基于差动共焦法向测量配准的自由曲面测量方法

Free-form surface measurement method based on differential confocal normal measurement registration

针对自由曲面设计坐标系和测量坐标系基准不同带来的测量问题,提出了一种基于差动共焦法向测量配准的自由曲面测量方法。方法利用差动共焦曲线过零点位置与被测点准确对应的特性,实现了对被测点的精确定焦;利用PSD在传感器焦点位置对被测点倾角进行精确测量;根据被测点倾角,利用ICP Point to Plane方法进行点云配准,提高了点云配准精度,显著提升了面形测量精度。经理论分析和初步实验证明,方法测量面形PV值的精度可以达到65nm,RMS值达到10nm,PV值与zygo干涉仪测量结果相差7nm,RMS值相差1nm,测量结果误差较小。该方法为自由曲面面形的高精度测量提供了一种新的技术途径。

Aiming at the measurement problems caused by different design coordinate system and measuring coordinate system reference system, a method of measuring free surface based on differential confocal normal measurement registration was proposed. The method utilizes the characteristic that the zero points of the differential confocal curves correspond accurately to the measured points to achieve precise focusing of the measured points. The inclination angle of the measured points is measured precisely by the PSD(Position Sensitive Detector) at the focus position. Based on the inclination angle of the measured points, the ICP(Iterative Closest Point) Point to Plane method is used for point cloud alignment to improve point cloud alignment accuracy and significantly improve surface measurement accuracy. According to the theoretical analysis and preliminary experiments, the accuracy of PV measured by this method can reach 65nm, and the RMS can reach 10nm. The difference between the PV and the zygo interferometer measurement results is 7nm, the difference between the RMS and the zygo interferometer measurement results is 1nm, which means the measurement results have small errors. The method provides a new technical approach for the surface profile measurement of freeform surface.