| 摘要 |
PROBLEM TO BE SOLVED: To provide a rear attachment lens that is mounted to an image side of a main lens system, wherein fluctuation of many aberrations is small when the focal length of the whole system is changed to the longer side, especially the fluctuation of chromatic aberration is small, and that keeps high optical performance as the whole system.SOLUTION: The rear attachment lens is removably mounted to the image side of the main lens system, and changes the focal length to the longer side than the focal length of the main lens system. The rear attachment lens includes one or more diffractive optical elements, and one or more negative lenses GMn. It is required to appropriately set Abbe number and partial variance ratio differences νand Δθof material of the negative lenses GMn, the focal length fof the negative lenses GMn, the distance d from the lens surface of the attachment lens on the side closest to an object to the lens surface thereof on the side closest to the image, the distance tfrom the lens surface of the attachment lens on the side closest to the object to the lens surface of the negative lenses GMn on the object side, and the focal length f of the attachment lens. |
