Temporal ghost imaging of a time object,dispersion cancelation,and nonlocal time lens with bi-photon state

We present a theory of temporal diffraction, temporal imaging of a bi-photon state, and temporal ghost imaging of a time object. By applying factional Fourier transform to the bi-photon wave packet propagating in space, we could obtain a theory that shows the physical origin of dispersion cancelation, temporal imaging, nonlocal effects of time lenses, and temporal ghost imaging. We introduce the temporal diffraction distance for bi-photon wave packet and show that the bi-photon wave packet behaves like a single wave packet whose temporal diffraction distance is determined by the coherent sum of the temporal diffraction distances for the signal and the idler beams. This property yields the well known dispersion cancelation, the recovery of original bi-photon wave packet in temporal imaging, and the nonlocal combination of two time lenses placed in different arms. We also propose a method for ghost imaging of an arbitrary time object.     

强度关联三维衍射层析的实验研究

提出了一种基于强度关联成像的新型三维衍射层析技术.利用强度关联成像技术(鬼成像)可实现无透镜傅里叶变换的特点,并结合衍射层析技术和二步相位恢复算法,使用波长为650 nm的赝热光实现了强度关联三维衍射层析.详细描述了强度关联三维衍射层析的基本原理以及具体实验结果,为在第三代同步辐射光源实现非相干X光衍射成像积累了经验.     

X光能点、放大倍率及针孔尺寸对空间分辨的影响

X光针孔成像是惯性约束聚变(ICF)研究中重要的诊断方法,对其点扩散函数的计算可用于图像重建和系统空间分辨的判断。对菲涅耳衍射公式进行了化简,分析了X光能点、针孔尺寸及放大倍率对针孔点扩散函数的影响。实验在保证成像能获得足够高信噪比的条件下,通过模拟获得在最佳空间分辨时所要的针孔大小、放大倍率和X光能点等参数。在流体力学不稳定性的静态样品定标实验中,通过模拟获得了针孔的调制传递函数(MTF),结合实验测量的结果反推获得分幅相机本身的MTF值。同时采用测刀边函数的方法获得了分幅相机本身的刀边函数,进而得到相机在各空间频率下的MTF值。两种方法得到的分幅相机MTF值一致,验证了通过菲涅耳衍射模拟X光针孔成像的可行性。     

利用波矢滤波超表面实现超衍射成像

超衍射成像是当前光学领域的研究热点.本文利用一种不对称分裂环超表面结构来实现超衍射成像,该结构由上下两个不对称的金属环组成,通过集体陷模共振可实现对入射光的波矢选择性透过.当物体发出或反射的光照射到超表面上时,入射角大于某一角度的入射光会被共振电场耦合吸收或反射,只有低空间频率的光波可以通过,从而减小衍射的影响,实现超衍射成像.数值模拟结果表明了这一方法的可行性.     

成像型声光可调谐滤光器关键性能指标测试方法研究

成像型声光可调谐滤光器(acousto-optic tunable filter, AOTF)是近年来发展起来的一种十分重要的新型光谱成像仪器滤光器件。文章分析了成像型AOTF的基本工作原理,并研究了一套AOTF关键性能如衍射效率、波长温漂、空间衍射效率均匀性、图像漂移等指标的测试方法。     

用菲涅耳衍射理论分析双光栅成像效应

从理论上对双光栅成像效应现象进行研究,分别从菲涅耳衍射理论和平面透射光栅的菲涅耳衍射公式出发,分析了物光波经过两个平行放置的平面透射光栅组成的系统衍射后的复振幅分布。分析结果表明,在理想状态下,当两个光栅的放置位置满足一定条件时,在第二个光栅后面可以观察到一个清晰的原物体图像。理论分析解释了两个光栅在双光栅成像效应中的作用,得到了双光栅成像效应发生时,两个光栅的空间频率、衍射光级数以及光栅放置位置之间的关系式,这与实验所得结果相一致。     

基于平行平晶的三步相干衍射成像系统

传统单光束多强度重建(SBMIR)系统中,多次平移图像传感器所积累的误差导致光电成像系统的成像效果及有效分辨率降低,为了解决这一问题。本文提出基于平行平晶的三步相干衍射成像系统,采取插入或抽取2块平行平晶的方法获取3个不同的衍射面,实现了对复振幅型物体的成像及恢复重建。数值模拟及实验表明,系统有效克服了SBMIR系统中数次平移的误差积累问题,且仅需记录3个衍射面,避免过采样。而且光学系统实现简便、可重复性高。     

The spectral combination characteristic of grating and the bi-grating diffraction imaging effect

This paper reports on a new property of grating, namely spectral combination, and on bi-grating diffraction imaging that is based on spectral combination. The spectral combination characteristic of a grating is the capability of combining multiple light beams of different wavelengths incident from specific angles into a single beam. The bi-grating diffraction imaging is the formation of the image of an object with two gratings: the first grating disperses the multi-color light beams from the object and the second combines the dispersed light beams to form the image. We gave the conditions necessary for obtaining the spectral combination. We also presented the equations that relate the two gratings’ spatial frequencies, diffraction orders and positions necessary for obtaining the bi-grating diffraction imaging.     

Nanoscale imaging of buried structures with elemental specificity using resonant x-ray diffraction microscopy

We report the first demonstration of resonant x-ray diffraction microscopy for element specific imaging of buried structures with a pixel resolution of approximately 15 nm by exploiting the abrupt change in the scattering cross section near electronic resonances. We performed nondestructive and quantitative imaging of buried Bi structures inside a Si crystal by directly phasing coherent x-ray diffraction patterns acquired below and above the Bi M5 edge. We anticipate that resonant x-ray diffraction microscopy will be applied to element and chemical state specific imaging of a broad range of systems including magnetic materials, semiconductors, organic materials, biominerals, and biological specimens.     

On influence of collimating slit imperfections on the quality of experimental data in high-resolution x-ray diffraction

High-resolution x-ray diffraction and imaging techniques commonly assume a well-defined plane wave incident on the sample. Experimentally, the wave-front is limited by a collimating slit. Slit imperfections, such as surface roughness on the edges, may significantly contribute to the formation of the diffraction pattern from a specimen placed behind the slit. These effects become more profound when imaging at the nano-scale. This Letter presents experimental and simulated x-ray diffraction data quantitatively demonstrating the influence of slit edge imperfections on the formation of the diffraction pattern in the far-field regime.     

用菲涅耳理论研究衍射光路可逆性

 用菲涅耳衍射理论研究了光栅及双光栅成像系统衍射光路的可逆性。首先用菲涅耳衍射理论分析单片光栅衍射光的复振幅分布,根据其复振幅分布的相位关系研究其可逆性;再根据单片光栅衍射光路所具有的结论来分析双光栅衍射成像效应的衍射光路可逆性,得到了光栅衍射光路及双光栅成像系统光路具有部分可逆性;应用衍射光路的部分可逆性诠释了双光栅成像效应的本质及光栅的汇合光谱特性是色散光谱特性的逆效应,并根据衍射光路具有部分可逆性的特性实现了图像处理。     

Thermal light subwavelength diffraction using positive and negative correlations

Ghost imaging and diffraction, inspired by the Hanbury Brown and Twiss effect, have potential in both classical and quantum optics regimes on account of their nonlocal characteristics and subwavelength resolution capabil?ity, and therefore have aroused particular interest. By extending the correspondence imaging scheme, we utilize the positive and negative intensity correlations in diffraction and perform subwavelength diffraction with pseudo-thermal light. In the experiment, a subwavelength(A/2) resolution and a better signal-to-noise ratio(10.3% improvement) are simultaneously achieved. The scheme can be utilized as a complement to the existing ghost imaging scheme to improve image quality.     

基于大数值孔径环形光锥照明的超分辨光学 显微成像方法研究

提出和发展了一种基于大数值孔径环形光锥照明的远场超分辨光学显微成像新方法, 采用将发光二极管(LED)面光源、窄带滤光和环形光锥照明相结合的特种照明方式, 实现超分辨显微成像. 建立了大数值孔径环形光锥照明成像的物理模型, 根据标量衍射理论, 在不同环形光锥照明时, 推导出光学显微系统像面衍射斑光强分布的理论计算公式; 通过Matlab求解和绘图, 得到衍射斑光强的分布图样, 从理论上证明这一成像方法可以有效提高光学显微镜的分辨率; 建立了相应的显微成像系统, 通过实验验证了该方法可有效改善显微镜的成像质量, 显著提高分辨率; 在中心波长450 nm、环形光锥数值孔径1.125—1.25时, 实验获得的分辨率至少优于150 nm, 与理论研究结果相符合, 从而证明了这一方法的可行性.     

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.     

平面变线距光栅衍射场的解析表达式

利用多缝干涉原理计算了平面变线距光栅的衍射场分布,给出了它的主极大位置、半宽度等物理量.讨论了该光栅在成像参量变化时对光栅衍射场的影响,得到了变线距光栅单色器参量变化的限制范围.     

Coherent X-ray diffraction imaging of nanoengineered polymeric capsules

For the first time, nanoengineered polymeric capsules and their architecture have been studied with coherent X-ray diffraction imaging technique. The use of coherent X-ray diffraction imaging technique allowed us to analyze the samples immersed in a liquid. We report about the significant difference between polymeric capsule architectures under dry and liquid conditions.     

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.     

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。     

实验研究探测器大小与散焦长度对无透镜鬼衍射的影响

无透镜鬼衍射是一种特殊的非局域关联成像技术,通过对包含物体信息的测试光路和不含物体信息的参考光路的光场强度涨落关联进行测量,在参考光路上可得到物体的衍射图样。利用赝热光源实验研究了探测器尺寸大小和光路散焦长度对无透镜鬼衍射质量的影响。实验以四缝物体为例,定量研究了探测器大小和散焦是如何改变无透镜鬼衍射的成像结果,并和理论模拟进行了比较,获得了比较一致的结果。利用图像相关度定量分析了实验结果与理想无透镜鬼衍射图像的差别,发现这两者都会使无透镜鬼衍射的质量变差。