Optical scanner and image forming apparatus

A curvature-adjustment device for an optical scanner, comprising:

• an optical beam emission unit configured to emit an optical beam;
• a deflection unit configured to deflect the optical beam in a main scanning direction;
• and
• a mirror configured to reflect the optical beam,
• the curvature-adjustment device configured to correct a curvature of a main scanning line on a surface of a scanning target and comprising:
• a support unit configured to support the mirror at an end thereof in a longitudinal direction of the mirror by contacting a rear surface of the mirror;
• an edge-positioned adjustment unit configured to curve the mirror by exerting a first force on the mirror perpendicular to a reflecting surface at a position different from a support position of the support unit with respect to the longitudinal direction of the mirror;
• a center-positioned adjustment unit configured to curve the mirror by exerting a second force on the mirror perpendicular to the reflecting surface in a direction opposite the direction of the first force provided by the edge-positioned adjustment unit at substantially a center of the mirror in the longitudinal direction of the mirror;
• and
• a fine adjustment unit configured to adjust a strength of the first force provided by the edge-positioned adjustment unit depending on a strength of the second force provided by the center-positioned adjustment unit.