Optical scanning apparatus and image forming apparatus using the same

摘要

The present invention provides a high-performance and compact overfilled optical scanning apparatus and an image forming apparatus using the same. In an optical scanning apparatus having an incidence optical system for causing a light beam emitted from light source unit to be incident on the deflection surface of a light deflector having a plurality of deflection surfaces, in a converged state with a light beam width in a main scanning section wider than that of the deflection surface, and an imaging optical system for imaging the light beam reflected and deflected by the light deflector on a surface to be scanned, and for forming an image on the surface to be scanned, each element is appropriately set to satisfy the conditional expression, $\left(1-\frac{\mathrm{Sk}}{f}\right)\mathrm{delta}L\left[\sin \left(\frac{\mathrm{alpha}}{2}-\frac{\mathrm{beta}}{2}\right)+\cos \left(\frac{\mathrm{alpha}}{2}-\frac{\mathrm{beta}}{2}\right)\tan \mathrm{beta}\right]<\frac{25.4}{3N_M},$ where f is the focal length of the imaging optical system in a main scanning direction, Sk is the distance in the main scanning section from the rear principal plane position of the imaging optical system to an imaging point of the converged light beam, alpha and beta are angles in the main scanning section formed by the optical axis of the imaging optical system and the principal ray of the light beams incident on and reflected by the light deflector, respectively, deltaL is the unevenness of distances in the main scanning section from the rotation center of the light deflector to the deflection surfaces, and N_M is the number of pixels per one inch in the main scanning direction on the surface to be scanned.