| 主权项 |
1. A projection optical system comprising:
a first lens unit that moves in a direction of an optical axis in adjusting an amount of field curvature; and a second lens unit located closer to a reduction side than the first lens unit, wherein the first lens unit includes an aspherical lens, when a paraxial radius of curvature of a surface of the aspherical lens at an enlargement side is denoted by R1, an effective diameter is denoted by φ1, a sagittal amount in a position at a height of φ1/2 from the optical axis on the surface at the enlargement side is denoted by SAG1, a paraxial radius of curvature of the surface of the aspherical lens at a reduction side is denoted by R2, an effective diameter is denoted by φ2, and a sagittal amount in a position at a height of φ2/2 from the optical axis on the surface at the reduction side is denoted by SAG2, the following conditions are satisfied:
SR1={(φ1/2)̂2+SAG1̂2}/(2×SAG1)SR2={(φ2/2)̂2+SAG2̂2}/(2×SAG2)1.0<|R1/SR1|/|R2/SR2|≦5.0, and when a focal length of the entire system of the projection optical system is denoted by ftot and a paraxial focal length of the aspherical lens is denoted by fg1, the following condition is satisfied:
3<|fg1/ftot|≦14.50. |
