结构光原理扩展.ppt

三维信息获取与重构技术 实体三维信息获取与重构 Rendering Shape Lighting and Reflectance Motion Shape 3D Scanning Computer Vision Dept. of Communication Eng. 结构光法背景 C1 一个图像点对应着多个空间点（一条直线无法确定一个点） C2 双摄像机可确定空间点 （两条直线相交可确定一个点） 立体视觉 Computer Vision Dept. of Communication Eng. 结构光法背景 C1 立体视觉的关键 两幅图像中对应点的确定 C2 Computer Vision Dept. of Communication Eng. 结构光法背景 C1 对应点的确定 C2 光源 Computer Vision Dept. of Communication Eng. 结构光法背景 结构光 系统构成 投影仪代替摄像机 投射特定光源解决对应问题 Computer Vision Dept. of Communication Eng. 结构光法基本原理 相似三角形 平行直线 推导 相似三角形 平行直线 Computer Vision Dept. of Communication Eng. 结构光法标定 相似三角形 平行直线 标定参数： 基线b 摄像机焦距f 投影仪投影角 Computer Vision Dept. of Communication Eng. 结构光法编码光 光源设计 Camera Laser Triangulation Depth from ray-plane triangulation Object Laser (x,y) In order to obtain a full range image, what is necessary? a system must have some methods of determining which stripe is which Slow, robust Fast, fragile Multi-stripe Multi-frame Single-frame Single-stripe ? ? Color direct coding Colored dots [Davies 96] A gray wedge [Carrihill 85] *Reflectivity assumption Eg. Fails if the surface is textured Spatial neighborhood [Boyer 87] [Proesmans 96] *Spatial coherence（空间相关） assumption Eg. Fails if surface contains discontinuities 0 1 Time-multiplexing [Sato 87] *Temporal coherence（时间相关） assumption Eg. Take several frames to compute depth Time 1010 0000 Time-multiplexing Pattern 1 Pattern 2 Pattern 3 随时间投影 该像素的编码值: 1010010 ?用于识别该点的对应关系 Designing a Code Project Code Capture Images Find Boundaries Match Boundaries Decode Compute Range Time Space Designing a Code Design a code to make tracking possible: Do not allow two spatially adjacent ghosts Do not allow two temporally adjacent ghosts t Space Time 000 001 011 101 111 110 100 010 Graph (for 3 frames): Edges: boundaries (over time) Nodes: stripes (over time) Designing a Code Designing a Code Graph (for 3 frames): 56 edges in graph ?maximal-length traversal has 64 boundaries (65 stripes) Boundary visible at one time Boundary visible