Optical scanning device and image forming apparatus

An optical scanning device comprising:

• a light source configured to emit a laser light;
• a deflecting unit configured to deflect the laser light;
• an optical member group configured to image the laser light, deflected and scanned by the deflecting unit, to a scanned member;
• a casing in which the deflecting unit and the optical member group are accommodated, the casing including an opening through which the laser light passes;
• and
• a light transmissive member configured to cover the opening,
• wherein the light transmissive member includes a base surface and a plurality of projected portions provided on the base surface, and
• wherein when a distance between a center portion of one of the projected portions and a center portion of the projected portion adjacent to the one of the projected portions with respect to a longitudinal direction of the light transmissive member is defined as an interval between the projected portions,
• a height of the projected portions from the base surface is larger than the interval.