Patent ID: 7626771

Claim:
An optical system in which a maximum value of a height from an optical axis of a paraxial marginal ray closer to an expanded side than a point P, P denoting a point of intersection between an optical axis and a paraxial chief ray, and in a lens surface of the expanded side is larger than a maximum value of a height from an optical axis closer to a reduced side than the point P in which the paraxial marginal ray passes through the lens surface, the optical system comprising: closer to the reduced side than the point P, a lens unit Lr including at least one refractive optical element Gn of a negative refractive power in which light entrance and exit surfaces are both refractive surfaces made of solid-state material, wherein when an Abbe number of a material of the refractive optical element Gn is νd (Gn), a partial dispersion ratio regarding g and F-lines is θgF (Gn), and a focal length of the refractive optical element Gn is FGn, a focal length of the lens unit Lr is Fr, the following conditions are satisfied: −2.100×10 −3 ·νd ( Gn )+0.693<θ gF ( Gn ) 0.55<θ gF ( Gn )<0.90 0.02<| FGn/Fr|< 10.00.