Patent ID: 6431775
Filing Date: 2002-08-13
Classification: B41J

Abstract:
An automatic offset error correction system for a bidirectional printing device, comprising:a bidirectional printer having a cartridge mounted on a movable carriage, which is driven by a microstepping motor to glide along tracks and to print on media beneath the cartridge in both a forward direction and a backward direction, said microstepping motor having a microstepping characteristic, which subdivides individual optically measurable steps into multiple microsteps with time division, a sensor having a radiation source and a radiation detector to sense the actual position of the cartridge corresponding to one of said microsteps during printing in both said forward direction and said backward direction, a shutter, which blocks the radiation from said source to said detector when the shutter glides past the sensor, a print controller, which receives the signal from said sensor, calculates positional offset between printing in the forward direction and printing in the backward direction, and controls the microstepping motor to automatically adjust the cartridge to compensate said position offset during printing.