加权整体最小二乘法在光学自准直法测量挠曲角中的应用

建立了基于光学自准直法的测量系统,利用该系统提取转台的十字丝坐标,完成了对三维物体的挠曲角测量.首先,采用Sobel提取算子对CCD拍摄到的十字丝图像进行边缘检测.然后,采用了自适应的阈值分割进行直线提取；由于转台上有其它划痕存在,采用局部最小二乘进行十字丝的提取.最后,采用加权整体最小二乘法进行十字丝两条线的直线拟合,联立两方程,得出交点坐标值.结果表明,此方法获取的两直线斜率之积的精度在±1％以内,非常接近十字丝斜率之积的真值(理论真值为-1).使用徕卡经纬仪(精度为0.5″)的角度值作为真值进行精度标定,测得a的精度为3.59″,β的为3.76″,完全满足系统挠曲角测量的精度要求.

Application of weighted total least squares in measurement of deflection angle with optical self-collimation method

A self-collimating optical measurement system was set up to measure the deflection angles of three-dimensional objects,in which the values of the deflection angles were obtained by extracting the coordinate of a turntable cross wire.First,Sobel operator was used to detect the image edge of the cross wire taken by a CCD camera,then lines of the cross wire were extracted through self-adaptive threshold division.Because of other turntable scratches,the partial least square method was used to extract the cross wire,and the weighted total least squares was adapted to fit the cross-wire lines.Thus two equations were set up,and the intersection coordinate was obtained through solving the two equations.Experimental results show that the precision of the two line-slope product is within ±1%,very close to the true value(theoretical true value is-1).By taking the angle from Leica theodolite(the accuracy is 0.5″) as the true value to calibrate the precision,the measured precision angles for α and β are 3.59″ and 3.76″,respectively,which satisfies the requirements of deflection angle measurement.