| 摘要 |
PURPOSE:To make the titled lens large in variable power rate and excellent in performance by varying an interval between the I lens group the and II lens group, and also moving the whole, and keeping a distance between an object surface and an image forming surface. CONSTITUTION:The I lens group consists of the first positive lens, the second negative lens, the third negative lens and the fourth positive lens, and the IIlens group consists of the fifth lens being a positive meniscus lens whose convex surface faces to an image side, and the sixth lens being a negative meniscus lens whose convex surface faces to an image side. Also, they are constituted so as to satisfy each condition shown in the expression. In this regard, Fmax: a focal distance 1,00 time of the whole system, FI: a focal distance of the I lens group, FII: a focal distance of the II lens group, fi: a focal distance of the i-th lens in order from the object side, and Ni: a refractive index (nd) of the i-th lens in order from the object side. The power of the I lens group is shown by a condition 1, the power distribution is limited by a condition 2 or 3; and conditions 4, 5 are used as a nitric material condition. |
