由于接近光学衍射极限, 微米尺度线条纹在经过高倍显微镜放大成像后边缘通常都很模糊, 加上同轴光源产生的光照不均匀现象, 成像质量通常很差。为了有效测量微米尺度线条纹间距, 本文提出了一种针对光学显微线条纹图像的中心线提取算法。首先, 采用Retinex方法对原图像进行增强, 以克服由光照不均匀所造成的无法准确分割的问题。接着, 使用Ostu最佳阈值对图像进行二值分割。然后, 针对分割后条纹边缘含有大量毛刺和凹陷的现象, 使用基于快速步进算法的边缘塌陷法对中心线进行准确提取。最后, 对提取中心线进行了最小二乘拟合。实验结果表明: 本文提出的方法可以有效实现微米尺度线条纹光学显微图像中心线的准确提取。使用本方法对标准宽度线条纹间距进行实测的最大测量偏差小于2%。

Due to the proximity of the optical diffracting limitation, the edges of the stripes in micrometer scale are blurred after magnification by the optical microscope. Together with the uneven illumination caused by coaxial lighting source, the stripe image quality is very poor. To effectively measure the stripe distance between two stripes in micrometer scale, a centerline extraction algorithm was proposed. First, a single scale Retinex model was adopted to enhance the original image to overcome inaccurate segmentation caused by uneven illumination. After that, binary segmentation was conducted on the enhanced image via optimal threshold value of Ostu. Then, directing at the phenomenon that there was much rag and hollow at the boundary of stripes after segmentation, a boundary collapse method based on fast marching algorithm was utilized to extract centerline accurately. Finally, least square fitting method was conducted to fit the extracted centerlines. Experimental results show that the proposed method can effectively realize accurate extraction of stripe centerline in microscopic image with micrometer scale; the maximum measured deviation of this method is less than 2% when it is used for measuring stripe distance between two stripes with standard width.