| 摘要 |
PROBLEM TO BE SOLVED: To excellently take both of a close-up photograph and infinity photograph even when adding a lens shift function to an ultra wide-angle lens system, and to allow a high-performance multi-function of an ultra wide-angle lens device to be attained.SOLUTION: A wide-angle lens device includes, in a front lens group Gf located on a subject side Fs relative to an aperture diaphragm part 2, more specifically, in a second lens group G2 on an image-formation side Dr: a first lens unit Lj1 using a cemented lens positioned first from a subject side Df; a second lens unit Lj2 using the cemented lens positioned second from the subject side Df; and a third lens group Lj3 using the cemented lens positioned third from the subject side Df. Let a focal length of an entire optics be F0, a back focus of the entire optics be BF, a focal length of the first lens unit Lj1 be FC1, a focal length of the second lens unit Lj2 be FC2, and a focal length of the third lens unit Lj3 be FC3, the wide-angle lens device is configured to satisfy an optical condition of (BF/F0)>2.9 and FC1<FC2<FC3. |
