Folding Position Calibration via Pre-Fold Reference Mark

The patent applies the principle of color changes by forming a first image that is visually distinct from the surrounding region on the medium. This first image serves as a reference mark that creates a detectable difference between the side being measured and the overlapped side. When the medium is folded, the scanner can detect the position of the side by identifying the location of this distinct first image, thereby resolving the measurement difficulty when no natural difference exists between overlapping sides.

The patent applies preliminary action by forming the first image on the medium before the folding operation. This pre-formed reference image is positioned on the side that will be folded, allowing the scanning system to later detect and measure the folding position deviation by comparing the expected position of the first image with its actual position in the folded state.

The patent creates a visual distinction by forming a first image with different characteristics (such as density, color, or pattern) from the surrounding region. This distinct image serves as a permanent marker on the medium that preserves side position information through the folding process, allowing the scanning system to identify and measure the position of each side in the folded state.

The first image is formed on the medium in advance, before folding occurs. This preliminary marking ensures that the side position information is embedded in the medium itself, surviving the folding operation and enabling subsequent measurement without requiring additional complex marking steps during or after folding.