菲涅尔全息滤波光强相关识别的理论与实验依据

本文对用菲涅尔全息滤波器进行无透镜光强相关识别的问题重新进行了论证,结果再次证明菲涅尔全息滤波器完全可以用作相关识别。     

信息光学 全息术与器件

O438．1 2005021186 利用菲涅尔波带法计算三维全息=Study of CGH for 3D image using Fresnel zone[刊,中]／张晓洁(浙江大学现代 光学仪器国家重点实验室．浙江,杭州(310027)),刘旭… //光电工程．-2004,31(12)．-58-60,67 根据全息理论,从点光源菲涅尔全息图的计算出发, 提出一种利用主菲涅尔波带计算三维物体菲涅尔全息图 的方法。通过读取3DS文件直接获得三维物体表面各点     

菲涅尔数字全息的脉冲响应

数字全息是用CCD记录全息图并用计算机数值重建全息像的一种全息新方法.在数字全息中,通过对不同记录参数下记录的全息图的数值处理,可以消除零级光和共轭光,从而将数字全息系统看作是一个线性系统.本文依据全息理论和付里叶频谱分析,对菲涅尔数字全息系统的脉冲响应和分辨本领进行了理论分析.结果表明,在矩形等间隔抽样的情形下,菲涅尔数字全息的脉冲响应是由CCD有限大小的孔径衍射斑调制的矩形函数;菲涅尔数字全息的分辨率由CCD的孔径尺寸决定;由于CCD像素具有一定的大小,使得点光源的像发生弥散.     

菲涅尔透镜的线彗差及其在一步彩虹全息中的应用

本文叙述了菲涅尔透镜的一种新型象差——线彗差及这种象差的特性和其他象差的关系。薄平菲涅尔透镜是一步彩虹全息中较理想的成象透镜。     

菲涅尔菱体在确定1/4波片快慢轴中的应用

设计了一种新的测定 1/4波片快慢轴的实验。从菲涅尔公式出发 ,根据两次全反射后反射波和入射波各分量的位相变化 ,分析了菲涅尔菱体用于光的偏振态转换的相变理论 ,并提出利用菲涅尔菱体确定 1/4波片快慢轴的新方法。由于菲涅尔菱体的消色散作用 ,从而解决了通常测定 1/4波片快慢轴中的入射光波长受到限制的问题。     

单幅同轴全息图两步迭代收缩重建

利用压缩传感理论中的两步迭代收缩重建算法,开展单幅同轴全息图重建实验研究,实现单幅同轴全息图共轭重建像的消除并克服数字全息技术在轴向聚焦平面识别能力的不足。以数字图像和标准分辨率板为记录物体,比较分析了基于两步迭代收缩算法和菲涅尔近似衍射重建算法的重建质量;以两根裸光纤为实验样本,分析了两步迭代收缩重建算法对记录物体轴向不同焦平面的识别能力。实验结果表明两步迭代收缩重建算法可得到清晰度高于68.73%的重建信息,同时对直径为125 m的两根光纤在9 mm的轴向间距条件下,显示出了比全息菲涅尔近似算法更好的聚焦平面识别能力。这一轴向聚焦识别能力有助于数字全息技术应用于功能材料梯度参数或功能涂层光学器件涂层厚度检测。     

纯相位菲涅尔全息图的反馈迭代算法及其硅基液晶显示

研究了纯相位菲涅尔计算全息图的制作方法,给出了一种生成纯相位菲涅尔计算全息图的算法.首先研究了菲涅尔衍射的数值模拟算法,分析了两种数值模拟算法的计算速度.将计算速度较快的菲涅尔衍射数值模拟算法和迭代算法相结合,并引入比例反馈,得到纯相位菲涅尔计算全息图的反馈迭代算法.其次,对比例反馈系数的选取进行了实验研究,得到其最优经验值范围,然后进行了仿真实验.仿真结果表明,该算法降低了重构误差,提高了全息图重构质量.最后基于新型空间光调制器反射型硅基液晶,建立了全息显示光电实验系统,对该算法进行了验证.     

可编程菲涅耳相位透镜应用于多平面全息投影

研究了基于菲涅耳相位透镜实现多平面全息投影的方法,采用硅基液晶相位调制器建立了多平面全息投影系统.首先,利用可编程菲涅耳相位透镜代替傅里叶透镜,将计算机生成的相位全息图与菲涅耳透镜的相位结合;其次,基于时分复用和空分复用原理提出了加载菲涅耳相位透镜与相位全息图到相位空间光调制器上的两种方法;最后,讨论了在多平面全息投影中每个单一平面实现旋转物体动态360°视角显示的方法.实验结果表明:在距离硅基液晶分别为500、800、1 100和1 400mm处的四个重构平面可以获得全息投影图像;通过动态地改变菲涅耳相位透镜的焦距,可以实现多平面全息投影.     

像面照度均匀的环带式菲涅尔透镜设计

为了解决太阳光经传统菲涅尔聚光镜聚光后太阳能电池接收面上的光强分布不均匀问题,设计了一种环带式菲涅尔聚光镜。根据菲涅尔环带设计方法,把接收面划分为与之对应的环带,使光线在经过菲涅尔聚光镜的表面环带后进入相应的接受面环带,减少了光能损失并提高了光强分布均匀性。给出了在350 nm ~760 nm波段范围内太阳张角角度为0.54°、口径200 mm、高宽比为0.65、聚光比为400的菲涅尔聚光系统设计实例,通过Tracepro模拟并分析了菲涅尔聚光镜的光学能力。结果表明:在接收面尺寸相同的情况下与参数相同的的传统匀光菲涅尔聚光镜相比,此环带菲涅尔透镜光斑能量分布均匀性达到75%。     

复通菲涅耳光学相关滤波器

本文介绍了一种同区复通菲涅耳全息滤波器的制备方法,井基于此种滤波器实现了多个模式的光学相关识别。文中给出了同区复通菲涅耳全息滤波器的理论分析,并给出了相关识别的实验结果。     

Parallel Modified Signed-Digit Computing for Large-Scale Two Dimensional Data Array

We propose a novel parallel algorithm of modified signed-digit (MSD) computing, in which MSD digits are encoded to three bit plane (BP) patterns. The addition of two MSD data arrays is performed with two steps: calculating nine intermediate patterns from encoded BP patterns and calculating three BP patterns with the nine intermediate patterns. A system module constucted with nine beam splitter cubes is developed for optical demonstration. Preliminary experimental results are given.     

Concentric-Ring Patterns in a Helium Dielectric Barrier Discharge at Atmospheric Pressure

We perform the theoretical simulation of the concentric-ring patterns between two parallel electrodes covered with thin dielectric layers within the scope of a two-dimensional diffusion-drift model at atmospheric pressure. The time evolution of the discharge patterns is studied and the concentric-ring patterns with different radii shift alternately. The spatial-temporal evolution of electron density in a cycle at different time scales is performed.     

用MeF3金相显微镜研究LiNbO3晶体的光像

用MeF_3金相显微镜观察了多畴和单畴的LiNbO_3晶体的X、Y、Z切面的蚀像和光像.发现各切面光像形态与各切面的蚀像形态对应,并与晶体的对称性完全一致.利用晶体的光像确定晶体极性和晶轴是一种简便的光学方法.     

采用分离式差分标定靶的单摄像机标定方法

采用分离式差分标定方法实现对单摄像机的高精度标定。在摄像机的物面位置上放置多个小尺度的分离式标定靶,每个标定靶上有标准点阵列,对每个光点由高斯曲面拟合法得到其CCD像面上的位置,光点位置检测结果的稳定性(均方根)达到1μm(相当于CCD 0.0053 pixel)。利用同一标定靶上标准点之间的物面差分坐标,进行四次曲面拟合,建立摄像机的像面与物面之间的映射关系。该方法对各个标定靶之间的距离没有提出要求,采用多个小尺寸的差分标定靶代替整体式的大尺度标定靶,降低对大尺度标定靶的制作要求。实验表明,当各个标定靶之间的相对角度误差小于60″时,标定残差平均值可以达到4.8μm(相当于CCD 0.028 pixel)。     

Solution Lithography for Colloidal Crystal Patterning: Revisiting Flory–Huggins Interaction Parameters and Co-Nonsolvent Systems

For fundamental studies and practical applications, colloidal crystal patterns on substrates are typically fabricated through etching and conventional lithography. However, a wet-chemical based method is necessary for simplifying the procedure, preserving the substrate structure, and reproducibly fabricating the colloidal crystal patterns. The present study demonstrates that colloidal crystal patterns can be conveniently generated using thermodynamic relationships between a polymer colloid and surrounding solvents. Close-packed colloidal monolayers in good solvents that cause colloidal swelling spontaneously transform into non–close-packed crystal patterns when non-solvents that cause their shrinkage replace the good solvents. The colloid diameter in the close-packed monolayer decreases significantly when the polymer in the colloid is passing thermodynamic theta conditions (when Flory–Huggins interaction parameters increase to higher than ≈0.5). The close-packed monolayers also transform into the patterns in co-nonsolvent conditions. The “solution lithography” might be particularly useful for patterning colloids on curved microstructures and plastic/flexible films. The colloidal shapes in the patterns vary with the solvent pairs and substrates. The method does not require special facilities to reproducibly fabricate the patterns. The study further suggests methods simultaneously fixing the patterns. The patterns exhibit anti-reflection properties. Therefore, the solution lithography is applicable to optics, electronics, analytical science, and energy systems.     

Turing patterns beyond hexagons and stripes

The best known Turing patterns are composed of stripes or simple hexagonal arrangements of spots. Until recently, Turing patterns with other geometries have been observed only rarely. Here we present experimental studies and mathematical modeling of the formation and stability of hexagonal and square Turing superlattice patterns in a photosensitive reaction-diffusion system. The superlattices develop from initial conditions created by illuminating the system through a mask consisting of a simple hexagonal or square lattice with a wavelength close to a multiple of the intrinsic Turing pattern's wavelength. We show that interaction of the photochemical periodic forcing with the Turing instability generates multiple spatial harmonics of the forcing patterns. The harmonics situated within the Turing instability band survive after the illumination is switched off and form superlattices. The square superlattices are the first examples of time-independent square Turing patterns. We also demonstrate that in a system where the Turing band is slightly below criticality, spatially uniform internal or external oscillations can create oscillating square patterns.     

Pattern formation in a predator–prey model with spatial effect

In this paper, spatial dynamics in the Beddington–DeAngelis predator–prey model with self-diffusion and cross-diffusion is investigated. We analyze the linear stability and obtain the condition of Turing instability of this model. Moreover, we deduce the amplitude equations and determine the stability of different patterns. Numerical simulations show that this system exhibits complex dynamical behaviors. In the Turing space, we find three types of typical patterns. One is the coexistence of hexagon patterns and stripe patterns. The other two are hexagon patterns of different types. The obtained results well enrich the finding in predator–prey models with Beddington–DeAngelis functional response.     

多光束激光干涉光刻图样

利用电磁理论,研究了多光束激光干涉图样的产生原理,结合计算机数值模拟和相关实验结果,分析了干涉图样的影响因素.研究结果表明:多光束激光干涉图样可以看成是多组余弦分布的平行线条纹的叠加;相干光束的偏振方向、入射方向、光束间相位差是干涉图样的重要影响因素,改变这些因素,余弦分布的平行线条纹的振幅、位置、周期和方向发生变化,...     

一种无需标记的在线三维测量方法

提出了一种无需标记的物体在线三维面形测量方法。将一固定的正弦条纹投影到待测运动物体上,借助物体运动产生等效的相移变形条纹。基于傅里叶变换轮廓术的调制度对各帧变形条纹计算,提取其具有某一特定分布的特征区域,采用相关度最大法,检测各帧变形条纹对应的调制度特征区域的位移量来检测出物体的移动,从而实现像素匹配,得到一组像素坐标完全一一对应的等效相移变形条纹图。利用Stoilov相移算法得到物体的截断相位,利用位相展开算法展开位相,通过位相和高度映射即可实现在线移动物体的面形测量。通过计算机仿真验证了该方法的可行性。     

An improved stair phase encoding method for absolute phase retrieval

An improved phase unwrapping method is proposed to reduce the projection fringes in three-dimensional (3D) surface measurement. Color fringe patterns are generated by encoding with sinusoidal fringe and stair phase fringe patterns in red and blue channels. These color fringe patterns are projected onto the tested objects and then captured by a color CCD camera. The recorded fringe patterns are separated into their RGB components. Two groups of four-step phase-shifting fringe patterns are obtained. One group of the stripes are four sinusoidal patterns, which are used to determine the wrapped phase. The other group of stripes are four sinusoidal patterns with the codeword embedded into stair phase, whose stair changes are perfectly aligned with the 2π discontinuities of sinusoidal fringe phase, which are used to determine the fringe order for the phase unwrapping. The experimental results are analyzed and compared with those of the method in Zheng and Da (2012. Opt Express 20(22):24139–24150). The results show that the proposed method needs only four fringe patterns while having less error. It can effectively reduce the number of projection fringes and improve the measuring speed.