Optical scanning device and image forming apparatus incorporating the same

An optical scanning device comprising:

• a first light source portion that emits a first light beam;
• a second light source portion that emits a second light beam;
• a scanning optical system that directs the first and second light beams to scan corresponding image carrying members;
• and
• a housing that holds the first and second light source portions and optical components constituting the scanning optical system,
• the optical scanning device shining light to surfaces of the image carrying members to form electrostatic latent images through attenuation of electric charge,
• wherein
• the scanning optical system includes:
• a polygon mirror that deflects the first and second light beams;
• one or more scanning lenses that deflect the first and second light beams deflected by the polygon mirror;
• and
• a plurality of turn-back mirrors that direct the first and second light beams deflected by the scanning lenses to the surfaces of the image carrying members,
• the turn-back mirrors include:
• a first mirror that reflects the first and second light beams having passed through the scanning lenses;
• a second mirror that directs the first light beam reflected by the first mirror to one of the image carrying members;
• and
• a third mirror and a fourth mirror that direct the second light beam reflected by the first mirror to another of the image carrying members, and
• the second and third mirrors are disposed, as seen from a main scanning direction, closer to the polygon mirror than the first mirror, and the fourth mirror is disposed, as seen from the main scanning direction, farther from the polygon mirror than the first mirror.