| 摘要 |
A rear attachment lens changes a focal-length of an entire lens-system, in which the rear attachment lens has been attached to a main-lens, to a longer focal-length-side than a focal-length of the main-lens by being attached to an image-side of the main-lens. The rear attachment lens consists essentially of a first-lens-group and a second-lens-group in this order from an object-side. The first-lens-group consists essentially of a negative lens and a positive lens in this order from the object-side. The second-lens-group consists essentially of at least one negative lens and at least one positive lens, and a lens closest to an image-side in the second lens-group is a positive lens. When an Abbe number for d-line and a partial dispersion ratio between g-line and F-line of the negative lens in the first-lens-group are νd1 and θgF1, respectively, conditional expression (1): νd1>62 and conditional expression (2): 0.64<θgF1+0.001625 ×νd1<0.69 are satisfied. |
| 主权项 |
1. A rear attachment lens that is attachable to a main lens, which is an imaging optical system, and changes a focal length of an entire lens system, in which the rear attachment lens has been attached to the main lens, to a longer focal length side than a focal length of the main lens by being attached to an image side of the main lens,
the rear attachment lens consisting of: a first lens group; and a second lens group in this order from an object side, wherein the first lens group consists of a negative lens and a positive lens in this order from the object side, and wherein the second lens group consists of at least one negative lens and at least one positive lens, and a lens closest to an image side in the second lens group is a positive lens, and wherein when an Abbe number for d-line and a partial dispersion ratio between g-line and F-line of the negative lens in the first lens group are νd1 and θgF1, respectively, the following conditional expressions (1) and (2) are satisfied:
νd1>62 (1); and0.64<θgF1+0.001625×νd1<0.69 (2). |
