Electronic device and image forming apparatus

An image forming apparatus comprising:

• a photosensitive member;
• a polygon motor;
• a polygon mirror configured to be rotatably driven by the polygon motor for scanning a laser beam over the photosensitive member;
• a detector that detects a rotational speed of the polygon motor;
• and
• a controller that selects a gain from a plurality of gains based on the rotational speed and that controls rotation of the polygon motor through feedback control,
• wherein the controller uses a first gain from startup of the polygon motor until the polygon motor initially reaches a first rotational speed after the startup;
• is wherein the controller switches to a second gain smaller than the first gain when the polygon motor initially reaches the first rotational speed after the startup, and uses the second gain in a predetermined range with respect to the rotational speed, the predetermined range being defined between a lower limit smaller than the first rotational speed and a higher limit larger than the first rotational speed;
• and
• wherein an image formation on the photosensitive member with the laser beam is started after the polygon motor initially reaches the first rotational speed after the startup.