无标记印刷品质量在线检测方法研究

Research on online quality inspection method of unmarked print

印刷品图像配准是实现印刷品自动检测的关键技术。以高分辨率印刷品图像为研究对象,将原始图像分割成多个兴趣区域,将兴趣区域的中心坐标与旋转角作为图像配准参数,通过变步长搜索算法获取被测图像与模板图像之间的最小旋转角;通过仿射变换将待检图像与模板图像进行配准并使用双向差影法计算两者的差影图像;通过二值化阈值与缺陷区域面积阈值进行缺陷识别。实验结果显示:该检测系统对合格品的检测准确率为96%,对不合格品的检测准确率为94%。

Print image registration is the key technology for achieving automatic inspection of print quality.According to print image with high resolution,original image is segmented into multiple regions of interest,center coordinates and rotation angle are treated as parameters of image registration,and the minimum rotation angle between inspected image and temple image is determined by variable step searching algorithm; an affine transformation is implemented on the inspected image and the bidirectional subtraction image between inspected image and temple image is calculated; defect is recognized by binary threshold and defect region area threshold.Experimental results indicate that the detection accuracy of the inspection system is up to 96 % for qualified products,and 94 % for unqualified products.