偏振干涉成像光谱仪中偏振化方向对调制度的影响

论述了自行研制的偏振干涉臧像光谱仪的原理,分析了其分光机理和成像原理;实在 重就起偏器、分析器的偏振化方向对干涉图调制度的影响进行了分析和计算,推导了偏振化方向偏离理想方向时调制度偏角的变化关系,给出和讨论了调制度随偏 角变化的空间曲面以及最大调制离（Ｖ＝１）和最小调制度（Ｖ＝０）时偏振器偏振化方向的空间取向。     

双功能数字散斑干涉位移及空间梯度同时测量

为了满足无损检测中复合材料在复杂载荷下多参数变量评估的需求,提出了一种基于光路复用的双功能数字散斑干涉系统,能够同时实现数字散斑干涉和数字剪切散斑干涉测量功能.通过控制其中一个反射镜-波片组合,当该组合离位时,构成数字散斑干涉测量光路,实现离面位移测量;当该组合在位时,构成数字剪切散斑干涉测量光路,实现离面位移空间梯度的测量.测量过程中只需简单切换该组合的位置就可以实现单次加载下被测物体表面离面位移及其空间梯度的同时测量.该系统光路结构简单、切换效率高,能够同时获得高质量的位移及空间梯度测量结果.实验证明,双功能数字散斑干涉系统既具备高抗干扰能力,又具备高灵敏度测试能力,适合复合材料无损检测现场使用.     

基于光学涡旋相移技术的离面位移测量

设计了基于光学涡旋相移技术的离面位移测量实验方案,实现了电子散斑干涉中相移的数字控制.该方法利用输入液晶空间光调制器中的叉形光栅产生涡旋光束,通过涡旋光束绕轴的旋转产生相移;同时,产生的涡旋光束又作为参考光与物光干涉.实验中,在物体发生离面位移前后依次输入四幅叉形光栅,产生相移步长为π/2的涡旋光束,利用CCD获得涡旋光与物光的干涉光场,从而获得离面位移场的包裹相位;再通过解包裹,获得物体离面变形的相位变化.光学涡旋相移法可应用于离面位移测量.     

光栅大错位数字散斑干涉术的研究

提出一种新的大借位数字散斑干涉术。它在成像物镜的像方空间放置光栅,利用光栅的衍射原理,使来自参考物和被测物的光波在像面发生干涉。用傅里叶光学原理详细讨论了该方法的基本原理,并对受均布载荷的周界固定方板这一典型试件的离面位移场进行了实测。结果表明,实验值和理论解吻合。报导了一些应用实例。理论和实验表明,该方法不仅具有全息干涉计量术达λ/4的高灵敏度,还具有防震要求低和能在明场环境下进行现场测量的显著优点。     

单边干涉图的数据处理方法研究

干涉成像光谱仪干涉图的采样方式一般有两种,即单边采样和双边采样,单边采样干涉图往往保留零光程差附近的部分“短双边”采样数据以利于数据处理.本文对空间调制干涉成像光谱仪不同干涉图采样方式下的光谱复原方法进行了研究,讨论了空间调制干涉成像光谱仪单边干涉图的切趾与相位修正,提出了更为合理和准确的方法.研究发现,合理设置短双边数据在减小仪器的原始数据量的同时,能够保证复原光谱的准确度.     

空间外差干涉光谱仪信噪比研究EI北大核心CSCD

以传统非成像式的高光谱空间外差干涉光谱仪为例,详细推导了传统空间外差干涉光谱仪的空域和光谱域信噪比(SNR)的表达式,分析了仪器各影响因素与SNR的关系,包含空间分辨率、光谱分辨率、干涉条纹调制度和电子学噪声等,并结合样机成像方式进行了讨论,得出了相应的结论。结果表明,计算SNR可有效评估和反映光谱仪的特性。     

二维光纤干涉理论

分析了由三根单模保偏光纤纤端出射光场的干涉特性,建立了二维光纤干涉的理论模型.在一级近似下,推导了二维光纤干涉光场场强分布的理论表达式.讨论了实现二维光纤干涉的相关条件,并用二维傅里叶变换方法,分析了干涉图的空间频谱特性.给出了相关实验结果.     

离焦散斑错位干涉术的逐点滤波分析与应用

通过相关计算,分析了离焦散斑错位干涉术的逐步滤波方法,得到了杨氏条纹的形成及分布特性。讨论了逐点滤波法的实用意义并给出了在缺陷检测中的应用实例。     

用于物体三维测量的光纤投影器的设计与数值模拟

新的光学三维传感和计量方法不断涌现,在这些测量方法中,结构光投影器的设计至关重要。将光纤引入其中,设计了多光纤空间编码面结构投影器,利用多光纤干涉可以在空间形成条形、方形、六角形等多种干涉图样,从而构成了多功能光纤干涉图像投影器,并对各种空间编码结构的投影图像给出了计算机仿真结果。讨论了投影器的空间编码结构参数对测量范围和测量精度的影响,以及与编码器结构相适应的测量方法。该研究对多光纤干涉图像投影器的设计制作与实际应用具有一定的参考意义。     

光源空间相干性的测量

时间相干性及空间相干性都是从发光本质来考虑产生干涉的条件对光源的要求.它们是光干涉现象中的重要概念.本文以典型的杨氏干涉实验讨论空间相干性的测量,以加深对空间相干性的理解.     

飞秒激光离焦抽运熔融石英产生超连续白光的实验研究

利用飞秒激光在熔融石英介质中传输产生能量达数毫焦、波长范围覆盖400-900 nm 且光谱分布较为均匀的超连续白光,实验过程中将熔融石英介质离焦放置以避免被击穿. 研究了入射激光能量以及介质离焦距离对超连续白光特性的影响. 结果表明采用高能量的入射激光脉冲离焦抽运介质的方法能够有效避免介质 击穿损伤并提高超连续白光脉冲的能量输出.     

A multiple focused probe approach for high intensity focused ultrasound based surgery

To produce deep-seated surgical lesions using ultrasound requires high power and intensity levels at the target sites. Conventionally, large transducers are used which require big apertures and so are generally suitable only for extra-corporeal access. Such transducers also result in strong off-focus maxima, where the resulting hot spots can destroy normal tissue whilst deep-seated large tissue volumes are being ablated. This paper describes a new approach in which it is proposed that multiple probes are used simultaneously, each at a relatively low power, to result in an overlapping focused region of high temperature without strong off-focus hot spots. Robotic techniques could be used to move the individual probes in coordination to sweep out the desired region of tissue ablation. Simulation and planning are the key to quality prediction for high intensity focused ultrasound (HIFU). Simplified two-dimensional and three-dimensional models of HIFU probes have been developed to study the characteristics of various multi-probe configurations. Preliminary simulation results show that the multi-probe system can be arranged successfully to minimise off-focus hot spots. Experimental results are presented which validate the modality and confirm this positive finding. Further prediction studies and planning will be necessary to achieve the most appropriate desired treatment, by varying the pulse duration and spacing.     

新型显微成像光谱仪系统中线阵针孔离焦研究

显微成像光谱仪技术是最近新兴的一种生物组织检测方法,它可以广泛应用在生物医学检测,疑难病症分析、预防、诊断中,已经成为当今生物组织检测领域研究的热点。提出了一种新型的基于线阵针孔阵列的激光扫描共焦显微成像光谱仪系统LP-LSCMIS方案,介绍了其工作原理及优点,讨论了该装置中线阵针孔阵列离焦对系统性能的影响,分析了离焦对生物组织荧光图像的光谱分辨和自体荧光光谱的调制深度的影响。推导出了光谱分辨和调制深度与离焦量的关系式。结果表明,离焦对仪器的性能有较大的影响,因此在装置装调时要求有更高精度的调整机构。     

多束高斯光束的相干叠加分析

采用Collins公式推导了入射高斯光束在输出场的场分布解析式，模拟了四束光在靶点相干叠加的强度分布，并分析了入射光束的位相差和离焦量对靶点光强分布的影响。     

Ground-state calculations of confined hydrogen molecule H2 using variational Monte Carlo method

The variational Monte Carlo method is used to evaluate the ground-state energy of a confined hydrogen molecule H₂. Accordingly, we considered the.me case of hydrogen molecule confined by a hard prolate spheroidal cavity when the nuclear positions are clamped at the foci (on-focus case). Also, the case of off-focus nuclei in which the two nuclei are not clamped to the foci is studied. This case provides flexibility for the treatment of the molecular properties by selecting an arbitrary size and shape for the confining spheroidal box. A simple chemical analysis concerning the catalytic role of enzyme is investigated. An accurate trial wave function depending on many variational parameters is used for this purpose. The obtained results for the case of clamped foci exhibit good accuracy compared with the high precision variational data presented previously. In the case of off-focus nuclei, an improvement is obtained with respect to the most recent uncorrelated results existing in the literature.     

Radially polarized LG01-mode Nd:YAG laser with annular pumping

We demonstrated a radially polarized, LG₀₁-mode Nd:YAG laser by applying annular-shaped pump light. The annular profile of the pump light was originated from the mode conversion inside a conventional multimode fiber under off-focus coupling condition. This laser gave a maximum output power of 1.2 W at 1,064 nm with a slope efficiency of 28.3 %.     

Three-dimensional tracking of fluorescent nanoparticles with subnanometer precision by use of off-focus imaging

We show that the position of a fluorescent nanoparticle can be measured in three dimensions with subnanometer precision and 100-ms temporal resolution by use of standard epifluorescence video imaging in off-focus mode. The particle can be tracked without feedback in a volume of at least 40 microm x 60 microm x 3 microm. With the technique presented, the structure-mobility relationship of 216-nm latex particle in a porous polymer network was studied in three dimensions.     

Joint transform correlator based on off-focus inputting and spherical wave illuminating power spectrum

An improved joint transform correlation technique is proposed for efficient multiple-target detection. The proposed technique employs off-focus inputting and spherical wave illuminating joint power spectrum to overcome false-target detection by eliminating the false correlation peaks while alleviating the effects of noise and other artifacts. Compared with the reported techniques, the proposed method does not need preprocessing for reference image and Fourier plane phase filtering, which makes the recognition process more suitable for all-optical setup to be realized. Thus the speed advantage of the recognition system is more prominent. Moreover, the proposed technique can maximize the utilization efficiency of the space-bandwidth product and the CCD by the new input method. The feasibility and effectiveness of the proposed method are demonstrated by numerical results.     

固体浸没透镜用于飞秒三维光存储研究

为进一步提高光存储密度，利用固体侵没透镜（SIL）与数值孔径为0.55的长工作距离物镜对飞秒激光脉冲进行聚焦，完成了PMMA及石英介质上的存储实验,并对聚焦物镜焦点与SIL底面离焦时的介质内焦点位置和系统的数值孔径进行了模拟。实验结果表明：当聚焦物镜焦点与SIL底面适当离焦时，实际聚焦在介质内的焦点深度不断加深，且系统的有效数值孔径不断增大。利用这一结果，在距PMMA表面20μm的地方得到了点间距1μm，层间距2.5μm的6层空间点阵；在距石英介质表面15μm的地方获得了点间距为0.6μm，层间距为2.5μm的5层空间点阵，其存储密度可达1.1×1012bits/cm3。     

Shadowgraph investigation of plasma shock wave evolution from Al target under 355-nm laser ablation

The propagation of a plasma shock wave generated from an Al target surface ablated by a nanosecond Nd:YAG laser operating at 355 nm in air is investigated at the different focusing positions of the laser beam by using a time-resolved shadowgraph imaging technique. The results show that in the case of a target surface set at the off-focus position, the condition of the focal point behind or in front of the target surface greatly influences the evolution of an Al plasma shock wave, and an ionization channel forms in the case of the focal point set in front of the target surface. Moreover, it is found that the shadowgraph with the evolution time around 100 ns shows that a protrusion appears at the front tip of the shock wave if the focal point is at the target surface. In addition, the calculated results of the expanding velocity of the shock wave front, the mass density, and pressure just behind the shock wave front are presented based on the shadowgraphs.