Imaging Optical System, Imaging Optical Device, and Digital Apparatus

摘要

An imaging optical system includes first to third lens groups, and performs focusing by moving the second lens group, to satisfy the following conditional expressions:;0.8<1Gr—Fl/FL<1.2,;0.6<|2Gr—Fl/FL|<2.5,;0.6<3Gr—Fl/FL<1.8;0.8<1Gr—R—nop/1Gr—Thi<1.1, and;−0.6<2Gr—R—nop/2Gr—Thi<1.6;where FL, 1Gr_Fl, 2Gr_Fl, and 3Gr_Fl represent focal lengths of the entire system, and the first to third lens groups, respectively, 1Gr_R_nop represents a distance from the outermost surface of the first lens group on the object side to a rear principal point of the first lens group, 1Gr_Thi represents a total length of the first lens group, 2Gr_R_nop represents a distance from the outermost surface of the second lens group on the object side to a rear principal point of the second lens group, and 2Gr_Thi represents a total length of the second lens group.

主权项

1. An imaging optical system comprising
a first lens group of positive lenses, a second lens group of negative lenses, and a third lens group of positive lenses in order from an object side, wherein focusing on a nearby object is performed by moving the entire second lens group along an optical axis toward an image side, and the following conditional expressions (1) to (5) are satisfied:
0.8<1Gr—Fl/FL<1.2  (1),0.6<|2Gr—Fl/FL|<2.5  (2),0.6<3Gr—Fl/FL<1.8  (3),0.8<1Gr—R—nop/1Gr—Thi<1.1  (4), and−0.6<2Gr—R—nop/2Gr—Thi<1.6  (5),where
FL represents a focal length of the entire system, 1Gr_Fl represents a focal length of the first lens group, 2Gr_Fl represents a focal length of the second lens group, 3Gr_Fl represents a focal length of the third lens group, 1Gr_R_nop represents a distance from the outermost surface of the first lens group on the object side to a rear principal point of the first lens group, 1Gr_Thi represents a total length of the first lens group, 2Gr_R_nop represents a distance from the outermost surface of the second lens group on the object side to a rear principal point of the second lens group, and 2Gr_Thi represents a total length of the second lens group.