激光CCD自准直仪圆目标中心抗噪声精确定位方法

Anti-Noise and Precise Circle Target Center Location Method of CCD Laser Autocollimator

为满足高精度计量和方位瞄准跟踪系统的发展对激光CCD自准直仪测量精度的要求,提出一种基于正交傅里叶-梅林矩的激光CCD自准直仪圆目标中心抗噪声精确定位方法。首先利用正交傅里叶-梅林矩(OFMM)的幅值旋转不变性和更低径向矩阶数在充分提取图像边缘细节信息的同时抑制图像噪声的影响,通过对图像边缘旋转后垂直方向上不同阶次的正交傅里叶-梅林矩之间关系的分析将圆目标轮廓定位至亚像素级,然后采用最小二乘拟合方法实现圆目标中心的精确定位。结果表明,该方法稳定性好,定位精度高且抗干扰能力强,改进后的激光CCD自准直仪的测量分辨力提高了10倍,测量精度由2″提高到±0.18″,可有效满足在小角度测量和瞄准等领域的高精度测量需要。

To satisfy the stringent requirements for measuring accuracies of charge coupled device （CCD） laser autocollimators in the fields, such as high accuracy metrology system, and azimuth aiming and tracing system, an anti-noise and precise circle target center location method based on orthogonal Fourier-Mellin moments （OFMMs） is proposed. The specific characteristics of the circle target edge of CCD laser autocollimators can he fully extracted, the noises in images can he efficiently diminished by using the rotation invariance and lower radial orders of the orthogonal Fourier-Mellin moments, edge location can he accomplished by setting the edge in vertical direction and analyzing the relationships among these moments of the edge, and the center position of the circle target can he accurately acquired by using the least square fitting method. Experimental results show that the proposed method is stable, accurate and immune to the noise in images, and the measuring accuracy of a modified CCD laser autocollimator is improved from 2″ to ±0.18″ with the measuring resolution increased for 10 times by using the proposed method. The proposed method can efficiently fulfill the stringent requirements of CCD laser autocollimators for high accuracies in small angle aiming and measurement.