Wang Hanwen, Zhu Huijie, Guo Hongwei
Appl Opt. 2023 Aug 1;62(22):5850-5860. doi: 10.1364/AO.493941.
Fringe projection profilometry is a popularly used three-dimensional measurement technique in which phase-measuring algorithms based on two-step phase shifting are usually used because of their best tradeoff between measurement resolution and speed. Most two-step phase-shifting algorithms involve neighboring or other spatial operations, thus having degraded accuracies at edges and discontinuities of the measured object surface. Pointwise two-step algorithms enable overcoming this issue. With them, however, the offsets of the dynamic ranges of the projector and camera are usually improperly overlooked or inaccurately estimated, thus inducing errors in their measurement results. For solving this problem, this paper suggests a quasi-pointwise two-step phase-shifting algorithm for fringe projection profilometry. This algorithm models the captured fringe patterns practically by taking the offsets of the dynamic ranges of the projector and camera into account, and estimates the fringe parameters from the statistics of fringe intensities. As a result, we can calculate fringe phases in a pointwise way from two fringe patterns having a phase difference of /2 radians. The simulation and experimental results demonstrate that the proposed method has a relatively low level of errors in measuring object surfaces having isolated regions and discontinuities.
条纹投影轮廓术是一种常用的三维测量技术，其中基于两步相移的相位测量算法因其在测量分辨率和速度之间的最佳权衡而被广泛使用。大多数两步相移算法涉及相邻或其他空间操作，因此在被测物体表面的边缘和不连续处精度会降低。逐点两步算法能够克服这个问题。然而，使用它们时，投影仪和相机动态范围的偏移通常会被不当忽略或估计不准确，从而在测量结果中引入误差。为了解决这个问题，本文提出了一种用于条纹投影轮廓术的准逐点两步相移算法。该算法通过考虑投影仪和相机动态范围的偏移，对捕获的条纹图案进行实际建模，并从条纹强度统计中估计条纹参数。结果，我们可以从具有π/2弧度相位差的两个条纹图案中逐点计算条纹相位。仿真和实验结果表明，该方法在测量具有孤立区域和不连续的物体表面时误差水平相对较低。
