Optical scanning device and image forming apparatus including same

An optical scanning device comprising:

• an optical source unit for emitting a laser beam;
• a polygon mirror configured to rotate about a rotation axis extending and reflects the laser beam emitted from the optical source unit, so as to scan a circumferential surface of an image carrier in a main scanning direction;
• and
• a casing configured to house the polygon mirror, wherein
• the casing includes a bottom wall portion extending in a direction crossing the rotation axis of the polygon mirror, and a peripheral wall portion protruding from a periphery of the bottom wall portion so as to surround the polygon mirror from outside in a radial direction,
• the optical source unit includes a laser diode having a plurality of light emission points for emitting the laser beams, and is fixed to an outer circumferential surface of the peripheral wall portion, and a circuit board having a mounting hole for inserting terminals of the laser diode extending in a direction opposite to the laser beam emitting direction,
• the peripheral wall portion includes a guide member protruding from the outer circumferential surface, so as to be inserted in a board insertion hole formed in the circuit board, and
• a distal end of the guide member is positioned on an opposite side of the laser beam emitting direction with respect to a distal end of the laser diode terminal.