Patent ID: 7365765

Claim:
An apparatus for forming an image, comprising: a scanner motor rotatably driving a polygon mirror for optical scan; a laser light emitter emitting laser light toward the polygon mirror; a first-periodic-signal generator detecting the laser light reflected off from the polygon mirror, thereby generating a first periodic signal dependent on a scanning period of the laser light; a second-periodic-signal generator detecting directly or indirectly rotation of the scanner motor, thereby generating a second periodic signal dependent on a rotational speed of the polygon mirror; and a controller performing speed control of the scanner motor, based on at least one of the first periodic signal generated from the first-periodic-signal generator, and the second periodic signal generated from the second-periodic-signal generator, wherein the controller makes a first determination as to whether or not a pre-selected one of the first and the second periodic signal is abnormal, wherein the controller, upon the pre-selected signal being determined to be abnormal, makes a second determination as to whether or not a remaining one of the first and the second periodic signal is normal, and wherein the controller identifies at least one failed element of the apparatus, based on both the result of the second determination and the first determination that the pre-selected signal is abnormal.