OPTICAL SYSTEM AND IMAGING APPARATUS HAVING THE SAME

• Main Authors: NAKADA TAKEHARU, HATADA TAKAHIRO
• Format: Patent
• Language: English; Japanese
• Published: 20.01.2023
• Subjects: OPTICAL ELEMENTS, SYSTEMS, OR APPARATUS; OPTICS; PHYSICS

To provide an optical system that can reduce the weight of a focus group, and a photographing device having the same.SOLUTION: An optical system has a first lens group having a positive refractive power, an aperture diaphragm, a second lens group having a negative refractive power, and a third lens group having a positive refractive power, which are arranged in order from an object side to an image side. In the optical system, the distance between the adjacent lens groups changes in focusing. In focusing from an infinite-distance object to a closest-distance object, the second lens group moves to the image side. The first lens group includes a positive lens arranged on the most object side and two or more negative lenses. The second lens group consists of one negative lens. The distance on an optical axis from a lens surface on the most object side of the first lens group to a lens surface on the most image side of the first lens group, the distance on the optical axis from the lens surface on the most object side of the first lens group to an image surface, the focal distance of the optical system, and back focus of the optical system during focusing on the infinite-distance object are each appropriately set.SELECTED DRAWING: Figure 1 【課題】合焦群の軽量化を実現することができる光学系及びそれを有する撮影装置を提供すること。【解決手段】光学系は、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、開口絞り、負の屈折力の第２レンズ群、正の屈折力の第３レンズ群を有し、フォーカシングに際して隣り合うレンズ群の間隔が変化する光学系であって、無限遠物体から最至近物体へのフォーカシングに際して、第２レンズ群は像側へ移動し、第１レンズ群は、最も物体側に配置された正レンズと、２枚以上の負レンズとを含み、第２レンズ群は、１枚の負レンズからなり、第１レンズ群の最も物体側のレンズ面から第１レンズ群の最も像側のレンズ面までの光軸上での距離、第１レンズ群の最も物体側のレンズ面から像面までの光軸上での距離、光学系の焦点距離、無限遠物体合焦時の光学系のバックフォーカスを各々適切に設定すること。【選択図】図１