Patent ID: 6464363
Filing Date: 2002-10-15
Classification: G02B,G02C,G02F,G03B

Abstract:
A decentered optical system comprising, at least, a front optical surface and a variable optical surface, which are disposed along a direction in which a light beam travels;said front optical surface being a reflecting surface reflecting the light beam obliquely incident thereon in an oblique direction; said variable optical surface being formed by an active reflecting optical element that reflects the light beam obliquely incident thereon in an oblique direction and changes a configuration of a reflecting surface thereof to change a focal length; wherein a driving member drives said active reflecting optical element so that the configuration of the reflecting surface thereof is changed; wherein, when driven by said driving member, said active reflecting optical element changes the configuration of the reflecting surface into a rotationally asymmetric curved surface configuration that corrects rotationally asymmetric decentration aberrations produced by the light beam obliquely incident thereon; and wherein when an optical path length of an axial principal ray from said front optical surface to the variable optical surface of said active reflecting optical element is denoted by &Dgr;Lf, the following condition (2) is satisfied: 0.001f<1000(mm)â€ƒâ€ƒ(2).