钢轨磨损视觉测量的轮廓精确快速提取

摘要

In order to ensure the high precision of dynamic visual measurement of rail abrasion,image acquisition and image processing technology were used to get clear light-stripe image and extract the sub-pixel coordinates of the light-stripe accurately.First,according to the high contrast between the light-stripe and the background brightness,a method of automatic exposure of the camera based on the brightness of the light-stripe was proposed,which could ensure a clear image of the light-stripe. Then the dynamic threshold segmentation method was presented to extract the light-stripe preliminarily according to the lightness decay feature of the light-stripe in the normal direction,this method can filter out the background of the image w hile preserving the normal attenuation of light. Finally,according to the overexposure information of the image to determine the approximate position of the center point of the light-stripe,then the Hessian matrix was calculated for the corresponding pixel position of the segmented image to obtain the sub-pixel coordinates of the light-stripe.Using MFC to write application for testing,under different illumination and background interference,this method can accurately extract the center of light-stripe,the extraction accuracy is 0.05 pixel and the computation time is reduced by 40% compared with the classical Steger algorithm.Experimental results show that the proposed method has good stability and strong anti-interference ability,can meet the requirements of the rail abrasion measurement.%为保证钢轨磨损动态视觉测量的高精度,综合图像获取和图像处理技术,实现了清晰光条图像获取和光条中心点亚像素坐标精确提取.根据光条与背景环境亮度的高对比度,提出一种依据光条亮度的相机自动曝光法,用于获取清晰的光条图像;分析图像光条法线方向的亮度衰变特征,采用动态阈值分割法初步提取光条,滤除图像背景的同时保留光条法线方向的亮度衰减信息;根据图像过度曝光信息确定光条中心点像素大致位置,再对分割的光条图像相对应像素位置点计算Hessian矩阵,获取光条中心点的亚像素坐标.采用M FC编写应用程序进行试验,在不同光照环境和背景物的干扰下,该方法可精确地提取光条中心,与经典Steger算法相比提取精度偏差为0.05 pixel,运算时间节约40%.试验结果验证了该方法稳定性好,有较强的抗干扰能力,较好地满足钢轨磨损测量的现场要求.