This paper proposes a novel method to achieve pose measurement in 3-D space using a microscopic camera. For an object with flange on its surface, there is a shadow region around the flange in the image if the camera is equipped with a ring light source. The flange’s shadow distribution caused by the ring light source is deduced based on imaging principle. An optimal model used to estimate object’s pose is designed based on the flange’s shadow distribution. Take the objects with circle flange, which are commonly used in precision assembly as an example, the shadow-forming model and the relation between the rotation angle and the shadow width deviation are presented. The rotation axis is determined on the basis of two particular rays on the shadow. Then the object’s orientation is computed based on the rotation axis and the rotation angle. A series of simulations and experiments are conducted to verify the high precision of the proposed pose measurement method. The root-mean-square (rms) errors of position and orientation measurement are 6.26 $\mu \text{m}$ and 0.19°, respectively.

中文翻译：

---

基于阴影分布的带法兰物体精密位姿测量

本文提出了一种使用显微相机在 3-D 空间中实现姿态测量的新方法。对于表面带有法兰的物体，如果相机配备环形光源，则图像中法兰周围会有阴影区域。根据成像原理推导出环形光源引起的法兰阴影分布。基于法兰的阴影分布设计了用于估计物体姿态的最优模型。以精密装配中常用的带圆法兰的物体为例，给出阴影的形成模型以及旋转角度与阴影宽度偏差的关系。旋转轴是根据阴影上的两条特定光线确定的。然后根据旋转轴和旋转角度计算对象的方向。进行了一系列仿真和实验以验证所提出的位姿测量方法的高精度。位置和方向测量的均方根 (rms) 误差分别为 6.26 $\mu \text{m}$ 和 0.19°。