Scanning optical device and image forming apparatus

A scanning optical device for scanning an object to be scanned with a laser light, said scanning optical device comprising:

• a light source constituted to emit the laser light;
• a deflection unit constituted to deflect the laser light emitted from said light source;
• a reflecting mirror constituted to reflect the laser light deflected by said deflection unit to guide to the object to be scanned;
• a housing constituted to accommodate said deflection unit and said reflecting mirror;
• a cover constituted to cover an opening of said housing;
• and
• an elastic member constituted to urge said reflecting mirror toward said housing,
• wherein said reflecting mirror includes a first surface urged by said elastic member, a second surface opposite to said first surface, a third surface substantially perpendicular to said first surface and said second surface, in parallel with a longitudinal direction of said reflecting mirror and closer to said opening of said housing, and fourth surface opposite to said third surface, and
• wherein said housing includes a bearing surface constituted to support said second surface, and said cover includes a regulating portion constituted to regulate movement of said reflecting mirror to a mirror widthwise direction, substantially perpendicular to the longitudinal direction and substantially parallel with said second surface, and toward the opening of said housing, said regulating portion being provided opposite to only a part of said third surface so that a ridge line of said reflecting mirror between said second surface and said third surface does not contact said regulating member even an attitude of said reflecting mirror changes in a direction away from said bearing surface when said reflecting mirror is viewed in the longitudinal direction.