| 摘要 |
PROBLEM TO BE SOLVED: To provide an image forming optical system that can satisfactorily correct aberrations from a long range to a close range and can form high-definition images.SOLUTION: The present image forming optical system is an image forming optical system having, in order from an enlargement conjugate side to a reduction conjugate side, a first lens group having a negative refractive power that does not move for zooming and a plurality of lens groups that move in zooming, where the first lens group comprises, in order from the enlargement conjugate side to the reduction conjugate side, three lens groups: a first a lens group having a negative refractive power and fixed during focusing, a first b lens group having a negative refractive power, and a first c lens group having a positive refractive power; the first b lens group and first c lens group move from the enlargement conjugate side to the reduction conjugate side during focusing from infinity to a close range, while reducing the interval between the first b lens group and first c lens group.SELECTED DRAWING: Figure 1 |
