套准偏差自动检测方法

目前，国内多色印刷机多采用手动方式调整套准精度，自动化程度较低，为解决该问题，提出一种套准偏差自动检测方法。基于视觉成像原理拍摄套准标记图像，采用图像分析理论建立套准偏差计算方法。通过彩色图像矢量信号滤波法预处理标记图像并提取图像目标，给出青(C)、品红(M)、黄(Y)、黑(B)四种原色及其复合色像素的分色归类模型，在此基础上检测四种原色套准标记的边缘像素，进一步结合最小二乘和Hough变换法拟合套准标记的多条边缘直线，最后在图像中计算四种原色特征直线之间的偏移距离，通过视觉标定给出物空间的套准偏差。试验结果表明该方法自动检测套准偏差的精度高于20 μm，符合国家印刷行业标准规定的套准精度要求，适用于以C、M、Y、K合成原理为基础的双色、四色胶印系统。

Automatic Detected Method of Register for Color Printing

Now, the registration precision usually adjusted by handwork that is an undeveloped method for multi-color printing machines in china. To solve this problem, an automatic detection method of color registtration is proposed. Registration marker image is photographed on the basis of visual imaging principle, and the calculation method of registration deviation is established by adopting the image analysis theory. Marker images are preprocessed by using the vector signal filtering method of color image, and image objects are extracted, so a color recognition model for cyan, magenta, yellow and black primary colors and their complex color pixels is derived. The next step is that edge pixels of color marker are extracted, and their structural lines are approximated by least square fitting and Hough transform method. At last, relative distances among registration markers on image are calculated and translated into relative distances in object space via vision calibration methods. Experiments indicate that precision of 20 micron is obtained when this automatic detection method is applied. And this accords with general printing technology standard of china. This method can be applied to two or four color offset printing system based on the CMYK synthesis principle.