基于DMD时空调制特性的高反光表面动态三维面形测量方法研究

In three-dimensional scanning measurement based on structural light technology, high-reflective surface produces specular reflected light, which easily leads to partial oversaturation for the image brightness of digital camera, resulting in measurement blind-spot. Meanwhile, limited by the acquisition speed of digital camera, its dynamic three-dimensional shape measurement is also difficult to realize. For the problems of visual imaging and dynamic three-dimensional surface shape measurement of high-reflective surfaces, the elimination method of local specular high-light based on adaptive high dynamic range imaging is studied, and the mapping relationship between the optical scattering characteristics of high-reflective surface and the spatial modulation characteristics of digital micromirror device (DMD) will be explored to effectively extract the surface features of high-light region. By revealing the coupling mechanism between the temporal modulation characteristics of DMD and the pixels grayscale of image detector, the dynamic three-dimensional surface shape measurement method based on pixel temporal multiplexing and multi-frequency heterodyne phase shift is proposed. On this basis, a novel three-dimensional scanning measurement system based on computational imaging is constructed to realize the dynamic three-dimensional surface shape measurement of the high-reflective surface. This research can overcome the limitation of imaging dynamic range and temporal resolution of common industrial digital cameras, and presents a new idea of dynamic 3d surface shape measurement of high-reflective surface based on the spatio-temporal modulation characteristics of DMD, which will lay a foundation for industrial applications.

在结构光三维扫描测量中，高反光表面产生的局部镜面反射光容易使数字相机采集的图像亮度出现局部过饱和，造成测量盲点；受数字相机图像采集速度的限制，其动态三维面形测量难以实现。针对高反光表面的视觉成像与动态三维面形测量问题，本项目研究基于自适应高动态范围成像的局部镜面高光消除方法，探索高反光表面的光学散射特性与数字微镜器件（Digital Micromirror Device，DMD）空间调制特性之间的映射规律，以有效提取局部高光区域的面形特征；揭示DMD时间调制特性与图像探测器像素灰度值之间的耦合机理，提出基于像素时域多路复用与多频外差相移的动态三维面形测量方法；在此基础上，构建基于计算成像的三维扫描测量系统，实现对高反光表面的动态三维面形测量。本研究突破了普通工业数字相机的成像动态范围和时间分辨率的限制，提出了基于DMD时空调制特性的高反光表面动态三维面形测量的新思路，为工业应用奠定基础。

在现代高端装备制造领域，高反光表面的视觉成像与三维测量已成为几何量精密测量领域亟待解决的关键共性难题之一。本项目深入研究基于数字微镜器件时空调制特性的高反光表面三维面形测量方法，达到了预期研究目标。一方面，研究基于高动态范围成像的局部镜面高光消除与三维面形测量方法，通过光强编码控制算法可自适应衰减高反光表面的局部高光区域的光强，扩大测量系统的成像动态范围，从根源上消除高反光表面存在的局部镜面高光对视觉成像与测量的影响。另一方面，深入研究基于数字条纹投影与多频外差相移的高反光表面三维测量方法，该方法既无需附加或改进任何硬件设备，也无需大量采集和投射不同曝光时间和曝光量的条纹图案，能有效并自适应地求解最佳投影强度，并研制面向高反光零部件的光学三维精密测量样机与系统，先后实现了对不同类型的高反光表面的三维测量。此外，开展新型的基于结构光场调制的高反光表面三维重建方法研究，借助光场成像具有多视角成像的特性，提出基于相位相似性的光场三维重建方法，并研究基于多频外差与自适应点云修复的结构光场三维重建方法，初步实现高反光表面视觉成像与三维重建。本项目始终聚焦于高反光表面的视觉成像与三维测量方面的研究，突破了传统数字成像的局限，为制造领域提供了新的检测手段，并有望在高端装备制造领域得到应用。