OPTICAL SYSTEM AND IMAGING APPARATUS HAVING THE SAME

• Main Author: GYODA YUICHI
• Format: Patent
• Language: English; Japanese
• Published: 24.11.2017
• Subjects: OPTICAL ELEMENTS, SYSTEMS, OR APPARATUS; OPTICS; PHYSICS

PROBLEM TO BE SOLVED: To provide an optical system which facilitates quick focusing, has high optical performance over the whole object distance and easily maintains high optical performance upon correcting image blur.SOLUTION: The optical system includes, successively disposed from an object side to an image side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, and a third lens group having a positive refractive power. Upon focusing from an infinite distance to a close range, the second lens group moves toward an image and an interval between adjoining lens groups varies. The first lens group is composed of, successively disposed from the object side to the image side, a 1A group having a negative refractive power and immobile upon correcting image blur, a 1B group having a positive refractive power which moves upon correcting image blur, and a 1C group immobile upon correcting image blur. A distance DL from a lens surface closest to the object of the first lens group to an image plane when the system is focused to an infinite distance, and a distance DB from a lens surface closest to the object of the 1B group to the image plane when the system is focused to the infinite distance are each appropriately set.SELECTED DRAWING: Figure 1 【課題】 迅速なフォーカスが容易で、全物体距離にわたり高い光学性能を有し、しかも像ぶれ補正に際しても高い光学性能を維持することが容易な光学系を得ること。【解決手段】 物体側から像側へ順に配置された、正の屈折力の第１レンズ群、負の屈折力の第２レンズ群、正の屈折力の第３レンズ群より構成され、無限遠から至近距離へのフォーカシングに際して、第２レンズ群が像側へ移動し、隣り合うレンズ群の間隔が変化する光学系であって、第１レンズ群は、物体側から像側へ順に配置された、像ぶれ補正に際して不動である負の屈折力の１Ａ群と、像ぶれ補正に際して移動する正の屈折力の１Ｂ群と、像ぶれ補正に際して不動の１Ｃ群より構成され、無限遠に合焦しているときにおける第１レンズ群の最も物体側のレンズ面から像面までの距離をＤＬ、無限遠に合焦しているときにおける１Ｂ群の最も物体側のレンズ面から像面までの距離をＤＢを各々適切に設定する。【選択図】 図１