Media advance accuracy is an important parameter for any type of printer. Media advance concerns the media moving over a predetermined distance and/or at a predetermined speed, with respect to a print head, to allow the print head to print subsequent strokes on the media, in a controlled manner. A lack of accuracy in media advance may result in non-aligned print drops or strokes, and defects such as banding or grain. Media advance accuracy is important for every print technology. Print technologies include, but are not limited to, inkjet and laser driven print systems.
To improve media advance accuracy, the media drives of printers are oftentimes calibrated. This reduces the amount of error in the media drive, and as a consequence the banding and grain may be reduced. Such media drive calibration can be carried out at different moments, for example at the factory site, at the end of the manufacturing process, during installation at the customer site, or during a service operation, for example when replacing a component such as a main roller or an encoder disc.
A common calibration method involves printing specially arranged lines and/or fiducial marks on the media. After printing, the media is taken out of the printer and scanned by an external scanning tool to allow automatic processing of the printed lines and/or marks. From these lines and/or marks, information about the media advances can be derived. Subsequently the media drive can be calibrated, based on this information, to compensate for the errors that were detected.
A similar calibration method involves printing lines and/or marks, then taking the media from the printer, and placing it onto a print platen in transverse direction.
Then the printed plot is scanned by a line sensor that is present in the print head carriage.