Patent ID: 7131782

Claim:
A paper edge sensing apparatus in a printer having a pickup unit and a convey unit, the apparatus comprising: a carrier; a printer head mounted to the carrier; a first paper sensor mounted between the pickup unit and the convey unit to detect a top edge and a bottom edge of a paper; a second paper sensor mounted to the carrier a predetermined distance from the printer head, to detect a right edge, a left edge, the top edge, and the bottom edge of the paper; and a controller controlling operations of the printer head to control print margins of top and bottom ends of the paper by comparing first top edge and first bottom edge signals from the first paper sensor and second top edge and second bottom edge signals from the second paper sensor, and to control print margins of right and left edges of the paper according to left and right edge detections signals of the second paper sensor, wherein the controller determines a print start timing as a later of an estimated timing of the top edge reaching a print position proximate to the printer head based on the first top edge signal and a speed of the paper moving through the printer, or the second top edge signal.