| 摘要 |
PROBLEM TO BE SOLVED: To make the configuration of lens groups moved for back focus adjustment simpler and more compact and also minimize the fluctuation of lens performance involved in back focus adjustment by providing a zoom lens composed of four groups being positive, negative, negative and positive from the object side and forming the fourth group of a front group and a rear group which is composed of one positive lens. SOLUTION: This zoom lens consists of a positive first group I, a negative second group II that is moved at power variation to change power, a negative third group III that is moved at power variation to correct the fluctuation of an image surface involved in power variation, and a positive fourth group IV, wherein the fourth group IV consists of the front group IVa and the rear group IVb composed of one positive lens and adjusts the deviation of an image- formation position when the lens is mounted to a camera by moving the fourth latter group IVb.
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