Optical scanning device and image forming apparatus using the same

An optical scanning device, comprising:

• a light source device;
• a deflecting device having a deflecting surface;
• an input optical system configured to direct a light beam from said light source device to the deflecting surface of said deflecting device;
• an imaging optical system configured to image a light beam scanningly deflected by the deflecting surface of said deflecting device, upon a surface to be scanned;
• and
• a light blocking member configured to block ghost light and disposed on a light path between the deflecting surface and the surface to be scanned;
• wherein, in a sub-scan section, the light beam to be incident on the deflecting surface of said deflecting device is incident thereon from an oblique direction with respect to an optical axis of said imaging optical system,
• wherein, in the main-scan section, the shape of said light blocking member is arcuate about a center of a circle which is taken at an axial deflection point of the light beam incident on the deflecting surface of said deflecting device, at an arbitrary position Y in the main-scan direction, such that the distance from the light blocking member to the deflecting device decreases from the center of the light blocking member to the ends of the light blocking member in the main-scan direction,
• wherein with respect to the sub-scan direction, a top end portion and a bottom end portion of said light blocking member are linear in parallel with the main scan direction as seen from the deflecting device, and
• wherein all imaging optical elements which constitute said imaging optical system and which are disposed between said deflecting device and said light blocking member have no refracting power in the sub-scan direction.