铌酸锶钡晶体的光存储实验研究

通过全息存储光路调整,采用适当的曝光时间,在铌酸锶钡晶体中得到清晰的全息存储图象,并通过高压固化存储图象,测得全息存储时间衰减曲线.     

大容量体全息相关器存储时序的改进

体全息相关器的存储时序直接影响多通道输出的衍射效率均匀性,进而影响识别率。通过引入约束因子β,对传统的递减曝光时序进行改进,提出约束递减曝光时序,并用此时序在2400幅的存储容量下,实现了衍射效率较均匀的并行相关输出。     

光折变晶体均匀多重全息图存储研究

本文推导了光折变晶体角度编码多重全息存储中写入均匀光栅时的曝光时间递推公式.分析了散射效应对光栅写入时间常数的影响和写入光耦合对光栅振幅的影响,给出了两种因素影响下曝光时间计算的修正递推公式.数值计算结果表明,按照这种修正公式计算所得多重存储中各幅全息光栅振幅不仅均匀性好,而且振幅相对较大,这种曝光方法有利于提高晶体的存储容量.实验中以递推公式所得时间进行曝光记录,在厚度为0.6mm的Fe:LiNbO₃晶体中采用角度编码很容易存储了30幅全息图.     

高时间分辨的扫描式分幅技术

介绍了二种用于ICF激光等离子体诊断的X射线扫描式分幅技术的技术原理;分析了相关的性能参量.借助于特别设计的扫描变象管进行了该技术的原理性实验,并利用计算机数字图象处理技术进行图象的重构.实验获得了持续时间约100ps的发光过程的16幅图象,曝光时间优于10ps.阴极上空间分辨率分别为3.5lp/mm.     

微通道板选通X射线皮秒分幅相机

本文报道的超高速摄影机可在1.2ns内连续拍摄12幅图象,每幅图象的曝光时间为100ps,空间分辨率201p/mm,它具有几何畸变小、动态范围大等特点。对MCP皮秒选通的数值模拟考虑了电子渡越时间及弥散影响。变象管研制着重解决了微通道板上微带线的欧姆损耗问题。     

四通道X射线MCP行波选通分幅相机

简述了MCP行波选通分幅相机的工作原理及技术指标,报道了最新研制的四通道行波选通分幅相机的研制结果及使用情况,相机可接连拍摄12幅图象,每幅象的曝光时间为60至100ps、空间分辨率15lp/mm时调制度10％,观测时间在几百皮秒至几纳秒内可调.在星光装置上的使用表明相机的实用性强、抗干扰能力高,并在国内首次较全面地测量了各种靶型的时间分辨分幅结果.     

微通道板选通X射线皮秒分幅相机曝光时间的均匀设计

将均匀设计法应用于微通道板选通X射线皮秒分幅相机(MCP－XPFC)曝光时间的研究工作中,目的是找到一个简单高效的试验预估方法来指导分幅相机的研制和试验工作.基于分幅相机皮秒动态选通理论模型,建立了采用0.5 mm厚、长径比40的MCP的皮秒分幅相机选通脉冲参量与曝光时间之间的快速预估模型.利用这一模型得出了相机的曝光时间随选通脉冲脉宽和幅值分别呈抛物线变化,且脉宽和幅值对曝光时间具有交互影响作用.在试验参量范围内,此预估模型能够精确地代替相机理论模型和高效地指导实验.通过实验验证了预估模型,并分析了影响结果的因素.     

C.变象管高速摄影的最新进展

本文简要介绍和评述了在第十九届国际高速摄影与光子学会议上发表的有关变象管高速摄影技术的结果,据报道,飞秒条纹变象管的时间分辨率设计值达50fs,皮秒分幅相机的最短曝光时间实验值为50ps。CCD两维图象读出系统已普遍用于皮秒条纹相机系统。纳秒分幅/扫描摄影向高性能、程控化发展。本文还涉及了超短光脉冲技术的新成果在变象管动态测试中的应用。     

超高速分幅相机曝光时间测量的误差分析

基于超高速光电分幅相机曝光的控制原理,从光纤切割精度和激光器精确同步两个主要影响因素出发,讨论了采用超快激光脉冲和光纤阵列形成光延时结合CCD相机的方法测量高速相机曝光时间的误差,并提出了降低误差的技术措施。分析表明,光纤切割精度和激光器精确同步引入的误差仅为皮秒级,对纳秒级的相机曝光时间测量的影响可以忽略。采用光纤束阵列法,实验测量了超高速光电分幅相机的曝光时间,对比测量值与标称值,二者吻合良好,验证了此方法的有效性。     

Silex-I飞秒激光装置X射线探测系统时间特性北大核心CSCD

在Silex-Ⅰ飞秒激光装置上,利用32fs、800nm的激光辐照平面金靶,产生小于1ps的X射线脉冲,作为δ脉冲X射线源,研究XRD探测器的时间响应特性,并且探索X射线条纹相机时间分辨和分幅相机曝光时间的X射线标定方法。实验给出了XRD探测器的时间响应特性。解决了条纹相机和分幅相机触发晃动问题,给出了条纹相机时间分辨和分幅相机曝光时间的X射线标定方法,初步给出条纹相机时间分辨和分幅相机曝光时间。     

全息立体多重像的拍摄

本文介绍了用光栅对参考光进行调制,从而拍得全息立体多重像的方法。     

记录光强变化对光折变晶体多重存储衍射效率均匀性的影响

光折变晶体多重存储中,为获得均匀的衍射效率,要根据记录晶体的时间常数计算相继写入全息图的曝光时间,而晶体的时间常数是记录光强的幂函数.本文分析了光强变化对衍射效率的影响.结果表明,对曝光时间加以适当修正,可补偿光强变化对衍射效率均匀性的影响.     

Study on the simplified phase-shifting digital holographic microscopy

In this paper, a new simplified technique for effectively eliminating the zero order and the conjugate virtual image in digital holographic microcopy, which makes use of two-step phase-shifting method of just recording two holograms and an intensity image of object wave, is proposed. Meanwhile, combined with the principle of making full use of spatial bandwidth of the CCD sensor by in-line lens-less Fourier holographic recording geometry, the theory and experimental methods to increase the resolution of the reconstructed image in digital holography by using phase-shifting technique are detailedly analyzed. At end, the validity and availability of this technique has been demonstrated through the off-axis and in-line Fourier transform recording geometry. The study provides some theoretical and experimental guidance for the design and operation of a digital holographic microscopy system.     

三维漫射体单波长真彩色彩虹全息术

提出一种新的三维漫反射物体真彩色彩虹全息术,在普通一步法真彩色彩虹全息术的基础上,用单波长激光逆光路再现,可在同一种记录介质上一次曝光记录三维物体的真彩色全息图.因而特别适合于制作光致抗蚀剂模压全息母板.     

Localized holographic recording in doubly doped lithium niobate

Persistent holograms are recorded locally with red light in a LiNbO>(3) crystal doped with Mg and Fe. Selective erasure is realized by use of a focused UV sensitizing light. We demonstrate the recording of 50 localized images as well as selective erasure in a 4 mm x 4 mm x 4 mm crystal. A comparison of the total recording time for M holograms obtained with the conventional distributed-volume recording and the localized methods is presented.     

Computer-interferometric holograms used for laser beam scanners

We present a new technique to record holograms and its application to holographic laser beam scanners. “Computer-interferometric holograms” (CIH) are recorded interferometrically, one small facet at a time, and under computer control. Constructing scanner holograms by this technique allows for flexibility in the scan path, previously only achieved by computer-generated holograms (CGH). Experiments, demonstrating the useful application of the CIH recording technique to volume holograms, are described in a subsequent paper.     

Incremental holographic recording in lithium niobate with active phase locking

Angular-multiplexed hologram recording in iron-doped lithium niobate crystals was carried out with near-infrared light. An incremental recording schedule with active phase locking of the light pattern onto the hologram was used. Continuous and reproducible recording of holograms of equal efficiency was achieved, and a hologram multiplexing number, M/#=2 , for a 5-mm-thick crystal was obtained at a 760-nm wavelength of light.     

Wave front reconstruction of Fresnel off-axis holograms with compensation of aberrations by means of phase-shifting digital holography

Off-axis holograms recorded with a CCD camera are numerically reconstructed in amplitude by calculating through the Fresnel–Kirchhoff integral. A phase-shifting Mach–Zehnder interferometer is used for recording four-quadrature phase-shifted off-axis holograms. The basic principle of this technique and its experimental verification are described. We show that the application of this algorithm allows for the suppression of the zero order of diffraction and of the twin image and that the contrast of the reconstructed images can be further enhanced by digital compensation of the aberrations introduced by the holographic recording system     

Microscopic imaging and holography with hard X-rays using Fresnel zone-plates

The imaging properties of a Fresnel zone-plate (FZP) were used for magnified imaging of microobjects using hard X-rays. The experiments were done using 14 keV synchrotron radiation. The coherence properties of the radiation produced by an undulator allowed the recording of real images and holograms from an object in one single exposure. These images result from the positive and the negative first order diffracted beams respectively. The X-ray microscope worked at an X-ray magnification factor of 12 and could resolve structures of 0.3 μm in size. By going to slightly defocused conditions we obtained magnified images of the holographical nearfield diffraction pattern (in-line holograms) of the object.