IMAGE FORMATION OPTICAL SCANNER, IMAGE FORMING APPARATUS, AND NON-TRANSITORY COMPUTER-READABLE RECORDING MEDIUM STORING IMAGE FORMING APPARATUS OPTICAL SCANNING PROGRAM

An optical scanner includes a light source; a rotating polygon mirror that reflects and deflects the light beam output from the light source; a drive unit that rotationally drives the rotating polygon mirror; a beam detection unit that detects the light beam; and a control unit that controls the light source and the drive unit. The control unit can control the drive unit with a detection result of the beam detection unit, and adjust a rotational speed of the rotating polygon mirror. The control unit has a high definition mode in which the rotational speed of the rotating polygon mirror is controlled with high accuracy at the time of normal light beam irradiation, and a light source life mitigation mode in which light beam irradiation is performed by controlling the output of the light source with keeping rotation of the rotating polygon mirror during standby.