Process and apparatus for evaluating printing quality and for regulating the ink feed controls in an offset printing machine
US4649502A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Oct 29, 1984 |
| Grant date | Mar 10, 1987 |
| Priority date | — |
| Expiry date | Oct 29, 2004 |
Classification
- Technology area (CPC B)Performing Operations; Transporting
- CPC primaryB41F33/0045
- WIPO fieldTextile and paper machines
- WIPO sectorMechanical engineering
Abstract
The printed sheets are scanned, by image elements, immediately behind the last printing mechanism, with one or several measuring heads. Suitable dimensions of an image element range from approximately 1.times.1 mm.sup.2 to 10.times.10 mm.sup.2. In each image element the reflectance is measured in four spectral ranges (infrared for black, red for cyan, green for magenta and blue for yellow). The measured reflectance values are converted by means of Neugebauer equations into surface coverages in a demasking step and inputted to a computer for evaluation. With the same measuring device, both the reference values associated with OK sheets, and the actual values associated with continuous printing, are measured. The computer compares the measured data, weights them with respect to such factors as surface coverage, foreign color component and the environment of a respective image element, and produces a regulating signal to control the ink feed elements. The color coordinates (X,Y,Z) may be determined from the surface coverage values of the four colors in a parallel computer program. Image elements which are important for the visual appearance of an image are given a high weight. A quali…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.