Self-adaptive image smoothing

Abstract

A method for image detection of a printed product (8) in a machine (4) for processing printing material by means of a computer, the resulting printed product is detected and digitized by an image detection system (2), the detected digital printed image so produced is compared by a computer with a digital reference image (15), the digital reference image is smoothed by the computer beforehand, anddispensing the wrong printed product when the digital printed image deviates from the digital reference image, before smoothing the digital reference image, the computer performs a comparison of the digital print image with the digital reference image, checks the comparison result in terms of an image area having a blurred area in the digital print image, calculating a suitable smoothing factor for these blurred image regions, and then performing a smoothing process on the digital reference image by means of the calculated suitable smoothing factor, so that the digital reference image has a similar blur in the image area as the detected digital printed image.

Description

technical field [0001] The invention relates to a method for image detection of printed matter using adaptive smoothing. [0002] The invention belongs to the technical field of automatic quality control. Background technique [0003] In today's printing industry, quality control is carried out automatically by means of so-called inline inspection systems (also called image inspection systems), especially in larger printing presses. "Inline" in this case means that the image detection system (more precisely the camera of the image detection system) is installed in the printing press. In this case, the camera is usually installed downstream of the last printing unit or, if present, another further processing station (for example a painting unit) and detects the printed products produced by the printing press. The camera can be a single camera or also a camera system with a plurality of cameras. Other image sensors may also be used. However, it is referred to as a "camera"...

AI Technical Summary

Problems solved by technology

Errors caused by image capture (e.g. due to lack of lighting, dirty lenses of cameras or other sources of influence) must not negatively affect the inspection process

[0004] A particular problem that also negatively affects inspection in this respect is irregularities in the transport of printed substrates inside the printing press

Here, the known problem is that in the case of transporting printed sheets, the lower edge of the sheet vibrates during transport through the sheet transport deflectors - that is to say, the winding up (to a certain extent the end of the sheet can be said "chatter" occurs)

However, the local image distortion factor used here does not correspond to the unsharpness caused by the movable image carrier (ie the printed sheet)

Furthermore, with the method disclosed here only linear distortions can be compensated, but not nonlinear distortions - for example in sheet offset printing due to the described roll-up of the lower edge of the sheet - cannot be compensated

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