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。     

无狭缝一步彩虹全息的新方法

本文提出一种新的三维漫射物体的一步彩虹全息方法.该法是在曝光过程中将被摄物体与成像透镜同时沿垂直光轴方向移动,并通过场镜使合成狭缝直接成像在场镜后焦面上,可得到较大观察范围的无畸变彩虹全息像.     

透镜光轴上的光场分布

透镜作为一种特殊简单的二元衍射光学元件,推导计算了它带有硬边孔径光阑和高斯激光束入射情况下的光轴上光场复振幅分布的一段表达式,并对几种不同参数的高斯光束情况给出了具体计算结果.当高斯光波退化为平面波和透镜相对孔径较大时,它所描述的光轴上的场分布与《光学原理》.一书上的结果一致. 关键词：     

全息透镜的发展

<正> 由于全息术的发展和利用,出现了一种新型的成象元件,两个相干点源记录的全息图制成全息透镜。它的成象原理和制造工艺与普通透镜都不同。目前,国外在全息透镜的设计和制造方面进展较快,已经把全息透镜用于第三代夜视仪、     

相干点源照明时消球差光学系统的像场结构

利用矢量傅里叶变换和稳相法获得了相干点源位于光轴上任意位置时，消球差光学系统像场结构的积分表达式，详细研究了使用线偏振光照明时像平面上大物方孔径角对像场结构的影响.模拟计算表明，在像空间垂直于光轴的平面上，如果物方孔径角较大，磁场分布绕光轴旋转90°后不再与电场分布相同，电场能量密度、磁能量密度和玻印亭矢量分布的等高线始终近似为椭圆，并且物方孔径角是导致玻印亭矢量分布失去圆对称性的主要因素.同时当使用小像方孔径角时，电场能量密度分布形状的长轴方向垂直于物空间电场的振动方向；随着像方孔径角逐渐增大，电场能量密度分布形状的长轴方向将逐渐变为与物空间电场的振动方向相同.这些结论完全不同于以前理论所预测的结果. 关键词： 成像系统 像场结构 矢量傅里叶变换 稳相法     

消全息透镜色差的一种新方法

<正> 一、引言近年来,全息术的一个重要分支——全息光学元件(HOE)技术发展很快。国外已经把全息透镜应用于全息扫描器,全息头盔显示器等等。许多器件已经商品化。由于全息透镜是衍射元件,所以其色差是很严重的。为了减小色差,需用窄谱光源照明,限制了全息透镜的应用,国外许多学者都强调这一点。全息透镜是否能用于宽谱光源场合呢?70年代以来,国外一些学者在这方面进行了探讨,其中最吸引人的是J.N.Latta的工作。他运     

多狭缝空间滤波假彩色编码

利用空间滤波合成狭缝彩虹全息技术对二维透射物进行假彩色编码,当参考光以不同的方向传播时,记录二维透射物的不同空间频谱所对应的物像,全息图在白光再现时将透镜平移就呈现不同颜色全息效果图。     

“光学一题”解答

题中给出干涉条纹间距 与屏幕位置无关,这说明两相干点光源只能在无限远,即点光源S正位于透镜L的物方焦点上,这是解题的关键.可以肯定,透镜L右侧是传播方向夹β角的两束平行光的干涉场,且β=a/f’ 如图,依据制作全息光栅的原理。栅距　　　　　　　　参与相干的两束平行光传播方向之间夹角β的关系为“光学一题”解答@潘维济$南开大学     

一种光路自准方法

在光学实验中,经常遇到的一个课题是如何把各光学元件调节到它们的正确位置上,借助于机械轨道。经纬仪和可调焦平行光管等光学仪器进行位置调节是常用的方法.本文基于光栅在光路中的衍射作用和杨氏双缝干涉现象,提出了一种光路自准方法.它已成功地应用于光学Walsh变换[1]实验中.在这个实验中曾经设想和试用过多种调节手段。企图把各全息透镜调节到它们的正确位置上,由于调节仪器的光轴与实验光路的光轴很难保持一致,以致效果不甚理想.对于光路自准方法,调节光路就是实验光路,即在光路系统中传播的光波既是调节用光波又是实验用光波,二者是…     

高数值孔径聚焦三维光链的研究

通过设计衍射光学元件对入射矢量光进行调制，在高数值孔径聚焦系统焦点附近产生沿光轴方向的三维多点光俘获结构——光链.并针对不同的入射矢量偏振、聚焦透镜的数值孔径以及衍射光学元件结构，对光链性能的影响分别进行了系统的分析，实现对该独特光俘获结构的可控性研究. 关键词： 衍射光学元件 矢量光 光镊     

Fabrication and verification for the small-form-factor holographic optical pickup

In this investigation, a small-form-factor (SFF) pickup head with a holographic optical element (HOE) is fabricated. The system employs a finite-conjugate object lens to focus a light beam. A holographic optical element is used to simplify the optical configuration. It provides a better means of alignment of fabrication and reduces the size of system relative to reflective light route. Micro prisms are fastened with HOE and a silicon substrate, laser diode and photodiode are integrated into the optical system. The pickup head system based on discrete components and a flip chip bonder with highly accurate alignment was to integrate it. The micro holographic optical pickup head is fabricated and tested. Experimental results including the spot diameter and the focusing error signal (FES), demonstrate that the optical system is a feasible.     

Holographic distant display in dichromated gelatin

A transmission holographic optical element (HOE) has been manufactured, which changes the direction and divergence of light from a laser-illuminated transparent object, for example, a meter scale, so creating a virtual image a considerable distance from the viewer. The HOE is made in dichromated gelatin, with Ar laser light of wavelength 488 nm, and is reconstructed at 633 nm with a HeNe laser. Diffraction efficiency, luminance and contrast are measured at various points in the 16 X 16 cm² hologram. The visibility is good and there are modest distortions.     

High resolution digital holographic microscopy for the study of aggregated natural cellulose nanowhisker fibers

In this paper, digital holographic (DH) microscopy demonstrates its ability to perform a full characterization of nanofibers. The high resolution and magnification of the presented method to study the nanofibers are tested using standard MIL-STD-150A 1951 USAF resolution test target. In this investigation, aggregated natural cellulose nanowhisker fibers are positioned in the front of the microscopic objective using a 3D translation stage in the object arm of DH setup. The recorded off-axis holograms are refocused using the angular spectrum method. The reconstructed complex field is used to calculate optical phase and intensity distributions of the object at different reconstruction depths. A simple algorithm is used to define the focused image with suitable accuracy. The dimensions and orientation of the fibers can be evaluated from the optical field at different depths. Then, the shape and textures along the aggregated natural cellulose nanowhisker fiber can be presented in a 3D space.     

3-D airflow measurement using smoke particles

A new 3-D PIV-technique that is applicable to low velocity airflow in a real space such as indoor airflow is proposed, and its performance is inspected through a simulation and an experimental application. In this technique, two parallel planes separated by short distance are illuminated by a pair of laser light sheets of different colors. The visualized images are separated with optical filters, and recorded on VTRs. The 2-D tracer pattern movement on visualized planes is tracked with pattern tracking and the movement normal to the visualized planes is calculated from the difference of tracer concentration between two planes. The simulation result showed that the algorithm proposed here can calculate 3-D velocity field adequately, but the experimental result showed that the luminous intensity difference between two visualized planes became the main source of experimental errors.     

Non-contact scanning measurement utilizing a space mapping method

In this study, a novel approach to a measuring methodology and calibration method for an optical non-contact scanning probe system is proposed and verified by experiments. The optical probe consists of a line laser diode and two charge-coupled device (CCD) cameras and is placed on a computer numerical control (CNC) machine to measure the workpiece profiles. A space mapping method using the least-squares algorithm is presented for the probe calibration and profile measurement. This method provides a simple and accurate calculation of the relationship between the real space plane and its related image space plane in a CCD camera. A transparent grid with regularly spaced nodal points is used to construct the space mapping function. The space coordinate of an object can be obtained from its image in the CCD camera via the mapping function. The measured profile data are smoothed by the B-spline blending function and can be transferred to a CAD/CAM package for industrial applications. Experimental results show that this technique can determine the 3-D profile of an object with an accuracy of 60 μm.     

简化的三维体轮廓测量术

基于直接条纺位移分析的三维测量具有简单，快速，精确的特点，本给出了该方法的光学调制和计算机解调原理，以及用该方法进行简单三维测量的主要步骤。     

Robust optical systems for nondestructive testing based on laser diodes and diffractiveoptical elements

Two robust systems for vibration measurements are presented. Both systems are based on low-cost laser diodes. The stability of the optical systems is achieved by implementing the optical system as a holographic optical element (HOE) while using a common-path interferometer concept for the measurement scheme. The former system facilitates real-time simultaneous tracking of vibrations about two axes perpendicular to the optical axis. The latter system is an electronic speckle interferometer working in a differential mode providing whole-field information on the angular deformation about one axis between two states of the object. It will be argued that these concepts will provide compact, self-aligning systems for industrial use due to the inherent possibility of mass fabrication.     

基于光学三维形貌数字重建的不规则表面的参数测量

针对不规则形状物体表面参数测量困难的问题,提出了一种利用光学三维形貌数字重建技术来获取待测物体表面三维数字信息的方法。首先利用傅里叶变换得到反映三维物体表面高度的相位数据,在计算机中重建三维待测物体,然后再利用Matlab软件编写面向用户的人机交互界面,通过计算机鼠标指定待测量的表面区域,最后运用Matlab软件对鼠标所指定区域的三维数字信息进行处理,根据几何关系计算出指定区域的表面积、两点间的曲线长度等参数,实现人机交互式的非接触测量。