Patent ID: 6863457

Claim:
A lateral edge position detector for a recording medium including lateral edges extending in a first direction of feeding, said lateral edge position detector comprising: a movable lateral edge contact mechanism for being pressed by one of said lateral edges, to move away; an encoding panel for shifting together with said lateral edge contact mechanism, said encoding panel including plural slits arranged in a shifting direction at a regular pitch; an encoding sensor for optically detecting said slits moving past a detection region thereof, to output at least an A-phase pulse and a B-phase pulse that is deviated from said A-phase pulse by a half of said pitch; a counter for determining a direction of being up or down according to a phase difference between said A and B-phase pulses, and for counting said A and B-phase pulses, wherein a counted number of said counter represents a position of said one lateral edge in a width direction crosswise to said first direction.