虑X射线的衍射效应,导出了环形编码孔径的点扩展函数。并在此基础上制作了维纳滤波器。在激光等离子体重点实验室,用内直径为250μm,外直径为260μm的环形孔径板,对惯性约束聚变（ICF）的过程进行成像实验,得到了靶标的编码图像。采用以衍射为基础的维钠滤波器进行重构,获得的重构图像明显的优于用直接投影法得到的结果。     

大口径红外离轴三反光学系统设计及公差分析

在空间光学领域中,光学系统的发展趋势为长焦距、大视场、轻量化、大相对孔径、高成像质量等。为适应该发展趋势,对大口径反射式光学系统进行研究,在共轴三反系统的成像理论基础上,为避免中心遮拦,提高成像质量,采用视场离轴方式,设计了一款大口径离轴三反式光学系统。该光学系统在奈奎斯特空间频率17 lp/mm处,光学传递函数MTF大于0.75,成像质量接近衍射极限。此外,光学系统公差的合理分配是影响相机总体性能的主要因素,运用公差灵敏度分析和反转灵敏度分析,计算各公差对光学系统成像质量的影响,给出了合适的公差分配,经过模拟分析,按照给定的公差加工装调,系统光学传递函数大于0.55。     

Compound diffractive telescope system: design, straylight analysis, and optical test

The compound diffractive telescope is a novel space optical system which combines the structure of compound eyes with diffractive optics and so it has a lighter weight, a wider field of view (FOV), a lower cost as well as looser fabrication tolerance. In this paper, the design of a compound diffractive telescope composed of one primary lens and twenty-one eyepieces is introduced. Then the influence of diffraction orders on the performance of the system is analysed. A modified phase function model of diffractive optics is proposed to analyse the modulation transfer function (MTF) curves for 0℃ FOV, which provides a more accurate prediction of the performance of the system. In addition, an optimized mechanism is also proposed to suppress stray light. The star image and resolution tests show that the system can achieve diffraction limit imaging within ± 2℃ of FOV and ±4~mm of eccentricity. Finally, a series of pictures of an object are taken from different channels, and the splicing of pictures from adjacent FOVs is demonstrated. In summary, the designed system has been proved to have great potential applications.     

基于固定校正镜的折衍共形光学系统设计

设计了一个大扫描视场的折衍混合红外共形光学系统,共形成像系统工作波段为3.7～4.8 m,相对孔径为1/2,焦距为120 mm,扫描视场为40。由于共形光学系统具有大偏心、大倾斜光学特性,像差校正难度较大,设计中采用固定校正镜和折衍混合混合结构校正了共形光学元件的像差,引入了非球面和衍射面有效消除了各个扫描视场的像差。设计结果表明:光学系统光阑与探测器冷光阑重合,满足100%冷光阑效率。在40扫描视场范围内,共形光学系统的光学传递函数曲线接近衍射极限,成像良好。     

Effects of fabrication errors on diffraction efficiency for a diffractive membrane

The demand for space-borne telescopes with an aperture of 20 m is forcing the development of large diameter diffractive Fresnel zone lenses(FZLs) on membranes. However, due to the fabrication errors of multi-level microstructures, the real diffraction efficiency is always significantly smaller than the theoretical value. In this Letter,the effects of a set of fabrication errors on the diffraction efficiency for a diffractive membrane are studied. In order to verify the proposed models, a 4-level membrane FZL with a diameter of 320 mm is fabricated. The fabrication errors of the membrane FZL are measured, and its diffraction efficiency in the +1 order is also tested.The results show that the tested diffraction efficiency is very close to the calculated value based on the proposed models. It is expected that the present work could play a theoretical guiding role in the future development of space-borne diffractive telescopes.     

基于改进维纳逆滤波的衍射成像光谱仪数据误差分析与重构

衍射成像光谱仪探测到的高光谱数据需要进行计算与反演才可以得到成像光谱数据,本文对衍射成像光谱仪的成像过程及数据误差产生的原理从空间维和光谱维两方面进行了分析,并针对其光谱重构过程中系统点扩散函数标准差较大时重构结果清晰度较低、存在振铃等问题,提出了基于改进维纳逆滤波的光谱数据重构算法,该方法在分析衍射成像光谱仪数据特点与误差的基础上,将每一次维纳逆滤波的重构结果视为新的模糊图像,利用成像过程及维纳逆滤波的基本原理确定新的模糊图像对应的点扩散函数,反复进行维纳逆滤波达到提高图像清晰度的效果,再根据图像自身的空间和光谱特征分布,进行自适应性的噪声去除.利用模拟的衍射成像光谱数据进行验证,在系统点扩散函数的标准差为2.5的情况下,能得到无振铃的重构结果,且与传统维纳逆滤波法的重构结果进行比较,清晰度、细节能力等指标均有所提高,满足了衍射成像光谱数据应用需求.     

RGB三通道衍射望远镜光学成像系统设计

基于目前研究较热的大口径衍射望远镜技术，提出一种在可见光范围内进行成像的衍射望远镜光学系统方案。该方案解决了目前衍射望远镜存在的成像频谱范围较窄的问题，可以在可见光范围内获取彩色图像，设计方法是将衍射元件沿径向分为3个通道，分别对R、G、B三个颜色通道进行成像，每个通道的成像带宽为40 nm，通过控制系统参数使3个通道的像在像面处重合，获取彩色图像。设计了基于25 m口径衍射主镜的三通道望远镜光学系统，并对该系统进行建模仿真，仿真结果与设计理论相符。该方案可以增加成像的频谱范围，其像面光斑具有与单通道系统像面光斑近乎相同的主瓣宽度。     

Design and energy analysis of interference imaging system with annular-aperture

An interference imaging system with annular aperture is presented having focal length of 6000 mm, aperture of 1000 mm, and ring width/semi-diameter of 0.2. The energy analyze is carried out to evaluate the optical performance of this system, and imaging restoration processing is also performed by the blind deconvolution algorithm with iteration number of 25. Results show that the quality is close to the diffraction limit and the weight has greatly reduced to 36% of the full-aperture system, which verifies the annular aperture system is a better choice for the space telescope with large-caliber and long focal length.     

离轴三反红外双波段景象模拟器光学系统设计

 针对红外双波段成像系统性能测试与评估的应用需求,设计了3 μm～5 μm和8 μm～12 μm红外双波段视景仿真用离轴三反光学系统。在共轴三反光学系统成像理论基础上,分析了孔径光栏远离主镜的离轴三反系统像差特性,研究了大出瞳距、大相对孔径条件下离轴三反光学系统的结构设计和像差平衡方法。系统焦距为330 mm,F#为3,视场为6°×4.5°,出瞳距为750 mm,在空间频率10 lp/mm 处,中波红外MTF>0.65,长波红外MTF>0.4,接近衍射极限。具有大视场、大出瞳距、高分辨率、结构紧凑等特点。     

Hybrid division of aperture/division of a focal-plane polarimeter for real-time polarization imagery without an instantaneous field-of-view error

The direct, instantaneous measurement of the Stokes parameters of optical radiation is not possible using only a single detector. To infer the Stokes parameters in an image, the optical intensity must be modulated in time, space, or spectral characteristics and multiple measurements must be made on a pixel-by-pixel basis across the scene. Most existing imaging polarimetry strategies generally suffer from either spatial or temporal misregistration. Those strategies that do not suffer from misregistration have severe restrictions placed on the spectral properties of the illumination and/or optical system. A hybrid polarimeter is proposed that can be used for broadband imaging applications that, in principle, can be made without any temporal or spatial misalignment and that does not require detailed knowledge of the spectral properties of the radiation. The strategy uses arrays of microlenses and micropolarizers to create a high-resolution spatial array of nonimaging division of aperture polarimeters.     

PSF-based restoration with edge adaptive regularization for structured light measurement

Edge information is important for measurement based on structured light. The presented effort puts forward an image restoration method with edge regularization for structured light measurement, which detects the edge of image, then updates the parameters of image degradation model and restores results in iteration. The diffraction limit of optics and nonlinear distortion of sensors are calculated as prior knowledge for semi-blind deconvolution. Blur metric is introduced for constraints of deconvolution iterations. Images before and after restoration are sent to shape recognition and automatic calibration modules for comparison. From experimental results we can conclude that the proposed approach can effectively enhance image quality and edge details, so that greater precision can be achieved.