PURPOSE: To adjust positions of scanning lines accurately by utilizing the fact that ghost light from a rotary polygon mirror becomes standstill in principle, and detecting the displacement of the scanning lines and controlling the scanning lines to specific positions.
CONSTITUTION: The luminous flux L from a light source 2 after being reflected by a mirror surface 1a of the rotary polygon mirror 1 is passed through an image forming lens 3 and bent by an optical path bending mirror 6 to form its image at a point A in a scanned surface 4. Regularly deflected light L1 from the point A passes through optical paths shown by dotted lines and then forms the image at a point B on an oscillation detector 7. When the optical path bending mirror 6 rotates as shown by an arrow P by oscillations, a main scanning line moves as shown by an arrow Q, but the image formation position of the ghost light L2 also shifts as shown by an arrow R and its movement extent is detected by the oscillation detector 7. The position shift of the bending mirror 6 in the direction of the optical axis 0 of the image forming lens 3 is also detected.
USUI MASAYUKI
MINOURA KAZUO
BABA TAKESHI
Next Patent: OPTICAL BEAM DEFLECTING DEVICE