Industrial computed tomography (CT) is widely used in the measurement field owing to its advantages such as non-contact and high precision. To obtain accurate size parameters, fitting parameters can be obtained rapidly by processing volume data in the form of point clouds. However, due to factors such as artifacts in the CT reconstruction process, many abnormal interference points exist in the point clouds obtained after segmentation. The classic least squares algorithm is easily affected by these points, resulting in significant deviation of the solution of linear equations from the normal value and poor robustness, while the random sample consensus (RANSAC) approach has insufficient fitting accuracy within a limited timeframe and the number of iterations. To address these shortcomings, we propose a spherical point cloud fitting algorithm based on projection filtering and K-Means clustering (PK-RANSAC), which strategically integrates and enhances these two methods to achieve excellent accuracy and robustness. The proposed method first uses RANSAC for rough parameter estimation, then corrects the deviation of the spherical center coordinates through two-dimensional projection, and finally obtains the spherical center point set by sampling and performing K-Means clustering. The largest cluster is weighted to obtain accurate fitting parameters. We conducted a comparative experiment using a three-dimensional ball-plate standard. The sphere center fitting deviation of PK-RANSAC was 1.91 μm, which is significantly better than RANSAC’s value of 25.41 μm. The experimental results demonstrate that PK-RANSAC has higher accuracy and stronger robustness for fitting geometric parameters.

International metrology comparison is instrumental in the establishment of a universal measurement standard and facilitating metrological traceability globally. China, being a major player in industrial manufacturing, plays a crucial role in the global commercial and manufacturing landscape, underscoring the necessity of conducting comprehensive surface roughness international comparison studies. Contact stylus profilometers, widely employed for surface roughness parameter measurement, often exhibit distortions in the measurement outcomes due to the convolution effect created during the probe-surface interface, necessitating consideration of distortions caused by probe geometric characteristics. In this study, we have conducted an in-depth investigation into the mechanism triggered by probe geometric traits inducing changes in the Ra parameter and constructed an algorithm to rectify these measurements, thereby mitigating the influence of probe geometric properties and accurately evaluating the Ra uncertainty triggered by these probe traits. Empirical evidence from this research underscores the efficacy of the devised algorithm in calculating and evaluating the Ra parameter within an international metrology surface roughness metrology comparison context, thereby facilitating effective correction of distorted data.

激光干涉仪测量纳米级分辨力时,因环境等因素的干扰测量具有局限性,电容传感器可较好地对抗这种干扰,但存在无溯源性、非线性误差的缺点.为实现纳米级分辨力的量值溯源,保障量值准确性,采用激光干涉仪对电容传感器进行校准,从而形成纳米微动台-电容传感器-激光干涉仪的完成溯源链.通过量值溯源实验可知,在10nm步进下电容传感器与激光干涉仪测量量值最大偏差为0.8 nm;电容传感器分辨力校准实验中,纳米位移台分辨力为2 nm.上述结果说明此校准方法具有一定的可行性和实用性.

基于中国计量科学研究院的表面粗糙度基准计量装置,开展了视觉定位系统、自动操作系统和多自由度位移系统的研究,从而实现依据国际比对协议规定流程的自动化测量.实验验证表明:该系统可有效实现表面粗糙度的自动化测量,满足国际比对的要求.在对国际比对规定的表面粗糙度标准器的测量实验中,该系统的自动定位测量的重复性为4.2 nm,相比于手动定位测量提高了 2.6倍,有效地减少了测量过程中引入的人为误差.

为保证计量型激光椭偏仪测量结果的准确性,研究了一种初始入射角校准方法,通过线性位移台带动CCD相机进行一维运动,其运动轴作为空间线性辅助参考量,实现了椭偏仪的入射激光光轴与自准直仪光轴的90°校准.结果表明:采用该方法校准计量型激光椭偏仪的初始入射角,光轴俯仰角偏差＜0.05°,偏摆角偏差＜0.09°;校准后,对标称值为102.10 nm的Si上Si02膜厚标准片进行测量,示值误差＜0.4 nm,提升了计量型激光椭偏仪测 量校准服务的准确性.

为了提升现有触针式表面粗糙度测量仪的计量能力,从降低仪器噪声水平的角度出发,研制了具有低噪声、无阿贝误差特性的触针式表面粗糙度探测系统.该系统采用样品扫描的方式进行接触测量,利用高精度电容传感器对触针的垂直运动进行实时测量,从而表征被测物的真实微观表面,实现了纳米尺度测量下的低噪声水平.系统使用校准触针式表面粗糙度测量仪的标准样板进行Ra测量和不确定度评估,结果表明:对Type C3标准样板测量的扩展不确定度U=2.8 nm(k=2).

台阶高度作为纳米计量领域中的一个具有代表性的参数,其评定方法层出不穷,本文对现有的台阶高度评定方法进行了介绍,并对其重复性以及一致性进行了分析.结果表明:点对点法和直方图算法受噪声等畸变影响较大,重复性较差;而对直方图算法进行改进,台阶高度由计算直方图中分别对应台阶高、低区域的峰值的横坐标之差转而计算重心的横坐标之差,重复性提高;ISO法、最小二乘多项式拟合法和光学显微解耦合准则重复性较好,计算结果更稳定.通过计算归一化偏差En值来判别6个评价方法的一致性,结果表明其测量结果等效一致.

The surface topography of micro-structures would significantly affect the products quality and industrial performance of micro-nano devices [1]. In recent years, the application of micro-structures in Micro Electro Mechanical Systems (MEMS) and integrated circuit is more and more widely. How to reflect the 3D surface topography of these micro structures accurately and measure the surface’s parameters precisely as well as quickly are becoming a hot research area of precision measurement. White-light interference microcopy technology is one of the most widely used non-contacting measurement methods at present, which has the advantages of nondestructive, fast measurement and high accuracy, has been widely applied in surface topography measurement of micro structures. In this paper, an analysis method of microstructure surface topography algorithm based on wavelet filter to analyze white interference signals is proposed, this method utilizes R/G/B three channels color information which is significantly superior to traditional black and white imaging process method. The experimental results shows that this method has good accuracy and repeatability in 3D surface measurement.

The metrological ultraviolet microscope utilizes 248nm ultraviolet light illumination and high numerical aperture objective systems,the working distance and depth of field are very small.In order to achieve a clear image,it is required the automatic focus.An auto-focus and inclination measurement algorithm is researched.Using the automatic focusing method based on image processing,the Tenengrad function is selected as the image clarity criteriont.To solve the problem that the standard model tilt and the lens may collide during the scanning measurement,a method of measuring the inclination of the template is proposed to judge the inclination angle and direction of the template,and the real-time focusing is realized.

In order to realize the rapid measurement of the nanometer scale to the micro 3D step sample height, on the basis of ordinary optical microscope, a micro/nano step height measuring device is reconstructed.The whole hardware structure is designed.The measurement and control software and data processing software are programmed.Combined with Hilbert transform and wavelet transform, a new method of algorithm which is used for the reconstruction of 3D surface topography is proposed.The step samples of different height is used to test.The measurement results indicate that this system has high measurement accuracy and high repeatability, and its measurement range in vertical direction is not less than 50 μm.

针对微纳坐标测量机的高精度性能指标无法精确校准的问题,提出了一种间接校准的方案.使用量块及标准球板校准微纳坐标测量机的尺寸测量示值误差,用标准球校准仪器的探测误差.并对中国计量科学研究院的微纳坐标测量机进行了校准实验,实验结果表明,该仪器的尺寸测量示值误小于0.2 μm,探测误差仅为0.125μm,校准结果均优于仪器的最大允许误差,验证了校准方案的合理可行性.

Temperature measurement error is the major factor to influence the precision for the nano-scale measurement in the areas of nano-structure characterization and testing. According to the materials thermophysical properties and the relationship of the air refractivity and optical measurement, metrological atomic force microscope (AFM) and the large range nano-measuring machine ( NMM ) are comprehensive studied. Firstly, high precision multipoint temperature measurement system is designed which can measure the temperature of AFM and NMM. The effect of ambient temperature variation is analyzed and evaluated in the course of scanning measurement Secondly, the related technical problems of the temperature measurement in nano-scale measurement are studied to ensure the nano-structure characterization and measurement are accurate and reliable.