Color printer for repetitively printing a document

摘要

The present invention discloses a color printer and its printing method for accurately printing different colors on a document. The printer comprises two roller wheels for clamping and carrying the document forward and backward, a stepping motor for driving the two roller wheels, a detector for detecting a front edge of the document, a printing head for printing the document, and a control circuit for controlling operations of the printer. The control circuit comprises a memory for recording the number of steps of the stepping motor as printing position of the document. The printing method comprises the following steps: (1) using the stepping motor to carry the document forward and using the detector to detect the front edge of the document; (2) calculating the number of forward steps of the stepping motor after the front edge of the document is detected and using the printing head to print the document according to the calculated forward steps until one pass of the printing is finished; (3) carrying the document backward to move the front edge of the document away from the detector; and (4) repeating from step (1) to step (3) until all passes of the printing are finished.