Ekstrand Laura, Karpinsky Nikolaus, Wang Yajun, Zhang Song
3D Machine Vision Laboratory, Department of Mechanical Engineering, Iowa State University.
J Vis Exp. 2013 Dec 3(82):50421. doi: 10.3791/50421.
Digital fringe projection (DFP) techniques provide dense 3D measurements of dynamically changing surfaces. Like the human eyes and brain, DFP uses triangulation between matching points in two views of the same scene at different angles to compute depth. However, unlike a stereo-based method, DFP uses a digital video projector to replace one of the cameras(1). The projector rapidly projects a known sinusoidal pattern onto the subject, and the surface of the subject distorts these patterns in the camera's field of view. Three distorted patterns (fringe images) from the camera can be used to compute the depth using triangulation. Unlike other 3D measurement methods, DFP techniques lead to systems that tend to be faster, lower in equipment cost, more flexible, and easier to develop. DFP systems can also achieve the same measurement resolution as the camera. For this reason, DFP and other digital structured light techniques have recently been the focus of intense research (as summarized in(1-5)). Taking advantage of DFP, the graphics processing unit, and optimized algorithms, we have developed a system capable of 30 Hz 3D video data acquisition, reconstruction, and display for over 300,000 measurement points per frame(6,7). Binary defocusing DFP methods can achieve even greater speeds(8). Diverse applications can benefit from DFP techniques. Our collaborators have used our systems for facial function analysis(9), facial animation(10), cardiac mechanics studies(11), and fluid surface measurements, but many other potential applications exist. This video will teach the fundamentals of DFP techniques and illustrate the design and operation of a binary defocusing DFP system.
数字条纹投影（DFP）技术可对动态变化的表面进行密集的三维测量。与人类的眼睛和大脑一样，DFP利用同一场景在不同角度的两个视图中匹配点之间的三角测量来计算深度。然而，与基于立体视觉的方法不同，DFP使用数字视频投影仪取代其中一个相机(1)。投影仪快速将已知的正弦图案投射到物体上，物体表面会在相机视野中使这些图案发生畸变。相机采集到的三个畸变图案（条纹图像）可用于通过三角测量计算深度。与其他三维测量方法不同，DFP技术使得系统往往速度更快、设备成本更低、更灵活且更易于开发。DFP系统还能实现与相机相同的测量分辨率。因此，DFP和其他数字结构光技术最近成为了深入研究的焦点（如(1 - 5)中所总结）。利用DFP、图形处理单元和优化算法，我们开发了一个系统，能够以30Hz的频率采集、重建和显示三维视频数据，每帧超过300,000个测量点(6,7)。二元散焦DFP方法可以实现更高的速度(8)。多种应用都能从DFP技术中受益。我们的合作者已将我们的系统用于面部功能分析(9)、面部动画(10)、心脏力学研究(11)以及流体表面测量，但还有许多其他潜在应用。本视频将介绍DFP技术的基本原理，并阐述二元散焦DFP系统的设计与操作。
