US Patent 7889221 Optical scanning apparatus

An optical scanning apparatus forms a latent image by scanning a laser beam emitted from a light source on an image bearing member. The apparatus includes first and second laser beam detectors for detecting the laser beam and a scanning-line slope detector for detecting a slope of a scanning line on the image bearing member on the basis of the result of detection obtained by the first and second laser beam detectors. The first laser beam detector detects the laser beam in a scanning area in front of an area in which the latent image is formed on the image bearing member and the second laser beam detector detects the laser beam in a scanning area behind the area in which the latent image is formed on the image bearing member.