Abstract: A method for detecting printing nozzle errors in an inkjet printing machine provides a high degree of robustness in the detection of errors by printing a nozzle test pattern in the inkjet printing machine. The test pattern is then digitalized by using a camera and transmitted to a computer for evaluation. There, the recorded test pattern is investigated by using methods of digital image processing, such as a Fourier analysis, and evaluated in the frequency range with regard to specific anticipated printing nozzle errors. Specific printing nozzle errors can be detected especially on the basis of amplitude, phase and variance errors in the signal in the frequency range. Moreover, by using the phase error, it is possible to evaluate whether the two print heads are disposed in an incorrect adjustment position relative to one another by calculating displacements of the phase error in transition regions of two print heads.

Abstract: A method for detecting and compensating for failed printing nozzles in an inkjet printing machine by using a computer, includes printing a current print image, recording the printed print image by using an image sensor and digitizing the recorded print image by using the computer, adding digitized color values of the recorded print image of every column over the entire print image height and dividing the added-up color values by the number of pixels to obtain a column profile, subtracting an optimized column profile without failed printing nozzles from the original column profile to obtain a differential column profile, setting a maximum value threshold defining a failed printing nozzle when exceeded, applying that maximum value threshold to the differential column profile to obtain a resultant column profile every maximum of which marks a failed printing nozzle. The marked printing nozzles are compensated in a subsequent printing operation.

Abstract: A method for detecting and compensating for failed printing nozzles in an inkjet printing machine by using a computer, includes printing a current print image, recording the printed print image by using an image sensor and digitizing the recorded print image by using the computer, adding digitized color values of the recorded print image of every column over the entire print image height and dividing the added-up color values by the number of pixels to obtain a column profile, subtracting an optimized column profile without failed printing nozzles from the original column profile to obtain a differential column profile, setting a maximum value threshold defining a failed printing nozzle when exceeded, applying that maximum value threshold to the differential column profile to obtain a resultant column profile every maximum of which marks a failed printing nozzle. The marked printing nozzles are compensated in a subsequent printing operation.

Abstract: A method for detecting printing nozzle errors in an inkjet printing machine provides a high degree of robustness in the detection of errors by printing a nozzle test pattern in the inkjet printing machine. The test pattern is then digitalized by using a camera and transmitted to a computer for evaluation. There, the recorded test pattern is investigated by using methods of digital image processing, such as a Fourier analysis, and evaluated in the frequency range with regard to specific anticipated printing nozzle errors. Specific printing nozzle errors can be detected especially on the basis of amplitude, phase and variance errors in the signal in the frequency range. Moreover, by using the phase error, it is possible to evaluate whether the two print heads are disposed in an incorrect adjustment position relative to one another by calculating displacements of the phase error in transition regions of two print heads.

Abstract: A color measurement on printed materials produced by a printing press is performed by at least a first color measuring device installed in the printing press and at least a second color measuring device. A signal is output by the first color measuring device in the printing press when the measured color values registered on the printing materials are located within a predefined tolerance limit for a predefined period and that, after the signal has been output, a color measurement on one of the printed materials thus produced is performed with the second color measuring device.

Abstract: An apparatus in a machine for processing printing material has a register sensor for register measurement between at least two color separations of a printed image printed above one another on a printing material. The register sensor registers optically deviations between the two color separations and forwards the deviations onto a computer. The register sensor contains at least one photodiode having at least two quadrants. The largely rectangular evaluation areas of the photodiode are aligned obliquely in relation to the edges of the conveyed printing material. A register mark to be detected by the register sensor has a plurality of wedge-shaped colored areas pointing in a peripheral direction of the printing material, one of the wedge-shaped colored areas being a reference color used as a reference variable and others of the wedge-shaped colored areas being register colors to be controlled.

Abstract: A method for the correction of measurement errors caused by surface effects induced by ink splitting during the color measurement of a printed sheet on a running printing device, includes scanning the printed sheet photoelectrically point by point and forming color and/or density measured values from scanning signals from the scanned points. Those scanned points which have a brightness exceeding a limiting value are identified, and the measured values are corrected by using the identified scanned points. In particular, during the formation of the color and/or density measured values, the scanning signals from the identified scanned points are not taken into account.

Abstract: A method for color control in printing presses having at least one first color measuring instrument and at least one second color measuring instrument, includes registering at least one first inking zone on a printing material with the first color measuring instrument and registering at least one other, second inking zone on the printing material with the second color measuring instrument. In a first step, a color difference between actual colorations of the first and second inking zones is calculated, in a second step, a color difference between an actual coloration of the first inking zone and a desired coloration of the second inking zone is calculated and, in a further step, the calculated color differences are added and supplied to a color control for the second inking zone.

Abstract: An apparatus in a machine for processing printing material has a register sensor for register measurement between at least two color separations of a printed image printed above one another on a printing material. The register sensor registers optically deviations between the two color separations and forwards the deviations onto a computer. The register sensor contains at least one photodiode having at least two quadrants. The largely rectangular evaluation areas of the photodiode are aligned obliquely in relation to the edges of the conveyed printing material. A register mark to be detected by the register sensor has a plurality of wedge-shaped colored areas pointing in a peripheral direction of the printing material, one of the wedge-shaped colored areas being a reference color used as a reference variable and others of the wedge-shaped colored areas being register colors to be controlled.

Abstract: An apparatus in a machine for processing printing material has a register sensor for register measurement between at least two color separations of a printed image printed above one another on a printing material. The register sensor registers optically deviations between two color separations lying one above the other on the printing material and forwards the deviations onto a computer. The apparatus includes register marks to be measured by the apparatus. The apparatus is distinguished in that the register sensor contains at least one photodiode having at least two quadrants, and in that the largely rectangular evaluation areas of the photodiode are aligned obliquely in relation to the edges of the conveyed printing material.

Abstract: In a method for determining color and/or density values for use in monitoring and regulating a printing process in a printing apparatus, specifically in a sheet-fed offset printing press, measuring areas of a printed sheet are measured photoelectrically during the printing process, directly in or on the running printing apparatus. From the measured values obtained in the process, the color and/or density values for the relevant measuring areas are formed. From the measurement, measured value deviations caused directly in the printing process with respect to a measurement outside the printing process can be corrected computationally.

Abstract: A method for the correction of measurement errors caused by surface effects induced by ink splitting during the color measurement of a printed sheet on a running printing device, includes scanning the printed sheet photoelectrically point by point and forming color and/or density measured values from scanning signals from the scanned points. Those scanned points which have a brightness exceeding a limiting value are identified, and the measured values are corrected by using the identified scanned points. In particular, during the formation of the color and/or density measured values, the scanning signals from the identified scanned points are not taken into account.

Abstract: Spectral, densitometric, or color measured values are detected on sheet printing materials during the printing process in a sheet-fed printing press. The measured values are determined on sheets as they are moving through the printing press and the measured values are used in real-time by a computer to control parameters for controlling the printing process in the sheet-fed printing press.

Abstract: A printing press for processing sheet printing materials includes at least one printing unit, a computer and a measuring device for monitoring printing quality during a printing process. The measuring device has a sensing device for measuring by color or spectrally to register the printing material. At least one sheet-guiding element leads the sheet printing material past the sensing device. A measuring device for monitoring printing quality during a printing process in a printing press for processing sheet printing materials, is also provided.

Abstract: A color measurement on printed materials produced by a printing press is performed by at least a first color measuring device installed in the printing press and at least a second color measuring device. A signal is output by the first color measuring device in the printing press when the measured color values registered on the printing materials are located within a predefined tolerance limit for a predefined period and that, after the signal has been output, a color measurement on one of the printed materials thus produced is performed with the second color measuring device.

Abstract: An apparatus and a method for exchanging information about tonal values and calorimetric values between a prepress stage, a printing stage and a quality control stage are provided. The apparatus and the method create characteristic curves which are used to optimize a process calibration and a color calibration.

Abstract: A printing press for processing sheet printing materials includes at least one printing unit, a computer and a measuring device for monitoring printing quality during a printing process. The measuring device has a sensing device for measuring by color or spectrally to register the printing material. At least one sheet-guiding element leads the sheet printing material past the sensing device. A measuring device for monitoring printing quality during a printing process in a printing press for processing sheet printing materials, is also provided.

Abstract: In a method for determining color and/or density values for use in monitoring and regulating a printing process in a printing apparatus, specifically in a sheet-fed offset printing press, measuring areas of a printed sheet are measured photoelectrically during the printing process, directly in or on the running printing apparatus. From the measured values obtained in the process, the color and/or density values for the relevant measuring areas are formed. From the measurement, measured value deviations caused directly in the printing process with respect to a measurement outside the printing process can be corrected computationally.

Abstract: Spectral, densitometric, or color measured values are detected on sheet printing materials during the printing process in a sheet-fed printing press. The measured values are determined on sheets as they are moving through the printing press and the measured values are used in real-time by a computer to control parameters for controlling the printing process in the sheet-fed printing press.

Abstract: An apparatus in a machine for processing printing material has a register sensor for register measurement between at least two color separations of a printed image printed above one another on a printing material. The register sensor registers optically deviations between two color separations lying one above the other on the printing material and forwards the deviations onto a computer. The apparatus includes register marks to be measured by the apparatus. The apparatus is distinguished in that the register sensor contains at least one photodiode having at least two quadrants, and in that the largely rectangular evaluation areas of the photodiode are aligned obliquely in relation to the edges of the conveyed printing material.