用多焦点全息透镜实现多重谱分数傅里叶变换

提出用多焦点全息透镜实现多重谱分数傅里叶变换.利用全息方法通过一次曝光制作出多焦点的全息透镜,分析了用此全息元件实现这种变换的条件,并在实验上实现了多重谱分数傅里叶变换. 实验结果表明这种变换方法简便可行,可广泛应用于多通道光学信息处理系统及多目标图像识别系统中.     

简单透镜作傅里叶变换透镜

本文从光学透镜的傅里叶变换特性,用P.w方法论述单透镜、双单透镜、双胶合透镜和正负分离透镜实现傅里叶变换透镜的可能性。     

用全息透镜记录多重分数傅里叶变换全息图

提出一种全息透镜记录多重分数傅里叶变换全息图的新方法，它能在三维空间不同位置和不同方向上分别再现所记录的多个物体的图象，分析了利用全息透镜记录多重分数傅里叶变换全息图的原理及特点，制作了多重分数傅里叶变换全息图，并获得了满意的再现结果。     

离散傅里叶方法分析环缝透镜产生无衍射光束

使用离散傅里叶方法分析环缝透镜系统产生无衍射(贝塞尔)光束。将基尔霍夫衍射积分公式与菲涅耳衍射积分公式转换成傅里叶变换的形式,在环缝透镜系统中用傅里叶方法描述观察面的光强分布,对衍射面进行数据抽样,导出观察面光强分布的离散化傅里叶公式;通过设置相关参数并使用MATLAB软件进行数值模拟,得到不同位置下的贝塞尔光强分布。设计环缝透镜系统进行实验验证,数值模拟和实验结果匹配度较高,表明离散傅里叶方法应用于环缝透镜系统是可行的。     

失调单球面折射系统的衍射积分和分数傅里叶变换

根据球面的几何特征，分析了单球面折射光学系统折射面倾斜和偏心时的失调特征；由失调元件矩阵和共轴元件矩阵的依次相乘，得到了完备的描述失调单球面折射光学系统的矩阵；从系统衍射积分与失调矩阵元的关系导出了该系统的失调衍射积分，并利用单球面折射光学系统的分数傅里叶变换结构参数得到了系统失调时的分数傅里叶变换结果.这些结果可用于数值计算和模拟该系统失调时对输入复振幅的衍射和分数傅里叶变换.     

用全息透镜组成傅里叶变换系统

本文将全息透镜作为一般的傅里叶变换元件,组成傅里叶交换系统,进行了相关运算以及模糊图象处理等实验.结果表明,对全息透镜傅里叶变换系统进行某些光学信息处理工作是可行的.     

用变形全息透镜实现变形分数傅里叶变换

利用一发散点光源和一束倾斜平行光制作出在两个垂直方向上具有不同焦距的变形全息透镜,且用此全息元件实现了变形分数傅里叶变换。变形全息透镜两个方向上的焦距随全息记录条件和再现条件而变化,分析了用这种全息透镜实现变形分数傅里叶变换的条件。实验表明,用该元件能够方便地实现任意级次的变形分数傅里叶变换。     

全对称傅里叶透镜的设计

本文研究了傅里叶透镜的设计,并叙述了一种对称型傅里时变换透镜.在相对孔径1:10时,输入面和频谱面处的象质均较好.傅里叶交换透镜的特点是必须对两对物象共轭位置(即位于前焦面处的输入面和位于后焦面处的频谱面)控制除畸变以外的全部象差.1969年后开始出现的傅里叶变换透镜,多属6～8片的对称或近似对称的四组元双远距型,本文叙述了一种严格对称型四片傅里叶交换透镜.     

数字无透镜傅里叶变换全息术中非傍轴及离焦像差的校正

对数字无透镜傅里叶变换全息图直接采用逆傅里叶变换进行物场的数值重建时.需要满足两个条件:第一,全息图的记录过程必须满足傍轴近似条件,否则再现过程中会产生非傍轴像差;第二,记录全息图时物平面与参考点光源到全息图记录平面的距离必须相等,否则再现过程中会产生离焦像差.理论分析了非傍轴及离焦记录条件下数字无透镜傅里叶变换全息图的灰度分布特点,并提出了相应的非傍轴及离焦像差的数值校正方法.根据实际的非傍轴或离焦记录情况.分别给所记录的数字全息图灰度分布矩阵乘以适当的非傍轴或离焦校正因子,以消除灰度矩阵中非傍轴或离焦因素的影响.然后再对校正后的伞息图灰度矩阵做逆傅里叶变换处理.即可得到准确的数字再现像.实验结果表明.该数值重建方法能够有效地消除无透镜傅里叶变换全息术中数字再现像的非傍轴像差及离焦像差,提高再现像的质量.     

无透镜傅里叶变换显微数字全息成像系统的焦深

基于透镜相干光学成像系统的斯特列尔(Strehl)判据, 对无透镜傅里叶变换显微数字全息成像系统的焦深进行了推导, 得到了参考点源对称偏置和非对称偏置两种情况下的焦深表达式. 结果表明, 无透镜傅里叶变换显微数字全息成像系统的焦深决定因素与透镜相干成像系统的焦深决定因素不同, 其焦深不仅与照明光源的波长, 成像系统的孔径及记录距离有关, 还与参考光源的配置有关. 计算机模拟和实验结果均证明了理论分析的正确性.     

Propagation characteristics of Bessel-like beams through ABCD optical system

Based on the Collins diffraction integral formula, this work focus to the study of the propagation properties of a Bessel-like beam through an ABCD optical system. As it is not easy to develop an analytical expression describing the transformation of the Bessel-like beams by an ABCD optical system, numerical integration method was indispensable to conduct this research. The characteristics of the transformation of Bessel-like beams by three optical systems: free space, Fourier transform, Fractional Fourier transform system and quadratic graded-index system are numerically examined and treated as examples of optical systems in this investigation. Some numerical results are carried-out to show how the superposition of multiple Airy beams propagates and transforms by an ABCD optical system.     

傅里叶变换系统的光线矩阵分析方法

本文应用光线矩阵方法,分析一般的非对称系统,导出了该系统的傅里叶变换条件;考虑到定位误差,文中给出了计算夫琅和费和傅里叶变换有效区域和物理焦深区的公式;并得出了在不同波面入射光波的情况下,谱面移动量的计算公式,最后给出了二个应用实例。     

平面屏系统中标量光波传播的矩阵理论(柱坐标)

本文在文献[8]的基础上,提出了一个平面屏系统中标量光波传播的矩阵理论。由于采用的是柱坐标系,所以它主要适宜于具有理想轴对称性的系统。它的主要优点,是较便于处理上述系统中某些用已有理论实际上较难处理的光传播问题。本文中未考虑散射屏。这个理论的适用范围是:系统中所有平面屏都垂直光传播轴;可对每一屏的衍射应用本文的衍射公式和近似条件;在反射、吸收和增益屏上的入射光锥角较小等。作为应用的例子,本文得出和讨论了无源光学谐振腔中振荡模的矩阵方程。把它和已有的Fox和Li的积分方程作了比较,表明了矩阵方程具有某些重要的实际优点。 关键词：     

求解分数傅里叶变换衍射积分的一种快速算法

在对Lohmann 二型分数傅里叶变换(FRT)和菲涅耳衍射积分进行比较的基础上,给出基于快速傅里叶变换(FFT)求解该分数傅里叶变换和菲涅耳衍射积分的快速算法及算法适用范围.数值模拟实验证明了理论的可靠性和算法的高效性.此快速算法为分数傅里叶变换在工程实际中的进一步广泛应用奠定了基础.     

阿达玛变换光谱仪狭缝衍射的编码修正

根据阿达玛变换光谱仪的原理与狭缝衍射特性,分析了光谱仪入射狭缝衍射对阿达玛变换光谱仪测量结果造成影响,对衍射情况下的阿达玛变换光谱仪的仪器结构矩阵进行了研究,得出了衍射情况下阿达玛变换光谱仪的编/解码方法,通过对入射光谱的还原分析,验证了编码/解码的正确性。该方法对阿达玛变换光谱仪的高精度光谱测量具有重要意义。     

碳酸钙在水溶性甲壳素溶液中的结晶行为

依据生物矿化基本原理,以甲壳素作为有机基质,探讨了在不同浓度甲壳素溶液中CaCO3晶体的生长情况;同时研究了生长体系的pH值和温度对生成CaCO₃晶体的影响。通过傅里叶红外光谱、扫描电子显微镜进行表征的结果表明,甲壳素溶液中形成的CaCO₃晶体完全不同于纯水中形成的晶体;而且甲壳素溶液的浓度不同,形成的CaCO₃晶体的晶型也有较大差别。在CaCO₃结晶过程中,CaCO₃对甲壳素也有影响,即晶体与甲壳素之间存在相互作用。     

Atomic structures by direct transform of diffraction patterns

We propose all the diffraction patterns can be directly transformed to provide three-dimensional atomic structures for the system studied. Depending on the scattering process, either the holography or Patterson transform scheme is used. For diffraction patterns which are generated from a localized emitter source or dominated by an inelastic-scattering feature like core-level photoelectron or low-energy Kikuchi electron, holography transform is needed. On the other hand, for diffraction patterns which were dominated by elastic-scattering, like grazing-incidence X-ray diffraction, electron correlated thermal diffuse scattering or low-energy electron diffraction curves, Patterson transform is needed. To prove our point, high-fidelity and artifact-free three-dimensional atomic structures obtained by transform of low-energy Kikuchi electron patterns and low-energy electron diffraction curves are presented. The future of these direct methods by transforming diffraction patterns will be discussed.     

Color-image encryption scheme based on channel fusion and spherical diffraction

A secure encryption scheme for color images based on channel fusion and spherical diffraction is proposed in this paper. In the proposed encryption scheme, a channel fusion technology based on the discrete wavelet transformation is used to transform color images into single-channel grayscale images, firstly. In the process of transformation, the hyperchaotic system is used to permutate and diffuse the information of red—green—blue (RGB) channels to reduce the correlation of channels. Then the fused image is encrypted by spherical diffraction transform. Finally, the complex-valued diffraction result is decomposed into two real parts by the improved equal module decomposition, which are the ciphertext and the private key. Compared with the traditional color image encryption schemes that encrypt RGB channels separately, the proposed scheme is highly secure and robust.     

Why to synthesize vaterite polymorph of calcium carbonate on the cellulose matrix via sonochemistry process?

Vaterite is an important biomedical material due to its features such as high specific surface area, high solubility, high dispersion, and small specific gravity. The purposes of this article were to explore the growth mechanism of vaterite on the cellulose matrix via sonochmistry process. In the work reported herein, the influences of experimental parameters on the polymorph of calcium carbonate were investigated in detail. The calcium carbonate crystals on the cellulose matrix were characterized by means of X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). Experimental results revealed that all the reactants, solvent, and synthesis method played an important role in the polymorph of calcium carbonate. The pure phase of vaterite polymorph was obtained using Na₂CO₃ as reactant in ethylene glycol on the cellulose matrix via sonochmistry process. Based on the experimental results, one can conclude that the synthesis of vaterite polymorph is a system process.