or patches in a single direction across the substrate stripe processing is performed on a tile by tile basis for each tile distortion compensation is performed followed by pixel to pixel comparison the cad data signals form the reference or master tiles and are configured not to overlap scan tile signals share the same x center with their corresponding cad tiles but overlap in the x direction to accommodate shifting from the nominal the stripe length is extended in the preferred embodiment by 16 pixels at the beginning and end to allow shifting from the nominal position for the first and final tile the preferred embodiment is configured to determine the distortion during the scan of the substrate although distortion could be equivalently determined during a prescan distortion compensation is performed either in a 34 learn 34 mode where distortion is computed only for a first substrate or panel in a lot data form the first substrate are stored and reused for the lot remainder alternatively distortion compensation can be performed for each or only some substrates in a given lot operating mode is manually selectable while the system is functioning the overall operation of the present compensation system is shown diagramatically in fig6 algorithm 62 is executed for.