Patent attributes
An image forming apparatus having: a plurality of scanners, each of the scanners having a rotary polygonal mirror; a position detecting section for generating an image start reference signal in a main scanning direction; a PLL control section for controlling a rotation number of the mirror on a basis of a reference frequency signal of the mirror and a pulse signal generated per one rotation of the mirror; and a phase control section for detecting phase difference of each mirror on the basis of the image start reference signal in the main scanning direction in the plurality of the scanners, controlling a phase of the reference frequency signal of each mirror, and correcting image deviation in a sub-scanning direction of an image formed by the plurality of the scanners. A control angle in which one rotation angle of the mirror is divided by a number of the pulse signal generated per one rotation of the mirror is equal to an integral multiple of a division angle in which one rotation angle of the mirror is divided by a number of mirror faces of the mirror.
