菲涅耳微透镜列阵衍射效率的测试

介绍了测量菲涅耳微透镜列阵的衍射效率的两种不同方法及其系统，方法简单易行，并实际测试了具有微小单元尺寸的菲涅耳微透镜列阵的衍射效率。     

菲涅尔型阵列光纤准直器的研究

菲涅尔透镜列阵，具有易阵列化的优点，设计中心波长相同的透镜列阵和中心波长不同的透镜列阵，并对由此列阵构成的准直器的光束耦合特征进行分析和计算，与通用的准直器的相关参数进行比较，表明菲涅尔透镜列阵在光束准直耦合中具有较高的耦合效率，可以用于制作阵列光纤准直器。     

微透镜列阵与红外探测器列阵集成芯片的研究

在分析微透镜列阵光聚能原理的基础上,针对背照式256290铂硅红外焦平面探测器列阵 的结构参数,设计了衍射微透镜列阵,使入射光通过硅基底聚焦至探测器的各个光敏面上, 提高光能利用率从而增强探测能力。实验获得了微透镜列阵与红外焦平面集成芯片,并在热成像中取得了良好的结果。     

一种新颖的超大点阵分束实现方法

首次提出了一种实现超大卢、阵光束分束的新方法，它是利用位相迭加原理和ＶＬＳＩ技术将光栅分束器和位相型菲涅耳微透镜列阵集成为一体，构成了一种新型的光束分束列阵器件—一菲涅耳计算机源生全息分来器（ＣＧＦＢＳ），以实现１２８×１２８，甚至更高卢、阵数的光点分束。     

原子层厚度菲涅尔波带片及其宽谱聚焦特性

基于菲涅尔波带片构型的平面衍射透镜在现代光学系统中发挥着重要的作用,是高端光学成像系统等应用的关键元器件之一.现有菲涅尔波带片结构多基于金属薄膜或高折射率电介质材料来制备,难以满足集成光电子系统可集成化的核心需求.本文提出一种基于原子层厚度二维材料的菲涅尔波带片结构,基于损耗辅助的相位调控机制,在原子层厚度的MoS2二...     

用于OCT动态聚焦的液晶菲涅尔波带透镜研究

提出了利用液晶菲涅尔波带透镜实现光学相干层析成像(OCT)动态聚焦的方法.根据扭曲相液晶空间光调制器(TN-LCSLM)的光学特性,设计了适用于OCT动态聚焦的菲涅耳波带透镜.利用TN-LCSLM型菲涅耳波带透镜进行了变焦控制实验,焦距实测结果与设计值比较吻合.此外,本文讨论了采用TN-LCSLM型菲涅耳波带透镜实施动态聚焦涉及到的一些问题.     

利用菲涅尔波带法计算三维全息

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的空间位置信息,模仿物理全息计算出点的菲涅尔图,将组成三维物体的各点的菲涅尔波带叠加从而获得三维物体的全息图。该方法区别于用菲涅尔衍射公式的传统全息计算,用加法运算代替指数、乘除运算,从而大大加快了计算输出全息图的速度,且具有信息连续、无冗余信息等特点。实验对由 1060 个采样点组成的物体进行全息计算,生成一幅 1024×768 的全息图,所需时间为 83s。     

衍射微透镜列阵掩模制作软件的设计

研究了衍射微透镜列阵的设计方法及ＣＩＦ格式掩模数据的数据结构与生成方法,设计了一套产用软件,采用图形切割、跟踪计算等方法,解决了生成子孔径为矩形、六 方形及圆环扇形的衍射微透镜列阵掩模的问题,满足了实际系统对衍射微透镜列阵子孔径形状的各种需求。     

主镜台阶数目对衍射成像系统传递函数的影响分析

为研究位相型菲涅尔透镜台阶近似引起的衍射杂散光对衍射成像系统调制传递函数(MTF)的影响,本文运用波动光学仿真分析方法模拟光波的传播。通过有限个级次的衍射波面在系统像面上相干叠加,得到系统的点扩散函数(PSF);对其进行傅里叶变换,得到系统的MTF。以菲涅尔主镜口径为80 mm的衍射成像系统为样机,分析了衍射主镜台阶数目为二、四、八时,系统MTF与理论设计值的差异。结果表明,随着衍射主镜台阶数目的增加,衍射杂散光对系统MTF的影响减小;并且四台阶时,与设计值的偏差已经小于0.5%。最后结合几何光线追迹仿真分析,提出将衍射主镜加工成中心区域多台阶、边缘部分为二台阶的思路,降低了衍射杂散光的影响。     

余弦-高斯光束通过光阑-透镜分离系统的焦移

利用Collins公式,研究了余弦-高斯光束通过光阑-透镜分离系统时的轴上光强分布和聚焦特性。研究表明轴上光强分布和相对焦移是光学系统参数、光束参数 、菲涅尔数和光阑尺寸的函数。通过选择适当的光学系统和光束参数,焦移现象消失或反转。     

Focal shift and the axial optical coordinate for high-aperture systems of finite Fresnel number

Analytic expressions are given for the on-axis intensity predicted by the Rayleigh-Sommerfeld and Kirchhoff diffraction integrals for a scalar optical system of high numerical aperture and finite value of Fresnel number. A definition of the axial optical coordinate is introduced that is valid for finite values of Fresnel number, for high-aperture systems, and for observation points distant from the focus. The focal shift effect is reexamined. For the case when the focal shift is small, explicit expressions are given for the focal shift and the axial peak in intensity.     

Theoretical and experimental investigations of the effect of diffractive multifocal focusing of radiation

The new optical effect of diffractive multifocal focusing of radiation, predicted earlier by theory, on a bicomponent diffraction system with small Fresnel numbers that consists of two plane screens with circular apertures on given optical axes, is confirmed experimentally. It is shown that the diffraction picture in the focal planes of such a system represents the circular nonlocal bands of the Fresnel zones with a bright narrow peak at the center, whose intensity in the experiment can exceed by six to ten times the value of the incident plane-wave intensity. Experimentally it is established that the diffractive multifocal focusing of radiation on real screens with axial circular apertures, whose diameters exceed the radiation wavelength, is insensitive to the rough external conditions: thickness of the screens, irregularities of the edges and nonideal form of the apertures, heterogeneity of the initial distribution of the incident-wave intensity, and changes in the medium of the wave propagation.     

Improved diffraction integral for studying the diffracted field of a spherical microlens

By introducing a new kind of Green function, we formulate an improved diffraction integral, which can be used to numerically evaluate the diffracted field of a microlens of plane-convex shape. Analytical expressions for the diffracted field of microlens are derived for the case where the curvature radius of the convex surface is larger than the dimension of the microlens aperture. The validity of the results and the diffracted field of the microlens are illustrated with numerical examples. The focal shifts of the diffracted field are found to depend mainly on the Fresnel number N of the microlens.     

White-light-modified Talbot array illuminator with a variable density of light spots

A flexible array illuminator, comprising only two conventional optical elements, with a variable density of bright white-light spots is presented. The key to our method is to obtain with a single diffractive lens an achromatic version of different fractional Talbot images, produced by free-space propagation, of the amplitude distribution at the back focal plane of a periodic refractive microlens array under a broadband point-source illumination. Some experimental results of our optical procedure are also shown.     

微透镜填充因子快速检测方法

本文提出了一种有效的微透镜阵列填充因子快速检测方法.文章从光的标量衍射理论出发,分析了连续浮雕微透镜阵列的衍射光斑分布与透镜子口径、透镜矢高之间的关系,推导出了微透镜阵列远场衍射光斑的理论模型,用该模型对不同填充因子的微透镜阵列为例进行计算机模拟分析,并且搭建了实验装置来获得实际的衍射光斑.结果表明,模拟光强分布与实际衍射光斑相当接近,在此基础上给出了微透镜衍射光斑分布与填充因子之间的半定量关系,为微透镜阵列的快速检测提供了一种有效手段.这种方法可以实现微透镜阵列的准确、简单、低成本的填充因子检测,极大地提高了生产效率,满足了实际测试的要求.     

Rigorous electromagnetic analysis of the common focusing characteristics of a cylindrical microlens with long focal depth and under multiwavelength illumination

The common focusing characteristics of a cylindrical microlens with a long focal depth and under a given multiple-wavelength illumination are analyzed based on the boundary element method (BEM). The surface-relief profile of a finite-substrate-thickness microlens with a long focal depth is presented. Its focusing performances, such as the common extended focal depth (CEFD), the spot size, and the diffraction efficiency, are numerically studied in the case of TE polarization. The results show that the CEFD of the microlens increases initially, reaches a peak value, and then decreases with increasing preset focal depth. Two modified profiles of a finite-substrate-thickness cylindrical microlens are proposed for enlarging the CEFD. The rigorous numerical results indicate that the modified surface-relief structures of a cylindrical microlens can successfully modulate the optical field distribution to achieve longer CEFD, higher transverse resolution, and higher diffraction efficiency simultaneously, compared with the prototypical microlens. These investigations may provide useful information for the design and application of micro-optical elements in various multiwavelength optical systems.     

Optical effect of diffractive multifocal focusing of radiation on a bicomponent diffraction system

It is shown for the first time, to our knowledge, that when a plane wave illuminates a certain type of bicomponent optical system, consisting of two plane screens with circular apertures on a given optical axis, a multifocal diffractive focusing effect can appear. Here the diffraction picture in the focal planes represents the circular nonlocal bands of the Fresnel zones with a bright narrow peak at the center, whose intensity can exceed by 6-10 times the value of the incident-wave intensity. The detected optical effect is observed across a wide range of wavelengths, lambda = 0.4-10(3) mum, and ratios of the aperture diameters d(1) >/= 2d(2) = 25-1000lambda, and it is also insensitive to changes in the medium of the wave propagation. For the large diameters of input holes, d(1) = 2d(2) > 100lambda, or for wavelengths in the radio-frequency region of the spectrum, the bicomponent diffraction system acts as a long-focus lens with a high-intensity Gaussian distribution of radiation, at times exceeding the initial intensity, persisting at large distances (z = 1-100 cm) from the diffraction system.     

Fresnel diffraction by a circular aperture with off-axis illumination and its use in deconvolution of microscope images

The Fresnel approximation for off-axis illumination of a circular aperture is reexamined. The point-spread function for an aberration-free system can be expressed in terms of redefined optical coordinates. An improved expression is given for contours of constant intensity in the focal plane. The variation in axial width of the focal spot with angle of offset is discussed. The predictions are compared with exact calculations of the Rayleigh-Sommerfeld diffraction integral. Limitations for application in deconvolution of microscope images formed with objectives of finite tube length are discussed.     

Gaussian imaging transformation for the paraxial Debye formulation of the focal region in a low-Fresnel-number optical system

The Debye formulation of focused fields has been systematically used to evaluate, for example, the point-spread function of an optical imaging system. According to this approximation, the focal wave field exhibits some symmetries about the geometrical focus. However, certain discrepancies arise when the Fresnel number, as viewed from focus, is close to unity. In that case, we should use the Kirchhoff formulation to evaluate accurately the three-dimensional amplitude distribution of the field in the focal region. We make some important remarks regarding both diffraction theories. In the end we demonstrate that, in the paraxial regime, given a defocused transverse pattern in the Debye approximation, it is possible to find a similar pattern but magnified and situated at another plane within the Kirchhoff theory. Moreover, we may evaluate this correspondence as the action of a virtual thin lens located at the focal plane and whose focus is situated at the axial point of the aperture plane. As a result, we give a geometrical interpretation of the focal-shift effect and present a brief comment on the problem of the best-focus location.