激光聚变靶丸球度测量与评定

为了解决激光聚变靶丸表面形貌高精度测量与评定的难题,提出一种激光差动共焦靶丸球度测量与评定方法,该方法利用激光差动共焦测量系统的轴向响应曲线的过零点与其物镜焦点位置相对应这一特性实现对靶丸表面的定焦,通过将靶丸在两个正交的方向上分别旋转,测量并获取靶丸表面的数个截面,实现靶丸表面全形貌测量,利用最小区域球度评定算法,建立靶丸球度评定的三维模型,对靶丸表面形貌进行定量评定。搭建实验装置对靶丸表面进行采样测量,评定结果显示,该方法的测量重复性为0.15μm,为靶丸表面形貌测量与评定提供了一种可行方案。     

用于惯性约束聚变靶丸测量的激光差动共焦传感器

针对目前原子力显微镜等方法只能测量激光惯性约束核聚变(ICF)靶丸外表面等难题,研制了高精度、非接触、小型化的激光差动共焦传感器(LDCS).该传感器基于差动共焦原理,利用激光差动共焦轴向响应曲线的零点对靶丸内外表面和球心分别进行定位,并结合物镜微位移驱动技术,实现靶丸内外表面和壳层厚度的高精度测量.该方法减少了靶丸表面的反射率、倾斜等因素对测量瞄准特性的影响,显著提高了系统的抗干扰能力.将传统的显微成像与差动共焦测量光路进行有机融合,实现了对被测样品的精确瞄准.初步实验与理论分析表明:当测量物镜的数值孔径NA为0.65时,LDCS的轴向分辨力优于5 nm,信噪比优于1 160,过零点的标准偏差为10 nm.该传感器为激光惯性约束核聚变靶丸测量提供了一种新的技术途径.     

激光聚变靶丸内表面轮廓测量系统的研制

针对激光聚变靶丸内表面轮廓高精度无损测量的迫切需求,研制了一套激光聚变靶丸内表面轮廓测量系统。该系统通过最小二乘算法(LSC)计算出靶丸回转偏心量,并利用偏心调整台对靶丸偏心进行自动快速调整;然后,系统软件控制气浮回转轴承驱动靶丸旋转,利用激光差动共焦传感器(LDCS)轴向响应曲线过零点及光线追迹算法精确计算出靶丸内表面轮廓上每个采样点的几何位置;最后,对靶丸内轮廓测量数据进行LSC评定得到其圆度信息。实验证明,靶丸回转偏心的自动调整时间可达22s,当采样点分别为1 024,2 048及4 096时,靶丸内轮廓测量时间分别可达10,20及40s,且圆度测量标准差可达19nm(1 024点)。该系统实现了靶丸回转偏心的自动快速调整及其内轮廓的高精度、无损、快速、自动测量。     

激光 ICF 聚变靶丸轮廓测量系统标定方法

针对激光惯性约束聚变靶丸轮廓高精度测量系统的溯源标定问题,提出一种基于激光差动共焦测量原理的标定溯源方法。该方法基于激光差动共焦靶丸测量系统轴向响应曲线过零点精确对应测量系统焦点的性质,首先利用激光差动共焦靶丸测量系统测量经中国计量科学研究院计量检定的标准椭圆块的圆度,其次通过比对测量值和标准椭圆块圆度计量值,得出该系统测量传递系数为1.03,最后通过多次检定验证测量的方法,完成系统的高精度标定。实验结果显示,利用标定完成的系统进行激光聚变靶金属球比对测量,其标准差为37 nm,该标定方法的测量重复性为17 nm,其为靶丸表面轮廓的高精度测量奠定了坚实基础。     

基于卡尔曼预测的差动共焦轮廓跟踪测量方法

针对轴向扫描式差动共焦测量法(ASDCM)测量轮廓效率低下问题,提出一种基于卡尔曼预测的差动共焦轮廓跟踪测量方法。该方法使用激光差动共焦轴向响应曲线数百纳米量程的线性区间实现了表面连续轮廓高精度线性传感测量,提高了测量效率;同时引入基于卡尔曼预测器的轮廓跟踪原理利用已测轮廓点数据对未测表面预测并跟踪,扩展了线性传感轮廓测量法测量范围。实验结果表明,该方法相对于ASDCM法测量效率提升了8倍,且实现了轮廓PV值大于线性传感测量范围的标准椭圆柱高精度跟踪测量,激光聚变靶丸内轮廓圆度重复测量标准差达3 nm。为精密元器件表面连续轮廓的高精度、快速、无损测量提供了一种高质量方法。     

基于激光扫描和SFM的非同步点云三维重构方法

室外场景具有测量数据量大、扫描数据易重叠及建筑物表面信息复杂等特点,单靠激光扫描方法能够获得场景精确的深度信息,但缺乏颜色和纹理信息,利用从运动中恢复结构(SFM)方法可获得丰富的彩色信息,但重构精度不高,若将两种设备固定进行在线实时同步测量,易受到测量环境和系统制约不易实现。针对此问题,提出了一种基于激光扫描和SFM结合的非同步点云数据融合的三维重构方法。首先,提出利用手动选择控制点进行7自由度初始配准,再利用迭代最近点(ICP)算法对初始配准结果进行精确配准,最后利用最近点搜索算法将分布在经基于面片的多视图立体视觉(PMVS)算法优化后的SFM数据中的颜色信息与激光扫描的点云坐标进行融合。实验结果和数据分析显示,本文的方法能有效地将激光扫描与SFM点云数据进行融合,实现了室外大场景的三维彩色重构。     

基于分形和高斯滤波的维修件粗糙表面重构与基准提取

通过维修件粗糙表面轮廓的功率谱探讨了维修件粗糙表面的分形特征,利用W_M函数建立二维和三维粗糙表面分形模型,对维修件粗糙表面轮廓进行了二维和三维重构。并采用高斯函数,对利用分形模型所重构的粗糙表面进行滤波,分别提取了维修件粗糙表面分形模型的评定基准线和评定基准面。论文把分形理论和高斯滤波相结合,应用于维修件的粗糙表面的重构和评定,最后编写MATLAB程序,进行了实验仿真,为研究维修件表面微观几何形貌对结合面摩擦、密封等装配后的连接性能提供了基础。     

On the influence of imaging conditions and algorithms on the quantification of surface topography

The influence of the microscopical magnification resulting in different voxel size and shape and of the algorithm on parameters used for the quantification of the surface topography is studied using topographical images obtained by confocal laser scanning microscopy. Fracture surfaces and wire‐eroded surfaces of steel were used as samples. The values obtained for the global topometry parameters normalized surface area, mean profile segment length and fractal dimension depend with different degrees on the microscopic magnification and on the algorithm used to compute these values. The topometry values can only be used to establish correlations between the topography and materials properties and for the modelling of surface generating processes if the imaging and computing details are given.     

A method for the evaluation of thousands of automated 3D stem cell segmentations

There is no segmentation method that performs perfectly with any dataset in comparison to human segmentation. Evaluation procedures for segmentation algorithms become critical for their selection. The problems associated with segmentation performance evaluations and visual verification of segmentation results are exaggerated when dealing with thousands of three‐dimensional (3D) image volumes because of the amount of computation and manual inputs needed. We address the problem of evaluating 3D segmentation performance when segmentation is applied to thousands of confocal microscopy images (z‐stacks). Our approach is to incorporate experimental imaging and geometrical criteria, and map them into computationally efficient segmentation algorithms that can be applied to a very large number of z‐stacks. This is an alternative approach to considering existing segmentation methods and evaluating most state‐of‐the‐art algorithms. We designed a methodology for 3D segmentation performance characterization that consists of design, evaluation and verification steps. The characterization integrates manual inputs from projected surrogate ‘ground truth’ of statistically representative samples and from visual inspection into the evaluation. The novelty of the methodology lies in (1) designing candidate segmentation algorithms by mapping imaging and geometrical criteria into algorithmic steps, and constructing plausible segmentation algorithms with respect to the order of algorithmic steps and their parameters, (2) evaluating segmentation accuracy using samples drawn from probability distribution estimates of candidate segmentations and (3) minimizing human labour needed to create surrogate ‘truth’ by approximating z‐stack segmentations with 2D contours from three orthogonal z‐stack projections and by developing visual verification tools. We demonstrate the methodology by applying it to a dataset of 1253 mesenchymal stem cells. The cells reside on 10 different types of biomaterial scaffolds, and are stained for actin and nucleus yielding 128 460 image frames (on average, 125 cells/scaffold × 10 scaffold types × 2 stains × 51 frames/cell). After constructing and evaluating six candidates of 3D segmentation algorithms, the most accurate 3D segmentation algorithm achieved an average precision of 0.82 and an accuracy of 0.84 as measured by the Dice similarity index where values greater than 0.7 indicate a good spatial overlap. A probability of segmentation success was 0.85 based on visual verification, and a computation time was 42.3 h to process all z‐stacks. While the most accurate segmentation technique was 4.2 times slower than the second most accurate algorithm, it consumed on average 9.65 times less memory per z‐stack segmentation.     

三维光电振动测量技术的校准方法研究

为了分析三维光电振动测量仪测量的三维数据准确性,提出了一种利用标准小球做相对校准的简便方法。组成三维光电振动测量仪的5台激光测振仪发出的5束激光同时经过1个透镜,聚焦在位于透镜焦点处且安装在振动源上的标准小球球面上,软件处理小球振动时的三维分量,并与小球3个正交方向放置的3台激光测振仪测得的数据对比。通过微调小球的摆放位置,测量小球不同振动方向的三维振动信息,最后对数据进行误差分析,测量结果验证了该校准方法的可行性和适用性。     

Statistic optics discussion on the formula of digital holographic 3D surface profiling measurement

Based on the theories of statistic optics and scalar diffraction, this paper derived the digital holography formula for 3D object surface profile measurement. The results indicate that random changes of the scattering light phase will cause error in measurement when the detected object surface is optically rough. Moreover, more precise calculation formula should theoretically be used in case of there is a short distance between the CCD and the measured object, both for a smooth object and an optically rough object.     

一种基于机器人的曲面测量、建模和加工方法

提出了一种基于机器人的卷曲类自由曲面的测最、建模和加T路径生成方法.本文采用结构光测量方法设计了一种基于机器人的自动测量系统,实现了自由曲面零件的表面测量.根据测量数据和零件的形状特点提出了一种新的建模方法,该方法首先采用提出的截面法直接提取点云的边界,然后利用射线与局部拟合曲面的交点获得有序的精整数据点,实现了NURBS曲面的精确拟合.最后,对重构的自由曲面采用等参数线法生成了加工路径.实际的算例和应用验证了本文方法的有效性和精确性.