中文摘要：

针对重轨生产线钢坯检测所涉及到的钢坯定位问题，提出一种基于投影不变量特征的字符定位方法。利用钢坯字符呈线性排列的特征，提出投影不变量的测量值定义；利用基于多级滤波的最大类间方差的递归分割方法，寻找满足投影不变量测量值的条件，快速寻找到钢坯字符所在的区域（即图像感兴趣区域）。最后，对感兴趣区域进行投影法的坐标定位，进而完成钢坯字符的定位问题。实验结果表明，与均值漂移的字符定位方法相比，该方法能够准确地完成字符的定位，具有良好的稳定性和准确性，提高了字符定位的正确率。

英文摘要：

Aiming at the problem of billet location of heavy rail production line ,a kind of character location method based on projective invariant features was proposed .Firstly ,the feature was presented by linear array of billet character ,the definition of the measured value of the projective invariants was put forward on the basis of it ,secondly ,the method of re‐cursive segmentation based on the variance of the largest class of multi-stage filter w as used ,by finding the satisfied con‐dition of the measured value of the projective invariants and the area of billet characters （that is the image region of inter‐est） quickly ,finally ,coordinate positioning was extracted from the image region of interest by projection ,and then com‐pleted the positioning problem of billet characters .Experimental results show that compared with the Mean Shift character positioning method ,this method can more accurately complete the location of characters ,with good stability and accuracy , improves the correct rate of the character positioning .