子孔径拼接干涉仪中子孔径定位精度难以在大行程范围内得到保证，为此本文提出了基于提取标记点中心定位子孔径的拼接方法。以标记点的中心坐标为标记点坐标，根据标记点在两子孔径局部坐标系下的坐标计算两子孔径之间的坐标变换，将所有子孔径数据坐标变换到统一坐标系下，利用机械误差补偿算法拼接出全口径面形。在搭建的拼接检测系统上实现了外径468 mm的平面镜抛光过程和最终的全口径面形测量，加工过程中的测量结果为面形误差修正提供了准确的数据，保证了最终全口径面形误差RMS快速收敛到35 nm。实验证明，基于提取标记点中心的子孔径拼接检测能放宽对机械定位精度的要求，有效检测大口径光学元件面形。

The stitching interferometer systems with larger relative movement will show a significantly lower positioning accuracy of subapertures. As a consequence a stitching method based on detection of artificial circular mark center to find the necessary translation between two neighborly subapertures is implemented. Firstly, we take coordinates of mark centers as the marks′ coordinates by which the translation is computed. Then all the subaperture data are unified into the same reference by homogeneous coordinate transformation and the full aperture phase are stitched by using mechanical system error compensation algorithm. A subaperture stitching process for a 468 mm flat mirror was carried out including surface accuracy tests during the polishing. In this process, subaperture stitching test offered the surface data precisely for polishing, which ensured the surface error converged quickly to a final RMS of 35 nm. The experimental results show that the method relaxes the precision requirement for subaperture location and can get the full aperture phase for large optical element correctly.