为进一步提高无衍射激光图像的定中精度,提出了一种亮环亚像素级边缘点检测方法。首先,采用局域亮度最大方法,提取亮环像素级屋脊边缘点;然后,利用线性插值算法对每一像素级边缘点进行亚像素处理进而获得亚像素边缘点;最后,用最小二乘方法,将亚像素边缘点拟合定中。分别对距离光源40 m、50 m、60 m 处,各连续拍摄的50 幅图像(图像分辨率为640×480,光靶分辨率为0.057 2 mm/pixel)进行了处理,各位置处的亚像素级边缘点x 方向定中标准差分别为0.021 4 mm、0.037 2 mm 和0.042 3 mm,y 方向定中标准差分别为0.022 8 mm、0.035 1 mm 和0.043 7 mm,明显优于像素级边缘点。实验结果表明,该方法切实可行。

In order to improve the centering precision of non-diffraction laser beam, a sub-pixel edge detection method of bright ring is proposed. The pixel roof edge points of a bright ring were detected based on maximum intensity in a local region firstly. These pixel edge points were then processed by linear interpolation to get sub-pixel edge points. Finally, the center of the laser image was calculated by using the least square method of all these sub-pixel edge points. For 50 samples captured (with a 640 pixels×480 pixels camera and 0.057 2 mm/pixel as resolution of the target) at each position at different distance of 40 m, 50 m and 60 m, the standard deviation for center fitting of the method with sub-pixel edge points was 0.021 4 mm, 0.037 2 mm and 0.042 3 mm for x, and 0.022 8 mm, 0.035 1 mm and 0.043 7 mm for y, respectively, much better than that with pixel edge points. Experiment results show that the method is feasible.