LARGE-APERTURE WIDE-ANGLE ZOOM LENS

PROBLEM TO BE SOLVED: To provide a large-aperture wide-angle zoom lens which has a lighter focusing group, does not require a correction cam to prevent defocusing when zooming at a finite distance, exhibits less image height variation while wobbling, is best suited for an inner focus system, and features a bright F-number of approximately 2.8 over an entire zoom range, a focal length of approximately 24 mm at the wide-angle end, and good optical performance over the entire zoom range.SOLUTION: A large-aperture wide-angle zoom lens consists of a first lens group G1 having negative refractive power, second lens group G2 having positive refractive power, third lens group G3 having positive refractive power, aperture stop, fourth lens group G4 having negative refractive power, fifth lens group G5 having positive refractive power, and sixth lens group G6 having negative refractive power arrange in order from the object side; is configured such that the second lens group G2 moves toward an image plane when shifting focus from an infinite object distance to a short distance; and satisfies predetermined conditions.SELECTED DRAWING: Figure 1 【課題】フォーカスレンズ群が軽量化され、有限距離における変倍時のピントずれを防ぐために補正カムを不要とし、ウオブリング時の像高変化率が小さく、インナーフォーカス方式に最適で、ズーム全域でＦナンバーが２．８程度と明るく、広角端の焦点距離が２４ｍｍ程度を有し、全ズーム範囲において良好な光学性能を有する大口径広角ズームレンズを提供する。【解決手段】物体側より順に負の屈折力の第１レンズ群Ｇ１、正の屈折力の第２レンズ群Ｇ２、正の屈折力の第３レンズ群Ｇ３、開口絞り、負の屈折力の第４レンズ群Ｇ４、正の屈折力の第５レンズ群Ｇ５、負の屈折力の第６レンズ群Ｇ６で構成され、物体距離無限遠から近距離へフォーカシングする際、前記第２レンズ群Ｇ２が像面方向へ移動し、所定の条件を満足することを特徴とする大口径広角ズームレンズ。【選択図】図１