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An error detection and machine vision technology, applied in instruments, image data processing, calculation, etc., can solve the problems of large amount of calculation and large positioning mark overlap detection error, and achieve simple calculation method, cost saving, fast and effective positioning mark center Effect
Inactive Publication Date: 2017-06-27
TONGJI UNIV
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[0005] The invention provides an overprint error detection method based on machine vision to solve the technical problem that the existing technology has a large amount of calculation and cannot solve the technical problem of large detection errors caused by overlapping and missing positioning marks, so that the printing machine can automatically calibrate the overprint error
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Embodiment 1
[0027] Such as figure 1 As shown, this embodiment provides a method for detecting overprint errors based on machine vision, which specifically includes the following steps:
[0028] s1 collects target detection images. After a printing unit has passed through all printing steps, the camera automatically captures a fixed area on the printing unit that contains all positioning marks.
[0029] s2 establishes the xoy coordinate system according to the left and bottom edge directions of the collected target image and the specified origin position, and calculates its deflection angle relative to the xoy coordinate system through the edge of the black positioning mark. By translation and rotation, the center point of the mark is placed at the origin of the xoy coordinate system, so that the edge of the mark coincides completely with the coordinate system, and there is no deflection angle;
[0030] Specifically, taking a four-color printing machine as an example, figure 2 It is a ...
Embodiment 2
[0041] Such as image 3 As shown, this embodiment provides an overprint error detection device based on machine vision, which is suitable for automatic overprint error detection and calibration using the overprint error detection method in the above-mentioned embodiment 1, including an industrial computer 8, which is installed with Overprint error detection system, to realize the processing procedure of embodiment 1;
[0042] It also includes a black and white linear array CCD camera 3 for image acquisition, an LED light source 4 for lighting, a four-color printing machine 5, a horizontal calibration device 6 and a vertical calibration device 7;
[0043] The horizontal calibration 6 and the vertical calibration device 7 are connected to the industrial computer 8, and the calibration devices 6 and 7 are installed on the printing press 5 to calibrate printing according to the returned overprint error;
[0044] Also comprises board 9, described LED light source 4 is connected wi...
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Abstract
The present invention provides a machine vision-based overprint error detection method. According to the method, a target image is acquired through a camera, wherein the target image contains a plurality of positioning marks; the area of the positioning marks is calculated, if the difference value of the area of the positioning marks and a standard area is not larger than a specified threshold value, and template matching is used to extract the centers of the positioning marks; overprint error is detected according to the deviation quantity of the positions of the centers and standard positions; if the difference value of the area of the positioning marks and the standard area is larger than the specified threshold value, edge segmentation is adopted to extract the edges of the positioning marks, and overprint error is detected according to the deviation quantity of the positions of the edges and standard positions; and after the error detection is completed, and a printer is automatically adjusted. According to the method of the invention, the image segmentation and the template matching are utilized, so that the technical problems of large computation quantity, large error, low robustness and incapability of performing automatic adjustment according to error in the prior art can be solved. The method is suitable for being popularized in the printing industry.
Description
technical field [0001] The invention relates to intelligent manufacturing technology in the printing machine industry, in particular to a method for detecting overprint errors based on machine vision. Background technique [0002] Multi-color printing requires overlapping registration of different color plates and different graphic printing, and printing in a certain order. Therefore, the key to checking the quality of printed products is the overprint accuracy of the printing machine. [0003] The traditional overprint marks mainly include three kinds of cat's eye, single circle and cross mark. This kind of overprint mark is invented for manual detection of overprint error, so it is seriously affected by human subjective information and the efficiency of manual judgment is low and the accuracy is poor. It is difficult to apply to the current printing situation. . With the development of machine vision and digital image processing technology, it has become a trend to use d...
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