Patent ID: 7643228
Filing Date: 2010-01-05
Classification: G02B

Abstract:
1. An optical system comprising: a first optical element and a second optical element on at least one of an enlargement side and a reduction 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 following conditional expressions are satisfied: where ΔθgF 1 and ΔθgF 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, and 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, and wherein the first optical element and the second optical element are disposed in the same lens group.