Aiming at problems such as the image obtained by contact image sensor ( CIS) is not as clear as the scanned images, uniformly illumination and defocused imaging and other issues in the processing of series recognition on paper currency. So how to extract useful information from the low-quality images is the key step for the automatic character recognition. A solution is presented to use the homomorphic filtering to remove effect of uneven illumination and then the improved Bernsen algorithm is used for image binarization. The experimental results show the effectiveness of this algorithm, the algorithm can effectively overcome the impact of the uneven illumination and it has good binarization effect.%针对纸币冠字符识别过程中,用接触式图像传感器(CIS)获得的图像不如扫描图像清晰,同时由于不均匀光照和对焦不准等问题,所以如何将待识别的有效信息进行提取是实现冠字符自动识别的关键.提出一种解决办法,首先使用同态滤波去掉不均匀光照的影响,然后使用改进的Bernsen算法对图像进行二值化.实验结果表明了此算法的有效性,使用该算法能有效地克服不均匀光照的影响,二值化效果良好.
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