Patent ID: 8184140
Filing Date: 2012-05-22
Classification: B41J,G03G

Abstract:
1. A line head comprising: first and second light emitting elements disposed in a first direction; and an optical system that images the light emitted from the first and second light emitting elements, wherein the optical system includes a rotationally symmetrical lens having a lens face including first and second regions that are defined by different definition expressions; the first region is formed to include an intersection point of the lens face with the symmetry axis of the rotationally symmetrical lens; the second region is formed to surround the periphery of the first region; and a first chief ray of a first light flux which is emitted from the first light emitting element and imaged by the optical system, a second chief ray of a second light flux that is emitted from the second light emitting element and imaged by the optical system, and the shape of the boundary portion between the first region and the second region of the lens face have the following relationship: wherein in the above formula, ω is a first direction angle that the first chief ray makes with the second chief ray, and Δθ is an angle that a tangent line to the first region at the boundary portion makes with a tangent line to the second region at the boundary portion in a first direction cross-section including the symmetry axis.