基于复合光栅投影的快速傅里叶变换轮廓术

在实际傅里叶变换轮廓术测量中，获取条纹图的零频分量对傅里叶变换轮廓术的测量精度和测量范围有很大影响，甚至妨碍三维面形的正确重建。π相移技术常被用来消除零频分量对傅里叶变换轮廓术测量的影响，但它需要采集两帧具有π相位差的条纹图。这影响了傅里叶变换轮廓术测量方法的实时性。提出采用复合光栅投影来实现从一帧条纹图中消除零频对傅里叶变换轮廓术测量的影响，该复合光栅是由两个不同频率的载频分别调制与其方向垂直的两帧具有π相位差的条纹并叠加形成的。实验表明，同传统的π相移方法相比，提出的新方法没有明显降低π相移傅里叶变换轮廓术的的测量精度，因此能真正实现实时高速测量。

Improved Fast Fourier Transform Profilometry Based on Composite Grating

In Fourier transform profilometry (FTP), zero frequency of the captured patterns influences the measuring range and measuring precision, and even makes the reconstruction of three-dimensional surface incorrect. π phase shifting technique is usually used to eliminate the zero component. But this method needs capturing two fringe patterns with π phase difference, which influences the real-time application of the method. Now a novel method is proposed, in which a composite pattern is projected. The composite pattern is formed by modulating two separate fringe patterns with π phase difference along the orthogonal direction of the two distinct carrier frequencies. The method can eliminate zero frequency by using only one fringe pattern. The experiments show that there is no distinct decrease in the precision of the novel method compared with the traditional π phase shifting technique. So, the novel method can allow for real-time and high-speed implementation.