激光差动共焦透镜中心厚度测量系统的研制

基于高精度光学共焦定位技术研制了一种全新的非接触透镜中心厚度测量系统,该系统利用差动共焦技术的高轴向层析特性和轴向响应曲线的绝对零点对被测透镜的前表面顶点和后表面顶点分别进行精密瞄准定位;同时,利用激光干涉仪获得透镜前、后表面顶点的位置坐标;然后通过光线追迹算法计算透镜中心厚度,进而实现了透镜中心厚度的高精度非接触测量。实验结果表明,该系统测量精度高,测量标准差小于1μm,满足透镜中心厚度测量的精度要求。     

激光差动共焦曲率半径测量系统的研制

针对国内高精度曲率半径计量需求,研制一套激光差动共焦曲率半径测量系统.该系统采用差动共焦定焦技术,利用轴向光强响应曲线的过零点精确对应物镜聚焦焦点这一特性,借助过零点对被测件的猫眼和共焦位置进行精密瞄准定位,通过干涉测长技术获取两点间的距离,继而实现曲率半径的高精度测量.该测量系统的机电控制由主控软件完成,可实现机电扫描、数据采集及数据处理,自动化程度高.实验证明,该系统定焦灵敏度高,受环境波动影响小,测量精度可达3×10-6,满足了高精度曲率半径的计量需求.     

一种可控曲面光栅的研制

提出了一种制作曲面变间距光栅的方法。首先在平面基片上制作光栅,然后通过一种高分子材料(PDMS)作为载体将光栅转移到曲面上,而事先涂在曲面上的混合溶胶-凝胶取代了传统的光刻胶,使得光栅的制作效率大大提高。采用这种方法在曲率半径为100 mm的凹球面基底上制作了平均线密度为80 l/mm的光栅,并用环境扫描电镜以及数字图像处理法检测了光栅的线密度分布。检测结果表明:光栅质量好,条纹清楚,衍射效率也没有降低。所制曲面光栅具有平面光栅和透镜两种光学器件的功能,可用曲面变间距光栅一种光学元件取代透镜和平面光栅两种光学元件,简化了光路,提高了制作效率,降低了成本。     

脉冲激光波长测试系统光学天线研究

针对光纤光谱仪常规光纤探头接收面积小,难以探测远距离脉冲激光波长的情况,本文提出用带有光学天线的光纤光谱仪对脉冲激光幅度和波长进行测试的整体技术方案.通过对望远系统、光纤光锥、反射光锥等光学天线的接收角及光学增益进行的大量实验.结果表明采用不同的光学天线,可增大接收角或光学增益,实际应用中可以根据具体需要选择不同的光学天线.     

激光差动共焦透镜中心偏测量系统设计与实现

针对国内外透镜中心偏高精度测量的迫切需求,研制了一套激光差动共焦透镜中心偏测量系统。该系统从中心偏非接触测量的核心定焦原理入手,结合激光差动共焦定焦技术,解决了清晰度法定焦精度差的难题。在光学测量系统误差分析的基础上,对系统再次优化设计,并利用差动共焦轴向光强响应曲线过零点的位置与被测镜猫眼和共焦点精确对应这一特性,实现了透镜中心偏的高精度测量。通过实验表明,该系统测量精度为0.49%,与传统的清晰度法定焦测量相比,透镜中心偏的测量精度有效提高了6倍。该系统将差动共焦定焦技术有效的应用于透镜中心偏测量中,提高了被测镜猫眼和共焦位置的定焦能力,实现了高精度测量系统的设计,在光学测试和透镜加工及装配领域具有广阔的应用前景。     

High accuracy microdimension measurement system by using laser and CCD

A microdimension measurement system, using one-dimensional CCD as the sensor, was developed for measuring thin wire or slit. The principle of measurement is based on Fraunhofer's diffraction. The system performs data processing of the diffraction pattern by using filtering and curve-fitting, by which the measuring accuracy was extremely improved. The measuring range of this system is from 20 μm to 200 μm. The total measuring uncertainty is less than 0.04 μm and the repeatability of measurements is less than 0.011 μm. Moreover, experimental results indicate that the system is applicable to vibrating objects as well.     

单光源双光路激光并行共焦测量系统设计

针对传统激光并行共焦测量过程中存在的泰伯效应,提出将数字微镜器件（DMD）引入激光并行共焦测量系统来正确辨识正焦面的位置。采用了DMD作为光分束器件,从理论上验证了它是一种投影式的阵列光源,对激光分束后不会在光路方向上产生泰伯像;同时,考虑DMD不能对分束后的光线产生会聚作用,并非高效的并行光源分束器件,本文将DMD与微透镜阵列(MLA)结合构建了单光源双光路并行共焦测量系统。该系统利用DMD光路探测正焦面位置,利用微透镜阵列光路进行精确的共焦测量。实验结果表明,两种光路下的正焦面位置仅相差2 μm,在一个泰伯间距范围之内,可以较好地克服泰伯效应对激光并行共焦测量的影响,进而保证较高精度的并行共焦测量。     

An efficient way of convection heat transfer measurement on a curved surface

Accurate determination of convective heat transfer coefficients on complex surfaces with high spatial resolution is essential in the design and analysis of thermal systems. This study focuses on the implementation of a recently developed true color image-processing technique for the quantitative interpretation of liquid crystal images obtained from a curved surface. The interpretation includes the use of a linear hue versus temperature relation as an accurate temperature measuring tool, a color image analysis system and a transient heat transfer model for the conversion of time accurate temperature information into heat transfer coefficient maps. A square to rectangular transition duct is used as a heat transfer model representative of a curved geometry. The transient heat transfer experiments are performed with ambient temperature air in the transition duct model which is preheated by a custom designed electric heater. The measurements are performed on the curved bottom surface of the transition duct. Two dimensional surface distributions of heat transfer coefficient on the curved surface are presented with high spatial resolution. The hue-capturing technique provides extremely fine details of heat transfer coefficient when compared to other conventional discrete sensor methods. The technique is a highly automated heat transfer measurement method which reduces lengthy data reduction processes and significantly improves spatial resolution.     

基于连续扫描方式的激光共焦扫描显微镜的研制

研发了一套基于连续扫描的激光共焦扫描显微镜(laser confocal scanning microscopy,LCSM)系统。该系统采用工作台连续运动方式实现扫描,提出了利用单次采集的数据滤除随机噪声的方法,避免了多帧取平均对成像速度造成的影响。实现连续扫描的关键在于解决工作台运动与数据采集的同步问题,利用采集卡有限采集模式,合理匹配工作台参数和采集参数,成功解决了这一问题。详细介绍了影响分辨率的因素,通过合理选取探测器针孔直径,取样间隔,确保了实现高分辨率的要求。系统利用Visual C#开发的控制平台,成功地对生物细胞进行了扫描成像。实验结果表明:基于连续扫描的LCSM具有较高的分辨率,生成的显微图像没有任何畸变,并且成像速度有了大幅度提高。     

High-precision detection of focal position on a curved surface for laser processing

A new technique for detecting the focal position of a curved surface provides several advantages both in research and industrial applications. The quality of patterns lasered on a roll surface is determined by the precision of the focus detection, and surfaces of the massive rolls used in laser fabrication can be difficult to adjust properly using conventional technologies. Here, a unique method for detecting the focal position of a curved surface based on the reflected profile of a laser beam is presented. The versatility of the proposed technique results from being able to adjust the laser beam based on changes in the shape and diameter of the beam spot when the specimen surface deviates from the focal plane. A theoretical model based on three-axis movement is proposed, and experimental setups are developed based on the model. Analysis of the obtained results enables high precision positioning of the specimen and identification of the focal point. Furthermore, the presented technique can be used to locate the focal point on any curved surface. Therefore, the theoretical model, analysis results, and focal detection method can be combined in an algorithm for a novel auto-focusing system that can be applied to laser processing of curved surfaces, such as fabricating microgrooves, or engraving roll surfaces in printed electronics.     

基于液晶的激光偏振测量系统研究

主要研究基于液晶的激光偏振测量系统,利用液晶可变相位延迟器(LCVR)代替传统测量技术中的旋转波片,改变所加的电压值控制液晶双折射系数,对入射光的偏振状态进行精确控制.通过偏振光调制法测量斯托克斯(Stokes)参量,从而实时、准确地测量激光的偏振特性.同时,利用虚拟仪器LabVIEW软件平台实现系统的数据分析、处理、界面显示和打印输出功能的一体化.研究表明:该方法能够准确地测量光束的偏振特性,能够服务于从科研实验室到工业生产过程的各类应用领域,具有广阔的应用前景.     

Profile measurement of a wide-area resist surface using a multi-ball cantilever system

In the semiconductor industry, a device that can measure the surface profile of thin film like photoresist with high accuracy and high speed is needed. Since the surface of photoresist is very smooth and deformable, a device is required that will measure vertically with nanometer resolution and not damage the film during the measurement. We developed an apparatus using a multi-ball cantilever and white light interferometer to measure the surface profile of thin film. However, this system, as assessed with a scanning method, suffers from the presence of a moving stage and systematic sensor errors. Therefore, this paper describes an approach using a multi-ball cantilever as coupled distance sensors together with an autocollimator as an additional angle measuring device, which has the potential for self-calibration of a multi-ball cantilever. Using this method, we constructed an experimental apparatus and made measurements on resist film. The results demonstrated the feasibility of the constructed multi-ball cantilever system with the autocollimator for measuring thin film with high accuracy.     

Adjustment of the nanosecond laser pulse duration by using a carbon nanotube suspension

It is shown that the scanning of an optical cell with an aqueous suspension of carbon nanotubes along the optical axis of a focused laser beam leads to a smooth change in the duration of nanosecond laser pulses transmitted through the suspension. Pulses shorten owing to the pulse trailing edge cutoff, when the cell approaches the beam waist. In experiments, pulses of a YAG:Nd³⁺ laser with passive Q-switching and duration of 16 ns were continuously controlled in the range 16–10 ns.     

基于偏心抑制的激光差动共焦焦距高精度测量方法

针对测量球面透镜焦距过程中存在偏心误差导致测量光轴与透镜实际轴线不重合的问题,提出了一种基于偏心抑制的 激光差动共焦焦距高精度测量方法,通过驱动工作台旋转测得透镜偏心误差的大小及方向,实现了对被测透镜的误差采集;通 过分析误差大小及方向驱动姿态调整电机,消除了测量过程中由于存在偏心误差对焦距测量精度产生的影响;通过构建系统, 优化系统参数,实现了激光差动共焦焦距高精度测量;最终实现基于偏心抑制的焦距高精度测量,解决了焦距测量时测量光轴 与透镜实际轴线不重合从而对测量结果产生影响的问题。 基于该系统进行了焦距测量实验,实验表明:测量焦距为 100 mm 透 镜时,该方法相对重复测量精度(RMS)可达到 0. 000 503% 。 该方法显著提高了焦距测量的精度及重复测量精度,为焦距的精 密测量提供了一种有效的途径。 同时,该方法可应用到镜组加工与装配中,提高镜组的成像质量与测量精度。     

基于共焦法的透镜厚度测量系统设计

研究通过分析共焦法检测透镜厚度的原理,并结合实际,给出了共焦光学系统的设计指标及要求,据此设计了一套共焦光学系统,结合光纤、耦合器、光谱仪等设备构成了基于共焦原理的透镜厚度测量系统。文中分析了本共焦光学系统的公差,分析结果表明,所给公差相对较宽松,整个光学系统设计合理,且在此公差下,本光学系统仍能清晰成像。本系统的测量范围至少为15 mm,可以有较广泛的应用。对于普通的K9玻璃,本检测系统的测量范围可达23.4 mm,测量精度为1μm。     

集成激光位移传感器和编码器的曲面仿形测头研究

为实现对大量程自由曲面的高精度仿形测量,提出了一种利用闭环运动控制技术集成激光位移器和线性编码器的新方法。采用线性编码器和精密线性机构以及运动控制卡组成Z向位移量伺服随动系统,步进电机自动调整激光位移传感器位置使其工作在中心范围(95～105mm)内,线性机构位移量可由线性编码器测量得到,自由曲面的起伏变化可通过激光位移传感器和线性编码器的输出而得到。与激光位移传感器进行了线性度、示值误差以及重复性等精度参数对比实验,结果表明系统在扩大测量范围的同时具备较高的测量精度。     

Surface investigations on HgBr2 single crystals by using confocal scanning laser microscopy

A confocal scanning laser microscope operating at 514 and 488 nm has been used to obtain two-dimensional (2-D) images of the mercuric bromide (HgBr2) crystal surface by photoluminescence, reflection, and transmission phenomena. Our measurements indicate that regions showing a strong photoluminescence may appear on the surface. By processing the 2-D images. we obtained the three-dimensional images, which offer a better possibility for the investigation. The analysis of spectral lines may be correlated with the presence of the Hg impurities.     

Rapid measurement of surface roughness for face-milling aluminum using laser scattering and the Taguchi method

In this paper, an experimental model for the rapid measurement of surface roughness (R_rms) in CNC face-milling specimens using the laser speckle method and digital image processing is established. The specimens used in this study were made of 6061-aluminum alloys through the high-speed face-milling process. In order to evaluate the effect of machining conditions, such as the feed rate, the spindle speed, the depth of cut, and the material of the cutting tool on the roughness of the specimens, the Taguchi method was used to determine the optimal parameters for machining. The laser radiation results in the speckle structure formed in the space when coherent light is scattered through an optically rough surface. The features of the speckles depend on the characteristics of the rough surfaces. Hence, the experimental work for the roughness measurement is based on the speckle effect. The experimental setup in this study consisted of a He-Ne laser, a ground glass, a CCD camera, and a digital image processing system developed using the Virtual Basic language. Computer evaluation of the speckle images revealed the values of R_rms rapidly. This study proposed a precise and non-contact optical method for evaluating the surface roughness from 0.20 to 0.60 μm.