Three-dimensional (3D) morphology of microparts has an important influence on performance of microassembly system that mainly assembles microparts in millimetre and micron scale. Because 3D morphology of microparts cannot be accurately obtained by conventional microscopic vision system, a depth estimation method of surface of micropart in microassembly space based on microscopic vision tomographic scanning (MVTS) images is proposed in this paper. The proposed method uses the positions of pixels with the largest focus values in MVTS image to construct the isodepth contours of surface of micropart and obtains the depth values of micropart's surface at the positions of MVTS by assigning depth values to corresponding isodepth contours. The MVTS images are obtained by MVTS and pixels with the largest focus values in MVTS image are obtained by focus measurement of MVTS images of micropart in microassembly space. On these bases, 3D spatial interpolation method is applied to map depth value of space between adjacent isodepth contours and to obtain depth values of all surface of micropart. Simulation experiments are carried out to verify the proposed method by generating simulated MVTS image array from two simulation objects, and the influence parameters of the proposed method are analysed. In established experimental setup of microassembly that can realise MVTS, experimental verification for the proposed depth estimation method are carried out by using cone cavity and end jaws of microgripper. 3D morphologies of depth maps of cone cavity and end jaws of microgripper are registered with their respective CAD models using iterative nearest point registration algorithm to quantify accuracy of depth estimation. The research results show that 3D morphology of micropart can be obtained by the proposed method and has better accuracy than those by conventional shape from focus method. This method provides a new way to obtain the morphology of microparts and lays a foundation for improving the accuracy and efficiency of gripping, alignment and approaching microparts in microassembly systems.

中文翻译：

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基于显微视觉断层扫描图像的微装配空间微零件表面深度估计方法

微型部件的三维 (3D) 形态对主要组装毫米和微米级微型部件的微组装系统的性能有重要影响。针对传统显微视觉系统无法准确获取微零件3D形态的问题，本文提出了一种基于显微视觉断层扫描(MVTS)图像的微装配空间内微零件表面深度估计方法。该方法利用MVTS图像中具有最大焦点值的像素的位置来构建微件表面的等深轮廓，并通过将深度值赋给相应的等深轮廓来获得微件表面在MVTS位置处的深度值。MVTS图像是通过MVTS获得的，MVTS图像中具有最大焦点值的像素是通过微组装空间中微零件的MVTS图像的焦点测量获得的。在此基础上，应用3D空间插值法绘制相邻等深等值线之间空间的深度值，得到微零件所有表面的深度值。通过从两个模拟对象生成模拟MVTS图像阵列，通过仿真实验验证了所提出的方法，并分析了所提出方法的影响参数。在已建立的可实现 MVTS 的微组件实验装置中，利用微型夹具的锥腔和端爪对所提出的深度估计方法进行了实验验证。使用迭代最近点配准算法将微型夹具锥腔和端爪的深度图的 3D 形态与其各自的 CAD 模型配准，以量化深度估计的准确性。研究结果表明，该方法可以获得微零件的3D形貌，并且比传统的聚焦法获得的形状具有更好的精度。该方法提供了一种获取微零件形貌的新途径，为提高微装配系统中微零件抓取、对准和接近的精度和效率奠定了基础。研究结果表明，该方法可以获得微零件的3D形貌，并且比传统的聚焦法获得的形状具有更好的精度。该方法提供了一种获取微零件形貌的新途径，为提高微装配系统中微零件抓取、对准和接近的精度和效率奠定了基础。研究结果表明，该方法可以获得微零件的3D形貌，并且比传统的聚焦法获得的形状具有更好的精度。该方法提供了一种获取微零件形貌的新途径，为提高微装配系统中微零件抓取、对准和接近的精度和效率奠定了基础。