Moire interference pattern reduction for scanning of half-toned images

Moire patterns are significantly suppressed in a scanner that continuously varies its number of lines per inch. The number of dots per inch in the direction different from the relative motion between the scanner and the document is generally a fixed property of the optical sensor, but in the LPI direction the distance between consecutive lines can be made to randomly vary between a maximum distance and a minimum distance. This spatially distributes the moire effect, and prevents its accumulation into the usual recognizable two dimensional pattern.