Patent ID: 8998372
Filing Date: 2015-04-07
Classification: G03G

Abstract:
1. A scanning optical apparatus comprising: a light source; a polygon mirror including a plurality of reflecting surfaces that reflect a light beam emitted from the light source, and configured to move the reflecting surfaces to deflect the light beam emitted from the light source, so as to scan a surface to be scanned in a main scanning direction; a first sensor that receives the light beam reflected by the reflecting surfaces of the polygon mirror; a second sensor located inside the light source so as to intersect the optical axis of the light beam at a position opposite to an emission outlet of the light beam, the second sensor being receives the light beam reflected by the reflecting surface and detects intensity of the light beam received; a light beam detection unit that compares between an output value of the first sensor and a predetermined first threshold, to thereby decide that the light beam reflected by the reflecting surface has entered the first sensor when the output value of the first sensor is equal to or higher than the first threshold, and that the light beam reflected by the reflecting surface has not entered the first sensor when the output value of the first sensor is lower than the first threshold; a reference signal generation unit that generates a scan start reference signal for starting scanning of the surface to be scanned with the light beam deflected by the reflecting surface, when the light beam detection unit detects that the light beam has entered the first sensor; and a returned light detection unit that compares between an output value of the second sensor and a second threshold corresponding to light beam intensity higher than the intensity of the light beam reflected by the reflecting surface and corresponding to the first threshold, to thereby decide that the light beam reflected by the reflecting surface has entered the second sensor when the output value of the second sensor is equal to or higher than the second threshold, and that the light beam reflected by the reflecting surface has not entered the second sensor when the output value of the second sensor is lower than the second threshold.