Optical scanning device and image forming apparatus

An optical scanning device comprising:

• a light source unit;
• a light deflecting unit that deflects a light beam emitted from the light source unit;
• and
• a scanning optical device that focuses the light beam deflected by the light deflecting unit on a scanned surface,
• wherein the scanning optical device is provided in a direction in which there is a sound pressure level of a noise caused by rotation of a rotating polygon mirror included in the light deflecting unit, wherein
• when a direction parallel to a scanning direction of the light beam that passes through a rotation center of the rotating polygon mirror included in the light deflecting unit and scans the scanned surface is set as a Y axis;
• a direction that is perpendicular to a rotating shaft of the rotating polygon mirror is set as an X axis;
• two light shielding members provided such that at least a portion thereof is present in an area surrounded
• by a circumscribed circle of the rotating polygon mirror,
• by a first straight line that is perpendicular to the Y axis and is tangential to the circumscribed circle, and
• by a first optical axis of the light beam emitted from the light source unit
• are denoted by a first light shielding member and a second light shielding member;
• other two light shielding members provided such that at least a portion thereof is present in an area surrounded
• by the circumscribed circle of the rotating polygon mirror,
• by a second straight line that is perpendicular to the Y axis and is tangential to the circumscribed circle, and
• by a second optical axis of the light beam emitted from the light source unit and deflected by the light deflecting unit
• are denoted by a third light shielding member and a fourth light shielding member;
• a distance, in the X-axis direction, between the first light shielding member and the second light shielding member is denoted by L1;
• a distance, in the Y-axis direction, between the first light shielding member and the third light shielding member is denoted by L2;
• and
• a distance, in the Y-axis direction, between the second light shielding member and the fourth light shielding member is denoted by L3,
• one of a relation of L1<L2 and a relation of L1<L3 is satisfied.