| 摘要 |
PURPOSE:To miniaturize an optical system by varying the power in the direction for which there is available a surface inclination correcting function of a lens positioned in the center, in accordance with a scanning view angle, in an optical scanning lens constituted of three pieces of lenses. CONSTITUTION:The titled scanner is provided with a rotary polygon mirror 10 for deflecting and scanning a luminous flux from a light source 2, and a scanning lens 1 which has a function for correcting or decreasing the unevenness of a scanning line interval caused by the surface inclination of the rotary polygon mirror 10 and brings a luminous flux to an image formation at a position on the scanning surface being proportional to a deflection angle of the deflected luminous flux. In such a state, when each face of the optical scanning lens 1 constituted of three pieces of lenses is assumed as the first-the sixth faces 11-16 seen from the rotary polygon mirror side, the fourth face 14 goes to a face shape by which as the absolute value of a view angle increases, the radius of curvature in the surface inclination direction is varied, and the power decreases monotonously. In such a way, the image formation characteristic in the scanning direction is not deteriorated even if the view angle becomes larger. |
