Patent ID: 7864456

Claim:
An optical system comprising: a first optical element and a second optical element disposed on an enlargement side relative to a point P at which a light axis and a paraxial chief ray intersect, each of the first optical element and the second optical element comprising a solid material having a refractive light incident surface and a refractive light emergent surface, wherein the maximum height of a paraxial marginal ray from the light axis when the paraxial marginal ray passes through a lens surface on the enlargement side relative to the point P is greater than that on the reduction side relative to the point P, and wherein the following conditional expressions are satisfied: Î”Î¸gF1>0.0272, Î”Î¸ gF 2<âˆ’0.0278, f 1Ã— f 2<0, Ï†1Ã—Ï†2<0, and Lt/ft< 1.0 where Î”Î¸gF 1 and Î”Î¸gF 2 denote anomalous partial dispersion values of the first optical element and the second optical element for the Fraunhofer g-line and F-line, respectively, f 1 and f 2 denote focal lengths of the first optical element and the second optical element, respectively, when the light incident surfaces and the light emergent surfaces of the first optical element and the second optical element are in contact with air, Ï† 1 and Ï† 2 denote refractive powers of the first optical element and the second optical element, respectively, when the light incident and emergent surfaces of the first optical element and the second optical element are in contact with air, ft denotes a focal length of the entire optical system, and Lt denotes a total lens length of the optical system.