微分算子和直线拟合在十字丝中心定位中的应用

Application of Differential Operator and Linear Fitting in Crosshair Center Pinpoint

摘要: 为了满足镜头中心偏差测量中十字丝中心精确定位的要求，本文提出了一种基于微分算子和直线拟合的十字丝中心定位方法。根据十字丝成像的特殊性，首先，使用微分算子分别在X方向和Y方向求差分得到十字丝X方向和Y方向的边缘。接着，采用正交最小二乘法将刚刚得到的X方向和Y方向的边缘分别拟合为X方向和Y方向上的两条直线方程。最后，计算两条拟合直线的交点作为十字丝的中心。实验结果表明：在分辨率为1292 × 964像元为3.75 μm × 3.75 μm的CCD采集到的图像中十字丝中心的定位精度小于1个像素，在镜头中心偏差测量过程中其定位精度小于2 μm。基本满足镜头中心偏差测量对十字丝中心定位精度高、抗干扰能力强、重复性好等要求。

Abstract: In order to satisfy the requirement of crosshair center pinpoint for lens decentration measurement, a crosshair center pinpoint method based on differential operator and linear fitting is proposed. First, the edges of crosshair in both X and Y directions can be obtained by using differential operator to compute the difference in both X and Y directions. Then, two linear equations in both X and Y directions are fitted with orthogonal least square method using the edges obtained. Finally, the intersection point of the two linear equations is used as the crosshair center. Experimental results indicate that the precision of the crosshair center pinpoint is less than one pixel in the images grabbed by the CCD whose resoluntion is 1292 × 964 pixel and pixel size is 3.75 μm × 3.75 μm and the precision of pinpoint is less than 2 μm in lens decentration measurement. It can satisfy the system requirements of non-contact, online, real time, higher precision and rapid speed, as well as strong anti-jamming and stabilization.