几种时间相位展开方法的比较

The comparison of several time phase unwrapping methods

相位场的展开是基于结构光投影光学三维面形测量方法的关键步骤,复杂相位场的展开也是该方法面临的主要问题之一,时间相位展开方法提供了解决这一难题的一种有效手段.时间相位展开方法利用从多套不同频率条纹图中调解得到的三维截断相位分布,沿时间轴方向上将每点的相位进行独立展开,可以避免二维截断相位图展开过程中引入的误差扩散问题.本文对比了负指数时间相位展开法、三频时间相位展开法、三频外差时间相位展开法以及一次外差时间相位展开法,并引入分块拟合的方法来得到更准确的相位计算结果.完成了计算机模拟和实验验证,标准平面测量时,采用分段拟和的相位误差远小于以前采用的全场拟和法.

One of the key steps in 3D optical shape measurement based on the structured light projection is the phase unwrapping. The unwrapping issue about the complicated phase map is also the difficult step of the methods. The temporal phase unwrapping provides a useful tool to obtain the continuous phase map from the complicated wrapped phase map. Along the time direction, the temporal phase un- wrapping is independently carried out from a 3D distribution demodulated from grating fringes with different pitches projected on the tested object. Therefore the problem of the error propagation in 2D phase unwrapping algorithm can be avoided. Followed by the comparison among the typical temporal phase unwrapping methods, including the negative exponential method, three pitches unwrapping method, three pitches heterodyne unwrapping method and its improved technique, a segmentation curve fitting method is used to improve the phase calculation accuracy. The computer simulations and experiments are carried out to verify that the phase error is deduced greatly through the segmentation curve fitting.