Patent ID: 6888655

Claim:
An optical beam scanning device comprising: optical beam scanning means for rotational polygonal mirror to deflect entering luminous flux and scan an object to be scanned with the luminous flux; pre-deflection optical system which shapes a luminous flux emitted from light source means so that the optical beam scanning means images the resultant luminous flux as a long line image in a direction corresponding to a main scanning direction; and imaging optical system which images the luminous flux scanned by the optical beam scanning means onto the object to be scanned, wherein the imaging optical system comprises an imaging optical element that in the entire main scanning area for luminous flux to be scanned by the optical beam scanning means, the central scanning position has a main scanning direction curvature different from that of the scanning end, and a scanning angle Î± 0 [rad] at which the optical beam scanning means scans the object to be scanned with the luminous flux is defined by the following expression, Î± 0 â‰¦Ï€{(2 /N )âˆ’( Vr /3)Ã—10 âˆ’7 } wherein N indicates the number of surfaces of the rotational polygonal mirror and Vr [r.p.m.] indicates the revolution of the rotational polygonal mirror.