结构光三维测量系统标定的关键算法研究

系统参数标定是结构光三维测量系统的关键问题之一，标定板特征圆圆心检测精度与投影仪、相机镜头gamma效应引起的相位误差是系统参数标定的主要误差来源。采用Sobel算子粗定位标定板特征圆的边缘点，以正交傅里叶-马林矩(OFMM)算子对边缘点进行亚像素定位，用椭圆拟合法确定特征圆圆心的方法提高标定板特征圆检测精度。同时，推导结构光三维测量系统gamma非线性数学模型，将计算得到的系统gamma值的倒数作为投影正弦光栅的指数以降低gamma效应引起的相位误差。实验结果证明了该方法的准确性，与不采用亚像素边缘检测与gamma校正相比，X、Y方向的标定精度分别提高约3.5倍与5倍。

Crucial algorithms for structural light 3D measurement system calibration

System parameter calibration is crucial to structure light three-dimension measurement system. The calibration error is mainly due to the detection accuracy of the characteristic circular center of calibration board and the gamma distortion of the projector and camera. An accurate circular center detection method and a gamma pre-calibration method were proposed to improve calibration accuracy. The pixel edge detection with Sobel operator and sub pixel edge detection with orthogonal Fourier-Mellin moments (OFMM) operator were used to detect the circular edge accurately, moreover, the circular center was detected by ellipse fitting method. The gamma nonlinear distortion model was analyzed to obtain the system gamma value, whose reciprocal was used to modify the ideal sinusoidal fringe pattern as its exponent. The experimental results show the effectiveness of the methods. The calibration accuracy increases by a factor of 3.5 in X direction and 5 in Y direction compared with that without these methods.