Patent ID: 8310738

Claim:
A scanning optical device comprising: a rotating polygonal mirror provided with a plurality of reflecting faces that reflect an incident light beam while the rotating polygonal mirror is rotated; a first light source which emits a first light beam from one section obtained by sectioning said scanning optical device with a plane passing through the rotation axis of said rotating polygonal mirror; a second light source which emits a second light beam from the other section obtained by the sectioning with said plane; an imaging unit which images the first and second light beams having been deflected/scanned by said rotating polygonal mirror onto corresponding photosensitive members; a first detection unit which detects the first light beam on the scanning start side in the main scanning direction; a second detection unit which detects the first light beam on the scanning end side in the main scanning direction; a third detection unit which detects the second light beam on the scanning start side in the main scanning direction; a fourth detection unit which detects the second light beam on the scanning end side in the main scanning direction; a first calculation unit which calculates a time interval between the time when the first light beam is detected by said first detection unit and the time when the first light beam is detected by said second detection unit as a scan time of said first light source; a second calculation unit which calculates a time interval between the time when the second light beam is detected by said third detection unit and the time when the second light beam is detected by said fourth detection unit as a scan time of said second light source; a storage unit which stores the scan times for said respective reflecting faces of said rotating polygonal mirror calculated by said first calculation unit and said second calculation unit; and a jitter correction unit which corrects jitter by controlling a pixel clock supplied to said first light source in accordance with the scan time of said second light source, and a pixel clock supplied to said second light source in accordance with the scan time of said first light source.