| 摘要 |
PURPOSE:To maintain an excellent image formation performance by moving relatively plural lens groups for constituting an extender optical system, along the optical axis, in accordance with a signal from a photographing state detecting means. CONSTITUTION:When an extender optical system is moved in order to correct an aberration of a zoom lens, a movement of an image point position is generated, therefore, in order to keep an image surface position constant by correcting a variation of the aberration, it is necessary to make at least two or more lens groups movable. When correcting a variation of an aberration generated in the zoom lens body by a movement of the lens groups for constituting the extender optical system, in order that the movement of the image point position is not generated, when a moving extent of the first lens group G1, and a moving extent of the second lens group G2 are denoted as (x) and (y), respectively, it is necessary to move the first lens group G1 and the second lens group G2 so as to satisfy the expression. In this way, it becomes possible to maintain an excellent image formation performance and to attain automatically a stable performance at all times in every photographing state of the zoom lens. |
