DE4242683A1 - Controlling ink application in printer unit - Google Patents

Abstract

Colour measurement values acquired by a scanner are compared with desired values and the results used to influence control units for the ink application. The colour values are summed, integrated and displayed as a vector in colour space. The scanner detects the primary colours red, green and blue, which are converted into cyan, magenta, yellow and key.The demand values from different printing plates are combined to form a colour vector in any selected colour space. This vector is then compared with the actual colour vector.

Description

The invention relates to a method for controlling a Color application in a printing unit, in which printing plates be entered, as well as a device for this.

Colored printed matter is used in everyday life indispensable. These include, for example, magazines, Catalogs, books, brochures or the like. It is the job the printing technology to implement metameric templates so that the Color rendering in print compared to the original only shows slight deviations. That is, after "Color valence metric" aspects are worked on.

In order to be able to measure a color, a procedure is required that mimics the function of the eye (the color valence metric). This presents considerable difficulties, since the color is not a physical quantity, but rather the evaluation of a template and its evaluation in the direction of the color in the eye and in the brain take place. The human eye can recognize up to 200 shades (tone levels), which means three basic colors: yellow, magenta, cyan = 200 ³ = 8 million color combinations. Only the difficulty of a measurement method for the color can be seen from this.

This is a common measuring device in the printing industry Densitometer. With the densitometer there is a color density determined, but a densitometer is not usable Measurement result of the color appearance of a template delivers.

However, an exact analysis of a template color is only possible using the spectrophotometer method. This too is at the speed with which, for example, today Rotary presses work, cannot be used.

Furthermore, a method is known from EP-A 228 347, in one for optimal adjustment of the color impression A large number of color measuring fields are designed as reference fields become. The spectral color analysis of a variety of Color measurement fields, as well as the calculation of a variety of Color coordinates for each printing plate require one relatively high effort. This effort is still going on thereby increased that in the known method for each of the numerous reference fields weighted distance vectors as a measure of quality for printing Total color difference, which is the sum of the amounts of individual color differences is determined to minimize.

EP-B 324 718 improves this process. There are those printed on by the printing press Printing sheets Color measuring strips with several color measuring fields also printed with the help of a measuring head for detection the spectral intensity distributions of the color measuring fields to be optically scanned to from a spectral Color analysis of the measuring light, the spectral remissions and  the color locus of a reference field of a scanned one To determine the color measuring field in a color coordinate system and by comparing coordinates from the color difference of the scanned color measurement field from a predetermined target Color locus variables for adjusting the color guide elements of the printing press so that unwanted Color deviations in those with the new color guide Then set the printed sheet become minimal. The are used to determine the color distance spectral reflectance values of a reference field in the form of a Grid as the main variable for determining an actual Color locus detected. The spectral remissions of as Color fields serving as secondary fields are called secondary quantities detected and from them the sensitivity of the Color locus shift calculated.

This process is also extremely complex and the speed at which today's printing presses work, not applicable.

EP-A 0 228 347 also works with color measuring fields that can be evaluated by spectral measurements. The selected color measurement fields only offer one Additional information, but have little meaning about the actual color impression.

The present invention is based on the object Method and device of the above Kind of develop by means of which in the simplest possible way Optimum of a paint job determined and the corresponding ink rollers can be controlled.

To solve this problem, that color values of Color order determined line by line by a scanner with Target values compared and then controls for the Color application can be addressed.  

That means not about determining values a color measurement field, but the determination of Color values of an entire line. An appropriate scanner For example, 5,000 per line and per primary color Color values determine what is the width of the artwork of 1,400 mm means a color value range of 0.28 mm. Such a method works extremely quickly and is hence the high-speed rotary printing press customized. A maximum of is obtained via the process Statements regarding the actual color values, which then be compared with target values. The determined color values on sum and integrated and as a corresponding vector is shown in the color space.

Using this method, the static Errors, the wear of the color control elements, the measurement and the color coverage, and also the dynamic Error, d. that is, the speed, the feeding of the Colors, dampening solution supply, temperature influences and paper properties corrected and balanced.

Usually the scanner only takes the color values as Remission color values RGB (red-green-blue) so that they are on can be displayed on a corresponding screen.

Before actuating the Controls are done, the remission colors must be in the Converted primary colors cyan, magenta, yellow and key become. This is done in a corresponding computer.

In one embodiment of the invention it is possible that the target values for the paint application are known and specified are. However, this will rarely happen. In As a rule, it is desirable that the target values be direct be determined from the pressure plates. It means that the printing plates previously a printing plate scanner  run through, which determines the aforementioned target values and via which the control elements are regulated. The Correction of the controls based on the comparison of the Actual values with the target values then take place from the Result of the scanner following the printing unit.  

Further advantages, features and details of the invention result from the following description of a preferred embodiment and based on the Drawing; this shows one in her only figure Block diagram representation of the invention Process for controlling a color application in a Printing press.

The printing plates 1 , not shown in more detail, contain the information for an ink application for the production, for example, of a magazine page. Here are z. B. four printing plates are provided, on each of which a base color is applied. The printing plate 1 C is intended for the basic color cyan, the printing plate 1 M the basic color magenta, the printing plate 1 Y the basic color yellow and the printing plate 1 K the basic color Key, usually black.

Each of these printing plates 1 is received by a printing plate scanner 2, wherein the Druckplat is tenscanner 2 with a computer 3 for presetting the inking values associated.

Each color value for cyan, magenta, yellow and key comes from the computer into its own control unit 4 K, 4 Y, 4 M and 4 C. These control units 4 then control the ink application of the printing unit, each divided into color zones. For this reason, the control units 4 are also connected to a printing unit 5 . In the printing unit 5, the printing plates 1 are used for the printing plate scanner 2, a corresponding color application is performed on the printing plates on a web of paper 6 in the printing unit. 5 Individual pages 7 on the paper web 6 with color zones 7.1 can be seen in the drawing.

These color zones 7.1 are in turn picked up by a paper web or paper sheet scanner 8 , this scanner 8 being designed such that it can record the three primary colors red, green and blue separately from each other from a line 9 . For example, 5,000 values per color are determined per line 9 . If it is assumed that the total width of the paper web is 1,400 mm, the scanner 8 determines the color value of a 0.28 mm wide area. This determination is made safely while printing on the paper web. The scanner is designed so that the length of the individual color value range is integrated and the width is summed up. Thus, an entire color picture is taken of each color zone with the values for R, G and B.

The zonal RGB data from the scanner 8 correspond to the so-called actual data, ie they reflect the immediate color impression. These actual data are compared in the control unit 4 with the target data of the printing plates 1 .

A further expansion stage provides that the target data are not taken from the scanner data of the printing plates 1 , but from a scanner device 10 . Furthermore, one is. Combination of both embodiments possible.

The scanner device 10 is constructed similarly to the scanner 8 . However, it does not scan the printed product, but rather the so-called OK sheet or the print work approved by the customer. The scanner device 10 can also be expanded as a data input for the so-called proof function.

The color impression of the released page (sheet) is thus as the target value with the actual value of the paper web (paper sheet) compared directly.  

The advantage of this method is that it does not, as with the known methods, via a control strip / Kon troll surface indirectly, but the direct color impression as The target and actual values are recorded and the deviations from Minimize the differences in the color impression as Correction values for the ink fountain keys for Presetting and printing of the printing unit be used.

The colors determined by the scanner 8 and 10 are the remission colors R, G and B, which in turn are input to a computer 11 in which a conversion of the RGB color value (screen values) to CMYK color values (printing colors) takes place. The last-mentioned color values are then again entered into the control elements 4 K, 4 Y, 4 M and 4 C, so that they are used to correct the ink application on the corresponding ink roller and ink zone.

Item number list

1 pressure plate
2 scanners
3 computers
4 control unit
5 printing unit
6 paper web
7 page
7.1 Color zone
8 scanners
9 line
10 proofing facility.
11 computers

Claims (11)

1. A method for controlling a color application of a printing unit, into which printing plates are input, characterized in that color values of the entire color application after the printing unit are determined by a scanner, compared with target values and then control units for the color application are addressed. 2. The method according to claim 1, characterized in that the color values are summed up, integrated and in one Color space can be represented as a vector. 3. The method according to claim 1 or 2, characterized characterized in that the basic colors red, Green and blue can be determined. 4. The method according to claim 3, characterized in that the primary colors in primary colors cyan, magenta, yellow and Key converted and then addressed the control units become. 5. The method according to at least one of claims 1 to 4, characterized in that the color values in a proof Setup / function can be compared with target values. 6. The method according to at least one of claims 1 to 5, characterized in that the target values of different printing plates into one color vector in one any color space can be summarized and this with the actual color vectors compared and for control purposes is used.   7. The method according to claim 6, characterized in that the zone values of the printing plates CMYK to common Vectors can be combined in any color space. 8. Device for controlling an ink job of a printing unit ( 5 ), in which printing plates ( 1 ) are entered, characterized in that the inking rollers are assigned control elements ( 4 ) which, on the one hand, with a computer ( 3 ) for target values and, on the other hand, with are connected to a computer ( 11 ) for actual values and both the actual and the target values are based on the ink zone widths. 9. The device according to claim 8, characterized in that the determination of the target values and the determination of the actual values via a scanner ( 2 , 8 ). 10. The device according to claim 9, characterized in that the scanner ( 8 ) is designed so that it determines the three primary colors separately in one line. 11. The device according to claim 10, characterized in that the scanner ( 8 ) with a proofing device / function ( 10 ) is connected.