| 摘要 |
PURPOSE:To make a zoom lens compact on the whole by providing operation for image plane position compensation by the variable power of a front lens group and incorporating the focus lens of a master lens group in a control system which performs focusing operation with a video signal. CONSTITUTION:A zoom lens system consists of the front lens group 1 which has positive refracting power and moves in the optical axis direction to hold an image plane position varying the variable power invariably constant, a variator lens group 2 which has a negative refractive index and moves in the optical axis direction to perform a variable power operation for varying the focal length of the whole zoom lens system, and the master lens group 3 which has positive refracting power and moves in the optical axis direction to perform the focusing operation. Then the focus lens 3b of the master lens group 3 as a focusing lens is incorporated in the automatic focusing control mechanism system which performs automatic focusing operation with the video signal. Consequently, there are only two lens groups except lens groups regarding the focusing operation and the zoom lens can be made compact on the whole. |
