| 摘要 |
PURPOSE:To obtain a compact lens system having a large aperture ratio of about F1.2 and a zooming ratio of about 6 times by constituting the titled lens system of specific five lens groups so as to be constituted of 13 lenses as a whole and satisfying specific conditions. CONSTITUTION:The 1st positive lens group I to be fixed at the time of zooming, the 2nd negative lens group II to be moved to execute power modification at the time of zooming, the 3rd negative lens groups III interlocking with the 2nd group at the time of zooming to keep its image plane at a fixed position, the 4th positive lens group IV to be fixed at the time of zooming to refract the light flux dispersed from the 3rd group III like a focal or slightly converged state, a diaphragm S, and the 5th positive lens group V arranged on a position separated from the diaphragms S and fixed at the time of zooming to form an image are arranged successively from the object side to constitute the zoom lens. In addition, the zoom lens system should satisfy the conditions of the formulas (1) and (2). Provided that n10 is the refractive index of the 4th negative meniscus lens, r10 is the radius of curvature of the object side surface of the 4th lens, fw is the composite focal distance of the whole system at a wide end, f12 is focal distance of the 5th negative meniscus lens, and fv is the composite focal distance of the 5th group. |
