Patent ID: 8199392

Claim:
A light-scanning device comprising: a polygon scanner including a rotatable polygon mirror which deflects a laser beam emitted from a light source; an optical image-forming element which images the deflected laser beam on a predetermined position of an image carrier; an optical housing which supports the light source, the polygon scanner and the optical image-forming element; a cover disposed above the polygon mirror and configured to seal an opening of the optical housing; and a cylinder-shaped non-rotational shielding member disposed between the cover and the polygon mirror and attached to the cover so as to cover an upper part of the polygon mirror, wherein the non-rotational shielding member has an outer circumferential surface and is disposed on a circle that is concentric with a rotation center of the rotatable polygon mirror, wherein the non-rotational shielding member is disposed to surround an air space that is located between the polygon mirror and the shielding member, and wherein an outside diameter of the outer circumferential surface of the non-rotational shielding member is set to be larger than at least an inscribed circle of the rotatable polygon mirror.