作者丨Tom Hardy
编辑丨3D视觉工坊
结构光投影三维成像目前是机器人3D 视觉感知的主要方式,结构光成像系统是由若干个投影仪和 相机组成, 常用的结构形式有: 单投影仪-单相机、单投影仪-双相机 、单投影仪-多相机、单相机-双投影 仪和单相机-多投影仪等典型结构形式。
结构光投影三维成像的基本工作原理是：投影仪向目标物体投射特定的结构光照明图案,由相机摄取被目标调制后的图像,再通过图像处理和视觉模型求出目标物体的三维信息. 常用的投影仪主要有下列几种类型:液晶投影(LCD)、数字光调制投影(DLP)[如数字微镜器件 (DMD)]、激光 LED图案直接投影. 根据结构光投影次数划分,结构光投影三维成像可以分成单次投影3D和多次投影3D方法.
按照扫描方式又可分为：线扫描结构光、面阵结构光
参考链接：https://zhuanlan.zhihu.com/p/29971801
结构光三维表面成像：综述（一）：https://www.jianshu.com/p/e26ab208962c
结构光三维表面成像：综述（二）：
https://www.jianshu.com/p/b0e030f3a522
结构光三维表面成像：综述（三）：
https://www.jianshu.com/p/c8d0afd817cc
综述
1.Structured-light 3D surface imaging: a tutorial：http://www.rtbasics.com/Downloads/IEEE_structured_light.pdf
2.机器人视觉三维成像技术综述：http://www.opticsjournal.net/Articles/Abstract?aid=OJ9aea62c85c7ac99d
3.Real-time structured light profilometry a review:
https://github.com/Tom-Hardy-3D-Vision-Workshop/awesome-3D-vision/blob/master
4.A state of the art in structured light patterns for surface profilometry:
https://github.com/Tom-Hardy-3D-Vision-Workshop/awesome-3D-vision/blob/master
5.Phase shifting algorithms for fringe projection profilometry: a review:
https://github.com/Tom-Hardy-3D-Vision-Workshop/awesome-3D-vision/blob/master
6.Overview of the 3D profilometry of phase shifting fringe projection:
https://github.com/Tom-Hardy-3D-Vision-Workshop/awesome-3D-vision/blob/master
7.Temporal phase unwrapping algorithms for fringe projection profilometry:a comparative review:
https://github.com/Tom-Hardy-3D-Vision-Workshop/awesome-3D-vision/blob/master
Lectures&Video
1.Build Your Own 3D Scanner: Optical Triangulation for Beginners:
http://mesh.brown.edu/byo3d/
2.github.com/nikolaseu/th:
https://github.com/nikolaseu/thesis
3.CS6320 3D Computer Vision, Spring 2015
标定
1.高效线结构光视觉测量系统标定方法：
http://www.opticsjournal.net/Articles/Abstract?aid=OJ590c414efec735a
2.一种新的线结构光标定方法：
http://www.opticsjournal.net/Articles/Abstract?aid=OJ6ca613096af02c49
3.一种结构光三维成像系统的简易标定方法：
http://www.opticsjournal.net/Articles/Abstract?aid=OJ8214561beb0d211d
4.基于单应性矩阵的线结构光系统简易标定方法：
http://www.opticsjournal.net/Articles/Abstract?aid=OJ200109000160x5A8D0
5.线结构光标定方法综述：
http://www.opticsjournal.net/Articles/Abstract?aid=OJ180307000127TqWtZv
6.三线结构光视觉传感器现场标定方法：
http://www.opticsjournal.net/Articles/Abstract?aid=OJ180908000212OkRnTq
7.单摄像机单投影仪结构光三维测量系统标定方法：
http://www.opticsjournal.net/Articles/Abstract?aid=OJ180808000091UrXu1w
8.超大尺度线结构光传感器内外参数同时标定：
http://www.opticsjournal.net/Articles/Abstract?aid=OJ180319000030HdJgMj
9.单摄像机单投影仪结构光三维测量系统标定方法：
http://www.opticsjournal.net/Articles/Abstract?aid=OJ180808000039aHdKgM
10.三维空间中线结构光与相机快速标定方法：
http://www.opticsjournal.net/Articles/Abstract?aid=OJ170329000177sZv2y5
11.线结构光传感系统的快速标定方法：
http://www.opticsjournal.net/Articles/Abstract?aid=OJ091028000118B8DaGd
单次投影成像
单次投影结构光主要采用空间复用编码和频率复用编码形式实现 ,常用的编码形式有:彩色编码 、灰度索引、 几何形状编码和随机斑点. 目前在机器人手眼系统应用中,对于三维测量精度要求不高的场合,如码垛、拆垛、三维抓取等,比较受欢迎的是投射伪随机斑点获得目标三维信息 。
1.One-shot pattern projection for dense and accurate 3D acquisition in structured light
2.A single-shot structured light means by encoding both color and geometrical features
3.Dynamic 3D surface profilometry using a novel colour pattern encoded with a multiple triangular mode
4.Review of single-shot 3D shape measurement by phase calculation-based fringe projection techniques
5.Robust pattern decoding in shape-coded structured light
多次投影成像
多次投影3D方法主要采用时间复用编码方式实现,常用的图案编码形式有:二进制编码、多频相移编码和混合编码法(如格雷码＋相移条纹)等.
但是格雷码方法仅能在投射空间内进行离散的划分,空间分辨率受到成像器件的限制. 为了提高空间分辨率,需要增加投影条纹幅数,投射条纹宽度更小的格雷码条纹图,但条纹宽度过小会导致格雷码条纹的边缘效应,从而引 起解码误差.
正弦光栅条纹投影克服了格雷码空间离散划分的缺点,成为使用率最高的结构光类型之一. 众所周知,对于复杂外形,如有空洞、阶梯、遮挡等,采用正弦单频相移法条纹投影时,存在相位解包裹难题.另外为了能够从系列条纹图中求出相位绝对值,需要在条纹中插入特征点,比如一个点、一条线作为参考相位点,但是这些点或线特征标志有可能投影在物体的遮挡或阴影区域,或受到环境光等干扰等,发生丢失,影响测量结果的准确性. 因此,对于复杂轮廓的物体,常采用多频相移技术.
1.三维重建的格雷码-相移光编码技术研究
2.Pattern codification strategies in structured light systems
3.Binary coded linear fringes for three-dimensional shape profiling
4.3D shape measurement based on complementary Gray-code light
5.Phase shifting algorithms for fringe projection profilometry: a review
6.Overview of the 3D profilometry of phase shifting fringe projection
7.Temporal phase unwrapping algorithms for fringe projection profilometry:a comparative review
8.A multi-frequency inverse-phase error compensation method for projectornon linear in3D shape measurement
偏折法成像
对于粗糙表面,结构光可以直接投射到物体表面进行视觉成像测量;但对于大反射率光滑表面和镜面物体3D 测量,结构光投影不能直接投射到被测表面,3D测量还需要借助镜面偏折技术 .
1.Principles of shape from specular reflection
2.Deflectometry: 3D-metrology from nanometer to meter
3.Three-dimensional shape measurement of a highly reflected specular surface with structured light method
4.Three-dimensional shape measurements of specular objects using phase-measuring deflectometry
由于单次投影曝光和测量时间短,抗振动性能好,适合运动物体的3D测量,如机器人实时运动引导,手眼机器人对生产线上连续运动产品进行抓取等操作. 但深度垂直方向上的空间分辨率受到目标视场、镜头倍率和相机像素等因素的影响,大视场情况下不容易提升。
多次投影方法(如多频条纹方法)具有较高空间分辨率,能有效地解决表面斜率阶跃变化和空洞等难题. 不足之处在于:
1.对于连续相移投影方法,3D重构的精度容易受到投影仪、相机的非线性和环境变化的影响;
2.抗振动性能差,不合适测量连续运动的物体;
3.在Eye-in-Hand视觉导引系统中,机械臂不易在连续运动时进行3D成像和引导;
4.实时性差,不过随着投影仪投射频率和CCD/CMOS图像传感器采集速度的提高,多次投影方法实时3D 成像的性能也在逐步改进；
偏折法对于复杂面型的测量,通常需要借助多次投影方法,因此具有多次投影方法相同的缺点.另外偏折法对曲率变化大的表面测量有一定的难度,因为条纹偏折后的反射角的变化率是被测表面曲率变化率的２倍,因此对被测物体表面的曲率变化比较敏感,很容易产生遮挡难题.
Other Papers
1.基于面结构光的三维重建阴影补偿算法
2.Enhanced phase measurement profilometry for industrial 3D inspection automation：
3.Profilometry of three-dimensional discontinuous solids by combining two-steps temporal phase unwrapping, co-phased profilometry and phase-shifting interferometry：
4.360-Degree Profilometry of Discontinuous Solids Co-Phasing ２-Projectors and１-Camera：
https://github.com/Tom-Hardy-3D-Vision-Workshop/awesome-3D-vision/blob/master
5.Coherent digital demodulation of single-camera N-projections for 3D-object shape measurement Co-phased profilometr：
https://github.com/Tom-Hardy-3D-Vision-Workshop/awesome-3D-vision/blob/master
6.High-speed 3D image acquisition using coded structured light projection：
7.Accurate 3D measurement using a Structured Light System：
8.Structured light stereoscopic imaging with dynamic pseudo-random patterns：
9.Robust one-shot 3D scanning using loopy belief propagation：
10.Robust Segmentation and Decoding of a Grid Pattern for Structured Light：
11.Rapid shape acquisition using color structured light and multi-pass dynamic programming：
https://ieeexplore.ieee.org/document/1024035/
12.Improved stripe matching for colour encoded structured light：
https://github.com/Tom-Hardy-3D-Vision-Workshop/awesome-3D-vision/blob/master
13.Absolute phase mapping for one-shot dense pattern projection：
14.3D digital stereophotogrammetry: a practical guide to facial image acquisition：
https://github.com/Tom-Hardy-3D-Vision-Workshop/awesome-3D-vision/blob/master
15.Method and apparatus for 3D imaging using light pattern having multiple sub-patterns：
https://github.com/Tom-Hardy-3D-Vision-Workshop/awesome-3D-vision/blob/master
16.High speed laser three-dimensional imager：
https://github.com/Tom-Hardy-3D-Vision-Workshop/awesome-3D-vision/blob/master
17.Three-dimensional dental imaging method and apparatus having a reflective member：
https://github.com/Tom-Hardy-3D-Vision-Workshop/awesome-3D-vision/blob/master
18.3D surface profile imaging method and apparatus using single spectral light condition
https://github.com/Tom-Hardy-3D-Vision-Workshop/awesome-3D-vision/blob/master
19.Three-dimensional surface profile imaging method and apparatus using single spectral light condition：
https://github.com/Tom-Hardy-3D-Vision-Workshop/awesome-3D-vision/blob/master
20.High speed three dimensional imaging method：
https://github.com/Tom-Hardy-3D-Vision-Workshop/awesome-3D-vision/blob/master
21.A hand-held photometric stereo camera for 3-D modeling：
https://github.com/Tom-Hardy-3D-Vision-Workshop/awesome-3D-vision/blob/master
22.High-resolution, real-time 3D absolute coordinate measurement based on a phase-shifting method：
https://github.com/Tom-Hardy-3D-Vision-Workshop/awesome-3D-vision/blob/master
23.A fast three-step phase shifting algorithm：
https://github.com/Tom-Hardy-3D-Vision-Workshop/awesome-3D-vision/blob/master
Code
1.github.com/jakobwilm/sl：
https://github.com/jakobwilm/slstudio
2.github.com/phreax/struc：
https://github.com/phreax/structured_light
3.github.com/nikolaseu/ne：
https://github.com/nikolaseu/neuvision
4.github.com/pranavkantga：
https://github.com/pranavkantgaur/3dscan
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