IMAGE FORMATION OPTICAL SYSTEM AND IMAGING DEVICE USING THE SAME

摘要

PROBLEM TO BE SOLVED: To provide an image formation optical system in which an entire length remains stationary when focused with a size reduced and an amount of peripheral light secured, while securing a wide angle of view.SOLUTION: An image formation optical system comprises: a front side lens group LF that is composed of a negative first sub lens group L1 and a positive second lens group L2; and a positive rear side lens group LR that is composed of a third sub lens group L3 and a fourth sub lens group having a positive refractive index, and satisfies following conditional expressions (1), (2) and (3), -140%≤DT≤-7% (1), -2.2≤R_L3f/f≤-0.25 (2) and 0.8≤R_L1f/f≤5.5 (3), where DT=(IHω-f×tanω)/(f×tanω)×100%,ωdenotes a maximum half angle of view of the image formation optical system, IHωdenotes a distance from an intersection where a principal light beam at the maximum half angle of viewωintersects an imaging plane, f denotes a focal length of an entire system, R_L3f denotes a paraxial radius of curvature of a lens surface on the most object side of the third sub lens group, R_L1f denotes a paraxial radius of curvature of a lens surface on the most object side of the first sub lens group, and fLF denotes a focal length of the front side lens group.