BEAM SCANNING LENS, BEAM SCANNING APPARATUS HAVING THE SAME, AND IMAGE FORMING APPARATUS

摘要

A beam scanning lens, a beam scanning apparatus having the same, and an image forming apparatus are provided to prevent generation of a defective image such as a color spreading by forming scanning lines on a surface of a photosensitive medium without a curve. If a refractive index distribution of a beam scanning lens formed by plastic molding is n(x), a space between a central axis of n(x) and a longitudinal central line of an effective area of the beam scanning lens widens as it goes away from the center of the beam scanning lens in a lengthwise direction. The space between the central axis of n(x) and the longitudinal central line of the effective area of the beam scanning lens is 0 at the lengthwise center of the beam scanning lens. The space between the central axis of n(x) and the longitudinal central line of the effective area of the beam scanning lens is changed from 0 to the thickness of the longitudinal center of beam scanning lens at the maximum level.