Method of controlling quality of printed images of color printing press and apparatus for controlling quality of printed images

Abstract

An object is to securely prevent incorrect reproduction of a highlight portion and an intermediate portion due to the change in condition of the printing press and incorrect reproduction of a shadow portion. The printing press includes a measuring means 12 for measuring the solid densities and the gray balance, of a printed color print image; a computing means 13 for computing respectively the differences between the solid density values and the gray balance measured by the measuring means 12 and their target values; a correction-value-computing means 14 for computing the correct values based on their differences respectively computed by the computing means 13 ; and an ink-supply-amount-adjusting means 15 for adjusting the amount of the ink of each of the basic colors to be supplied through each of plural ink fountain keys, based on the correction values computed by the correction-value-computing means 14.

Description

technical field [0001] The present invention relates to a method and an apparatus for managing the quality of printed images by individually controlling the ink supply amounts of primary color inks of a color printing machine. [0002] Background technique [0003] As a color printing machine, the following color printing machine is known, that is, equipped with a plurality of different primary colors (typically cyan (C), magenta (M), yellow (Y), black (Bk) ) a plurality of ink cartridges of printing ink of four colors) and a plurality of ink cartridge keys arranged side by side to adjust the ink supply amount from these ink cartridges, and use the ink cartridge key to adjust the ink supply amount for each ink cartridge key. The primary color inks are respectively supplied to a plurality of printing plates corresponding to the plurality of ink cartridges, and a plurality of primary color images respectively formed by the plurality of primary color inks are sequentially print...

AI Technical Summary

Problems solved by technology

[0008] In terms of solid density management, when the dot gain, etc. changes due to changes in the state of the printing press (ink viscosity, etc.), although it basically maintains The tone of the shadow area (a part with a relatively high dot area ratio) can be managed in the shadow area, but there is a disadvantage that the highlight part (a part with a relatively low dot area ratio) that is easily affected by changes in dot gain etc. part) and the middle part (the part where the dot area ratio is about 50%) tends to shift, causing poor reproduction in the highlight part and the middle part

On the other hand, in the above-mentioned gray management, even if the dot gain or the like changes, the color tone of the highlight and the middle can be basically maintained, and the color tone of the highlight and the middle can be managed, but there are the following disadvantages: , that is, the hue of the shaded portion that is easily affected by changes in dot gain etc. tends to shift, causing poor reproduction in the shaded portion

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