| 摘要 |
PURPOSE:To give a wide angle to a light scanning lens to make an optical scanner compact and low-cost by using a single lens as a second image forming optical system which scans a surface to be scanned at an approximately uniform velocity and setting the focal length in the main scanning direction, etc., to meet specific conditions. CONSTITUTION:A second image forming optical system 6 which scans a surface 7 to be scanned at an approximately uniform velocity is a single lens and has a cylinder face having a negative refracting power in the subscanning scanning direction on the side of a deflecting device and has a toric face having a positive refracting power different in the main scanning direction and the subscanning direction on the side of the surface 7 to be scanned. Conditions of inequalities I and II are satisfied where (f), theta, (d), (n), D, and S are the focal length in the main scanning direction, a maximum effective deflection angle in the main scanning direction, the thickness of the center, the refractive index, the distance from the start point of deflection to the cylinder face, and the distance from a front principal point in the main scanning direction to the convergence point of a converging optical system in the main scanning direction respectively. Thus, an ultrawide angle is attained and the variance of scanning pitch in the subscanning direction due to surface inclination is eliminated. |
