DD301438A7 - METHOD FOR DETERMINING THE PRINTING FLUORESCENT PART OF PRINTING MACHINES - Google Patents

Abstract

The invention relates to a method for determining the printing area fraction for printing presses. The object of the invention is to provide a measuring method which provides more accurate measurement results and extends the field of application. The object, therefore, is to reduce the effects of irregularities occurring on the surface of the original and to eliminate the need for the presence of calibration standards. The object is achieved in that an area of known area coverage outside the print image area per sensor is measured and stored, a measurement of the same, lying outside the print image area area or the measuring point performed with an additional filtering and the measured value is stored during or after the pointwise measurements in each color zone width column of the printed image area, the normalization of the measured values on the filter transmission curve and then determines the position of the point in the print image area with the extreme degree of blackening and the average of all normalized measured values for the respective color zone width column and stored, the area coverage of this point determined and From the stored values, the areal coverage per column and from that the color preset values are obtained.

Description

Field of application of the invention

The invention relates to a method for determining the percentage printing surface portion of the respective color zone width columns of templates such as printing plates.

Characteristic of the known technical solutions

It is known from DE-OS 3029273 a device for measuring the printed image area of an offset printing plate, with which the printing plate is optically scanned.

For each printing plate, a calibration is performed and the printed image area of the printing area determined according to the type of the respective printing plate. The calibration of the detector device provided for the optical scanning is carried out by means of a calibration mark. By sampling this mark before starting the measurement, an absolute comparison value for a be; Taken percentage area coverage according to the type of printing plates won. A disadvantage is that the accuracy is affected by the small proportion of Meßmarkfläche on the surface of the entire printing plate. Errors on the surface of the printing plate can lead to inaccurate measurement results. Also, according to EP-PS 0.095.606, a method and an apparatus for determining the area coverage of a printing plate become known, after which each individual sensor is calibrated prior to the measurement based on calibration strips, each with minimum and maximum area coverage. The calibration strips are arranged over the entire width of the pressure plate. The adaptation of the sensors to the printing plate or printing plate specific conditions via one or more sensors or via an additional sensor. This correction calibration and tuning is performed within a gauge and calibration area located on the artwork.

A disadvantage of this solution is the necessity of attaching space-consuming calibration strips on the printing original or plate and associated limitation of the Finsatzes of the device or the method for printing originals or plates with calibration strips.

Object of the invention

The aim of the invention is to provide a method for determining the printing area proportion, which provides more accurate measurement results and extends the field of application of such methods.

-2- 301438 Explanation of the essence of the invention

The object of the invention is to provide such a method, with the influences reduced by occurring irregularities on the surface of the template and requires no calibration standards on the template. The technical problem is solved in that an area of known area coverage outside the print image area per sensor is measured and stored, a measurement of the same, outside the print image area lying surface or the measuring point is performed with an additional filtering and the largest value is stored, the difference values of The values measured and measured at the same measuring point are formed and stored during and after the pointwise measurements in each color zone width column of the printed image area, the normalization of the measured values to the filter transmission curve and then the position of the dot in the printed image area with the extreme degree of blackening and the mean values all normalized measured values for the respective color zone width column are determined and stored, the value of the areal coverage of the point with the extreme degree of blackening is measured or specified and the normi mean values are converted by means of the stored difference values of the assigned sensors and the area coverage of the point with the greatest degree of blackening to values of the area coverage per column and to Farbvoreinstellwerten. Advantageously, the method is designed so that a pressure-free surface measured outside the print image area and the largest remission value and its position is stored. By erfindungsgsmäße method, the working characteristics of the sensors, different templates, especially printing plates and irregularities on the surface are detected, without requiring special calibration standards. The method is equally applicable to templates and printing plates without and with calibration standards.

embodiment

The invention will be explained in more detail with reference to an embodiment. The first step of the measuring method according to the invention, for example, is the scanning of a print-free edge in the printing plate during the transport of the detector device to the printed image area. The measurements are carried out by all sensors. The largest value (remission value) of all measured values per sensor as well as the position of its measuring point is determined and stored in a computer. It represents the measuring location with 0% area coverage.

Thereafter, as a second step, the sensors are again transported to the print image area and the reflectance value is measured at the determined positions with an additional filter of known permeability. It is also possible to measure the entire area with additional filter again and to save each the largest value.

In the third method step, the difference value of the respectively measured values without filter and with filter is formed, and one thus obtains the curve increase of the working characteristic of the respective sensor. The difference values are also saved.

In the print image area, each color / ones width column is measured point by point and each measured value normalized to the Filtsrtransmissionskurve. However, this fourth method step can also be carried out so that first all measured values are stored and then the standardization is carried out. Within this process step, after normalization, the position of the point with the greatest degree of blackening is determined and the column-wise mean values of the normalized values are formed.

In the subsequent method step, the specific areal coverage is measured at the measuring point with the greatest degree of blackening or, if known, given.

The final process step includes the evaluation of all measured, determined and stored values. By means of the stored differential values (curve increase values of the sensors) and the areal coverage of the point with the greatest degree of blackening, the normalized average values of the color zone widths columns are converted into concrete areal coverage degrees.

From these values, the color preset values are then determined in a known manner.

Claims (2)

1. A method for determining the printing area ratio for printing machines by optical scanning of templates and calibration of the sensors for each template, characterized in that a) an area of known area coverage outside the printed image area per sensor is measured and stored, b) introducing a measurement of the same area or measuring point outside the printed image area with additional filtering and storing the measured value, c) the difference values of the values measured in each case at the same measuring point by the two measuring operations are formed and stored, d) the normalization of the measured values to the filter transmission curve takes place during or after the pointwise measurements in each color zone width column of the printed image area and then the position of the point in the printed image area with the extreme degree of blackening and the average of all normalized measured values for the respective color zone wide column are determined and stored, e) the value of the area coverage of the point with the extreme degree of blackening is measured or specified f) and the normalized mean values are converted by means of the stored difference values of the assigned sensors and the areal coverage of the point with the extreme degree of blackening to values of the areal coverage per column and to color preset values. 2. The method according to item 1, characterized in that a pressure-free surface measured outside the printed image area and the largest remission value and its position is stored.