Patent ID: 7385619
Filing Date: 2008-06-10
Classification: G02B

Abstract:
1. An image forming apparatus, comprising: an optical scanner, which emits a light beam in accordance with an image forming signal and deflects the light beam in a first direction; and a photosensitive drum, having an outer circumferential face adapted to be scanned by the deflected light beam to form a scanning line while being moved in a second direction perpendicular to the first direction, thereby forming a latent image thereon, wherein: in a case where a virtual scanned face is defined as a plane including the scanning line and orthogonal to an optical axis of the optical scanner, and a scanned face is defined as a tangential plane of the outer circumferential face including the scanning line, the optical scanner and the photoconductive drum are arranged such that: the shape of a beam spot formed by the light beam incident on the virtual scanned face is approximated to an ellipse; and the scanned face is inclined from the virtual scanned face about the scanning line with an inclined angle that depends on an inclined angle of a major axis of the ellipse from the second direction on the virtual scanned face, wherein: the latent image is for a monochrome image; a distortion level of a beam spot formed on the scanned face is defined by the following equation: where A represents a dimension in a direction of an inclination at +45 degrees relative to the first direction when an intensity of the beam spot becomes 17% of a peak intensity; B represents a dimension in a direction of an inclination at −45 degrees, relative to the first direction when an intensity of the beam spot becomes 17% of a peak intensity; and “min (A, B)” represents A or B which is smaller; and a difference between maximum and minimum values of the distortion level of the beam spot on the scanning line is not greater than 35%.