System, method and program for extracting invisible information

摘要

To enable extraction of invisible information even if visible information overlaps with invisible information. The present invention provides a method for extracting invisible information from an object in which visible information overlaps with at least part of invisible information formed in stealth ink. The method includes the steps of: irradiating the object with light for making the stealth ink luminous; receiving reflected light from the object; extracting image information from the received reflected light; splitting the image information into a plurality of pieces of color-channel information; obtaining a correlation function between the pixel values of at least two color-channel information selected from the plurality of pieces of color-channel information; reducing a visible information component of selected one of the plurality of pieces of color-channel information to thereby interpolate the color-channel information; and extracting invisible information from the interpolated one piece of color-channel information.