Automated image sensor calibration

A method for calibrating image sensors and adjusting print heads in an inkjet printing machine in an automated way via a computer, which comprises the steps of:

• printing a test print chart containing filled circular discs functioning as calibration dots, the filled circular discs having a minimum diameter that is selected in a way for them to function in an optimal way even if defective printing nozzles occur;
• recording the test print chart by means of at least one image sensor to create a digital image;
• determining a coordinate transformation between coordinates on the test print chart and coordinates of the at least one image sensor and the print heads via the computer;
• implementing a computer-assisted evaluation process of the digital image to determine the coordinates on the test print chart;
• deriving correction values for print head adjustment and camera at least one image sensor calibration from results of the coordinate transformation and/or a comparison thereof with determined measured values of the test print chart by means of the computer;
• implementing the print head adjustment and the at least one image sensor calibration by means of the computer and using the correction values;
• and
• subdividing a printing substrate region to be printed and recorded by the at least one image sensor into image sensor regions corresponding to a number of the image sensors that are used, every one of the image sensor regions include a reference dot in a form of a filled circular disc printed centrally above the calibration dots, the reference dot being used for referencing within an individual image sensor region of the image sensor regions.