Image forming apparatus and scanning unit

A color image forming apparatus for forming color images on a recording medium by superposing images in a plurality of colors, the apparatus comprising:

• at least one photosensitive member comprising either a plurality of separate photosensitive members or a single photosensitive member having separate regions, the at least one photosensitive member being exposed by a plurality of light beams corresponding to the plurality of colors for forming latent images either on the plurality of separate photosensitive members or on the separate regions of the single photosensitive member, the at least one photosensitive member defining a main scanning direction;
• and
• a plurality of scanning lenses each provided for a corresponding one of the plurality of colors, each scanning lens transmitting a corresponding one of the plurality of light beams scanningly deflected in the main scanning direction for exposing the at least one photosensitive member to the light beams to form the latent images thereon, each scanning lens comprising:
• a lens body formed of resin and extending substantially in the main scanning direction, the lens body defining a sub-scanning direction perpendicular to the main scanning direction, the lens body having opposite surfaces both being substantially perpendicular to the sub-scanning direction;
• and
• a rib formed integrally with the lens body and protruding in the sub-scanning direction from either one of the opposite surfaces, the rib extending over a predetermined range in the main scanning direction.

A scanning unit comprising:

• a light emitting portion that emits a light beam;
• a deflector that scanningly deflects the light beam in a main scanning direction;
• a first scanning lens that converges the light beam with regard to the main scanning direction;
• and
• a second scanning lens that converges the light beam with regard to a sub-scanning direction perpendicular to the main scanning direction, the second scanning lens comprising:
• a lens body formed of resin and extending substantially in the main scanning direction, the lens body having opposite surfaces both being substantially perpendicular to the sub-scanning direction;
• and
• a rib formed integrally with the lens body and protruding in the sub-scanning direction from either one of the opposite surfaces, the rib extending over a predetermined range in the main scanning direction.