Patent ID: 7339713

Claim:
An optical beam scanner, comprising: a driving unit rotating a rotary polygon mirror that deflects and scans an optical beam onto an image supporter; a rotation position detection unit detecting a rotation position of the rotary polygon mirror; a rotation control unit controlling the driving unit in accordance with a rotation reference signal of the rotary polygon mirror and an output signal of the rotation position detection unit; an optical beam detection unit detecting the optical beam which is deflected and scanned by the rotary polygon mirror at a predetermined position on a scanning path so as to generate a horizontal synchronizing signal; a rotation reference signal generator generating a rotation reference signal of the rotary polygon mirror; a first timing generation unit generating a first reference timing so that the rotation reference signal generator generates the rotation reference signal to print a first surface of an object to be printed, said object including the first surface and a second surface; a second timing generation unit generating a second reference timing so that the rotation reference signal generator generates the rotation reference signal to print the second surface of the object; a timing measurement unit measuring a counter value generated by the first timing generation unit according to the horizontal synchronizing signal generated by the optical beam detection unit; and a phase control unit controlling a phase of the rotation reference signal to be supplied to the driving unit in accordance with the counter value obtained by the timing measurement unit.