Patent ID: 7524014

Claim:
An image forming method for forming an image on a print medium by use of an image forming apparatus including a print head that ejects a print recording liquid from a plurality of nozzles onto the print medium, a print head drive module that causes the print head to eject the print recording liquid from one of the nozzles, and a print recording liquid receiving area over which the print medium passes and which the print recording liquid ejected from the nozzles can reach, said image forming method comprising steps of: (a) generating a predetermined potential difference between the print recording liquid receiving area and the print head, and controlling the print head drive module so that the print head ejects the print recording liquid, which is charged in advance of ejection, from the nozzles to a specific area of the print recording liquid receiving area, which includes an exterior range outside an edge of the print medium and an interior range over the print medium, and then detecting electrical change in the print recording liquid receiving area or the print head; and (b) determining position of the edge of the print medium based on the electrical change detected in step (a).