Image Forming Apparatus

An image forming apparatus, comprising:

• a deflecting means, comprising a rotational axis and at least two-staged polygon mirrors circumferentially located on the rotational axis at shifted angles in a rotational direction thereof, configured to reflect a light beam entering each of the polygon mirrors while deflecting the light beam to scan plural image bearers;
• a dividing means configured to divide the light beam from a light source into at least two light beams to enter the polygon mirrors at different stages, respectively;
• a light receiving means configured to detect the light beam reflected from the deflector;
• a detecting means configured to detect timings of the two-staged polygon minors to scan, based on a light beam detection interval detected by the light receiver;
• and
• a light shutting means configured to shut a light beam entering an unused image bearer among the plural image bearers during a period when the light source lights up before the detector detects the timings.