Evaluating binary defocusing quantitatively in real-time for fringe projection profilometry
Evaluating binary defocusing quantitatively in real-time for fringe projection profilometry
复制标题
实时定量评估条纹投影轮廓测量的二元散焦
DOI：
10.1117/1.oe.60.6.064110
复制
发表时间：
2021-06-01
影响因子：
1.3
通讯作者：
He, Xiaoyuan
中科院分区：
文献类型：
--
作者：
Kang, Xin;Yin, Zhuoyi;He, Xiaoyuan
抽象的。在条纹投影轮廓术（FPP）中，由于投影仪的伽马效应而产生的非正弦条纹会引起测量误差。为了解决这一问题，近年来引入了二元离焦技术，但合适的离焦量难以定量评估。提出了一种实时量化二进制散焦的创新方法。在FPP系统中，无论投影仪和摄像机如何布置，所捕获的散焦条纹图像中的条纹周期都是严格变化的，因此，与以往的方法不同，该方法使用有限窗口进行散焦评价。这不仅提高了散焦评估的准确性，而且大大提高了评估速度，从而反过来实现实时评估。此外，数值微分的窗口上使用修改的五个间隔点的算法，以有效地提高不适当的（不足或过度）离焦的敏感性。数值微分与Levenberg-Marquardt迭代法提取的基波之差作为二元离焦的评价值。差异越小，离焦越合适。通过最小化该差异，可以定量地获得最适当的散焦。数值仿真和实验结果均验证了该方法的高灵敏度和快速性。
Abstract. In fringe projection profilometry (FPP), non-sinusoidal fringes due to the gamma effect of a projector will cause measurement errors. To solve this problem, a binary defocusing technique has been introduced in recent years, yet the appropriate defocusing is hard to evaluate quantitatively. An innovative approach to quantify binary defocusing in real-time is proposed. No matter how the projector and camera are arranged in FPP system, the fringe period in a captured defocusing fringe image is strictly varying; therefore, unlike previous methods, the proposed method uses a limited window for defocusing evaluation. This not only improves the accuracy of defocusing evaluation, but also greatly improves the evaluation speed, thus in turn enabling real-time evaluation. In addition, numerical differentiation is introduced on the window using a modified five-interval-point algorithm to effectively improve the sensitivity to improper (inadequate or excessive) defocusing. The difference between the numerical differentiation and its fundamental harmonic extracted by Levenberg–Marquardt iterative is taken as an evaluation value of binary defocusing. The smaller the difference, the more appropriate is the defocusing. By minimizing this difference, the most appropriate defocusing can be obtained quantitatively. Both numerical simulations and experiments validate the high sensitivity and high speed of the proposed method.