A three-step system calibration procedure with error compensation for 3D shape measurement

System calibration, which usually involves complicated and time-consuming procedures, is crucial for any three-dimensional （3D） shape measurement system based on vision. A novel improved method is proposed for accurate calibration of such a measurement system. The system accuracy is improved with considering the nonlinear measurement error created by the difference between the system model and real measurement environment. We use Levenberg-Marquardt optimization algorithm to compensate the error and get a good result. The improved method has a 50% improvement of re-projection accuracy compared with our previous method. The measurement accuracy is maintained well within 1.5% of the overall measurement depth range.     

Registration and integration algorithm in structured light three-dimensional scanning based on scale-invariant feature matching of multi-source images

Based on the homography between a multi-source image and three-dimensional (3D) measurement points, this letter proposes a novel 3D registration and integration method based on scale-invariant feature matching. The matching relationships of two-dimensional (2D) texture gray images and two-and-a-half- dimensional (2.5D) range images are constructed using the scale-invariant feature transform algorithms. Then, at least three non-collinear 3D measurement points corresponding to image feature points are used to achieve a registration relationship accurately. According to the index of overlapping images and the local 3D border search method, multi-view registration data are rapidly and accurately integrated. Experimental results on real models demonstrate that the algorithm is robust and effective.     

三维重建的格雷码-相移光编码技术研究

提出一种基于格雷码-相移的组合光编码技术, 以格雷码技术自身的误差不累加性优点保证了光编解码的稳健性, 针对格雷码对视场解析的有限性缺陷, 提出将格雷码部分作为编码的整数部分, 综合使用相移编码作为小数部分, 实现了视场空间的无级细分, 提高了编码的分辨率, 对编码技术中常见的两种错误, 使用提出的编码校正算法有效的减少了编码错误及重建误差的产生。试验结果表明这种光信号编码方法在三维测量中的有很高的稳健性。     

面向结构光三维测量的高稳定映射拼接方法

基于自由视角测量的三维拼接大大提高了测量的便捷性,为了提高视角间三维映射的稳健性,提出了一种改进的高稳定映射拼接方法。根据图像间匹配的特征点实现视角重合,利用结构光相位信息完成特征点三维映射和空间定位。针对特征点相位缺失无法重建的普遍问题,提出利用邻域点插值恢复特征点方法,虚拟重建视角间有效映射点,通过四元数法实现视角间点云的刚性变换和拼接。实验表明,相较传统的方法,该方法平均能将有效特征点数量提升20%,有效提高了映射拼接的稳定性。     

面向彩色物体的双目三维测量编码新方法

为了实现彩色物体三维(3D)形貌的精确测量,提出了一种新的面向双目立体匹配的彩色编码方法。根据三原色(RGB)颜色空间模型和光谱原理对不同颜色赋予相应的视觉编码值,设定相邻彩色条纹波长变化明显、颜色差别大、码值唯一的原则并进行编码设计;利用改进的色彩标定方法消除背景色彩的影响;实验验证了提出的彩色编码方法。结果表明,该编码新方法消除了物体彩色纹理背景的影响,满足了彩色物体三维形貌精确测量的要求,可以快速、有效地实现彩色物体的三维形貌测量。     

Linear sinusoidal phase-shifting method resistant to non-sinusoidal phase error

Non-sinusoidal phase error is common in structured light three-dimensional（3D）shape measurement system,thus we perform theoretical and experimental analyses of such error.The number of non-sinusoidal waveform errors in a 2πphase period is the same as the number of steps of the phase-shifting algorithm;no errors occur within the one-phase period.Based on our findings,a new structured light method,the linear sinusoidal phase-shifting method（LSPS）,that is resistant to non-sinusoidal phase error is proposed.Experiments show that the non-sinusoidal waveform error is reduced to an almost negligible level（0.001 rad） using the proposed LSPS.     

基于单应性矩阵的变焦双目视觉标定方法

针对现有变焦镜头标定方法难度大、动态精度低等问题,提出一种基于单应性矩阵的动态变焦双目内外参数估计方法和平面快速重建方法。利用双目图像匹配点及变焦前后的匹配点进行两类单应性矩阵估计;基于变焦数学模型和单应性矩阵,求解变焦后双目内外参数,实现畸变后双目参数动态估计与优化;通过双目图像单应性进行平面快速匹配和重建。实验结果表明,计算的内外参数与标定结果吻合较好;变焦后,推导的单应性矩阵归一化误差小于0.01,图像重投影误差小于1pixel;重建精度小于0.1mm。