部分相干场的计算

本文描述:应用归化点扩散函数来计算最佳焦点处的Strehl强度及应用部分相干光成象理论来计算不透明直边和一对直线的亮度分布.结论是部分相干光象的极限分辨率是相干度的函数(除了象差).     

关于n平面线性相干光处理系统的讨论(Ⅰ)

讨论n平面线性相干光处理系统(简称n平面线性系统)的一般性质。在两个特例情况下,借助于傅里叶变换的相似性定理和空间频率的标度变换,可以证明:n平面线性系统的(n—1)个间距参数{z_i}_n-1不是实质性参数。利用所得结果,演示了相干光成象和空域中的频率的标度变换,说明理论结果是有效的。 关键词：     

非相干光三维成象

本文综述了非相干光三维成象的现状,其中包括横断面层析技术,波带片编码和随机点编码等。     

用成象自由度评价光学系统的信息量

本文探讨了一般光学系统的成象自由度传递及信息量问题,计算了不同信噪比σ₀/σ_n下一维相干光和非相干光照明的衍射受限系统的有效自由度数N_off,并与经典分辨率理论的象素数作了比较。     

利用非相干光成象方法制备低频全息光栅的技术和装置

本文提出的利用非相干光成象方法制备低频全息光栅的技术，是利用原始光栅在非相干光成象系统中产生的正、负一级衍射光波在象平面的叠加来实现光栅的记录，有效地抑制了相干噪音，降低了对环境条件的要求，并具有操作简便、装置简单和价格低廉等优点．这种方法适于制作频率范围为每毫米数十至数百条线的光栅．用这种方法制作的光栅已在一些领域中得到了较为满意的应用．     

染料分子电子激发态振动失相过程的非相干光时延四波混频研究

本文对噁嗪(Oxagine)、甲酚紫(cresyl violet)染料分子的吸收带和吸收边进行了非相干光时延四波混频(TDFWM-IL)的详细研究,得到了有关失相参量的数据,并利用非相干光时延四渡混频的多能理论解释了实验结果和失相参量的物理意义。     

空间频率彩色编码在遥感图象处理中的应用

空间频率彩色编码的方法是基于傅里叶光学中的空间滤波技术.关于相干光照明下的空间滤波方法在图象处理上的应用已为大家所熟知[1].这种方法对图象增强有明显作用,其主要缺点是:(1)由于用激光作光源,往往带来难以避免的相干噪声,严重地影响了成象质量.(2)无论用哪种滤波器,在突出某部分信息的同时,往往丢失了其他信息,故处理后的图象有时失去了原图的形象.空间频率彩色编码避免了上述缺点. 一、空间频率彩色编码方法及其发展 此方法所用光路基本上和相干光4f系统类似,只是用产生白光的溴钨灯S及一小孔W作为点光源,以代替激光.光经透镜L0准…     

部分相干厄米-高斯光束杨氏实验中的光强分布

将杨氏干涉实验作为双缝衍射现象处理,以部分相干厄米-高斯(H-G)光束为例,研究分析了多模部分相干光的杨氏双缝干涉光强和干涉条纹可见度的空间分布。数值计算说明,多模部分相干光束的空间相干参数、模阶数和缝遮拦比对衍射场中光强的空间分布(干涉花样)都有影响。当多模部分相干光的阶数为奇数时,轴上光强与光束的相干性会出现相消干涉;当多模部分相干光的阶数为偶数时,轴上光强与光束的相干性会出现相长干涉等。     

一种新的成象技术——穆斯堡尔成象

穆斯堡尔成象技术是1987 年由美国国家标准局S.J.Norton首先提出的[1].它与X射线成象(又称为CT断层成象)、核磁共振成象(NMR)一样能给出立体图象,虽然现在还不能在医学中应用,但在材料科学研究方面却已显示出广泛的应用前景. 在介绍穆斯堡尔成象之前,先介绍一下NMR成象.由于穆斯堡尔成象与NMR成象都依赖于原子核共振效应,因此它们具有许多相同的特征.NMR成象的原理是:由于原子核共振频率正比于局域磁场强度,因此,当施加一个外磁场于自旋体系时,不同频率的信号对应于实验样品内不同的空间位置.用这种方法可以将不同频率的信号转变为…     

部分相干光在大气湍流中水平传输路径上的展宽与漂移

基于部分相干高斯谢尔模型(GSM)光束在强湍流中的光束扩展半径,利用Andrews和Philips经典漂移方差模型推导了部分相干光在中强弱大气湍流中水平传输的漂移方差表达式,讨论了部分相干光在中、强、弱大气湍流中的展宽和漂移特性。结果表明:部分相干光的光束扩展受湍流的影响比受完全相干光的影响要小,初始半径越小的光束受到湍流的影响越大。短距离传输时,不同波长引起的光束漂移差别很小,且随着初始光束半径的增大这种差别随之减小。传输距离大于2km时,中强湍流中光束漂移均与波长有关且强湍流区漂移量较为明显。传输距离在10km内,光束空间相干长度大于0.005m时,光源空间相干长度对漂移的影响很小。     

Wide-field fluorescence sectioning with hybrid speckle and uniform-illumination microscopy

We describe a method of obtaining optical sectioning with a standard wide-field fluorescence microscope. The method involves acquiring two images, one with nonuniform illumination (in our case, speckle) and another with uniform illumination (in our case, randomized speckle). An evaluation of the local contrast in the speckle-illumination image provides an optically sectioned image with low resolution. This is complemented with high-resolution information obtained from the uniform-illumination image. A fusion of both images leads to a full resolution image that is optically sectioned across all spatial frequencies. This hybrid illumination method is fast, robust, and generalizable to a variety of illumination and imaging configurations.     

An Investigation of the Temporal Dark-Image-Sticking Phenomenon in an AC Plasma Display Panel With an Auxiliary Electrode

In this paper, the temporal dark-image-sticking phenomenon in an ac plasma display panel (PDP) with an auxiliary electrode is investigated. To investigate this phenomenon, temporal behaviors of a black background image were observed in accordance with the sustain-discharge time and the relaxation time. Since dark image sticking is related to the reset discharge, our measurements focused on the reset period. In the case of an ac PDP with three electrodes, iterant sustain discharges induced an increase in black luminance, thereby leaving a residual image. However, in the case of an ac PDP with an auxiliary electrode, there was no variation of luminance between the states before and after the iterant sustain discharges. As a result, no residual image remained, and no distortion of the image could be recognized with the human eye, even after iterant sustain discharges.      

3-D distortion of observed images reconstructed from a cylindrical holographic stereogram. (1) laser light reconstruction type

In the case that the image reconstructed from a cylindrical holographic stereogram with laser light reconstruction (LCHS) is observed by binocular vision, the 3-D distortion characteristics of the image are studied. Using an object of a distinctive construction, some examples are calculated and experimental results are also shown, and the optimum condition to synthesize the LCHS is given.     

Solar image recovery with a weak filling of the spectral plane by the method of projections onto convex sets

This paper is devoted to the problem of solar image recovery in synthesizing radio brightness maps in the case of an incomplete filling of the spectral region (the Fourier data are bounded by a cone with an angle much smaller than 180 deg.) The image was recovered by the method of projection onto closed convex sets (PCCS). Brief theoretical postulates which formed the basis for this method are presented. A comparative characteristic with the CLEAN method is given. The results of using this method for the model data and real data (recovery of the solar radio image obtained in the knife-edge beams of the SSRT) are presented.     

光电图像光照不均蜕化的校正及阈值分割方法*

分析了CCD获取的图像光照不均蜕化产生原因.针对光照不均蜕化的印刷电路板图像的具体情况,用同态滤波器在频域空间进行滤波而增强图像,从而改善图像的目标与背景对比度.讨论了最大类间方差法,给出了其优点.为了更好的分割图像,在此基础上,考虑两类间距与各类内聚性对图像分割的不同影响,提出了一种改进的最大类间方差法.最后对光照不均蜕化的PCB光电图像用不同方法进行了实验,结果表明改进方法能更好地分割图像.     

Photoelectron diffraction imaging for C2H2 and C2H4 chemisorbed on Si(100) reveals a new bonding configuration

A new adsorption site for adsorbed acetylene on Si(100) is observed by photoelectron imaging based on the holographic principle. The diffraction effects in the carbon 1s angle-resolved photoemission are inverted (including the small-cone method) to obtain an image of the atom's neighboring carbon. The chemisorbed acetylene molecule is bonded to four silicon surface atoms. In contrast to the C2H2 case, the image for adsorbed C2H4 shows it bonded to two Si surface atoms.     

PCB光电图像光照不均蜕化的校正及阈值分割方法

分析了CCD获取的图像光照不均蜕化产生原因.针对光照不均蜕化的印刷电路板图像的具体情况,用同态滤波器在频域空间进行滤波而增强图像,从而改善图像的目标与背景对比度.讨论了最大类间方差法,给出了其优点.为了更好的分割图像,在此基础上,考虑两类间距与各类内聚性对图像分割的不同影响,提出了一种改进的最大类间方差法.最后对光照不均蜕化的PCB光电图像用不同方法进行了实验,结果表明改进方法能更好地分割图像.     

Principles for radiation of time-harmonic elementary current in magnetized electron plasma half-space

The radiation emitted by a time-harmonic elementary current in magnetized electron plasma half-space, bounded by an ideal electric plane, is investigated using an exact formulation. It is found that: conventional image principle holds for vertical magnetization case; while for parallel magnetization case, coupled image principle seems to be valid.     

Log-polar transform-based wavelet-modified maximum average correlation height filter for distortion-invariant target recognition

In this paper, we report a log-polar transform-based filter for in-plane rotation and scale-invariant target recognition. The log-polar transform is a known space-invariant image representation used in several image vision systems to eliminate the effects of scale and rotation in an image. In case of in-plane rotation invariance, peaks shift horizontally, while in case of scale invariance, peaks shift vertically. For full out-of-plane rotation-invariance (0–360°), log-polar transformed images are used to train the wavelet-modified maximum average correlation height (WaveMACH) filter. Correlation peak height and peak-to-sidelobe ratio have been calculated as metrics of goodness of the log-polar transform-based WaveMACH filter. This filter would reduce the memory requirement for filter storage in a practical system. Simulation results have been presented.