Patent ID: 7149019
Filing Date: 2006-12-12
Classification: G02B

Abstract:
1. An optical scanning system, comprising: light source means; deflecting means configured to deflect a light beam emitted from said light source means in a main-scan direction; and an imaging optical system configured to image the light beam, deflected by said deflecting means, on a scan surface to be scanned; wherein, in a sub-scan sectional plane, said imaging optical system is configured to place a deflecting surface of said deflecting means and the scan surface in a conjugate relationship with each other; wherein a curvature, in the sub-scan sectional plane, of both of a light entrance surface and a light exit surface of at least one imaging optical element that is a constituent component of said imaging optical system changes, inside an effective region, continuously from an optical axis of said imaging optical system toward a peripheral portion of the same, and wherein a sign of each of the curvatures of the light entrance surface and the light exit surface of said imaging optical element with respect to the sub-scan sectional plane is reversed within the effective region; wherein, when a curvature radius of the light entrance surface of said imaging optical element at the optical axis thereof, with respect to the sub-scan sectional plane, is denoted by rl rl |rl are satisfied; and wherein, when a shape x of the light entrance surface or the light exit surface of said imaging optical element in a main-scan sectional plane is expressed in terms of a function x=g(y) of an arbitrary coordinate y in the main-scan direction inside an effective scan region of said imaging optical element and when an absolute value of a difference between a second differential quantity of x at the coordinate y and a second differential quantity of x at a coordinate y+0.01 is denoted by |δd |δd