OPTICAL SYSTEM

• Main Author: SHIODA RYO
• Format: Patent
• Language: English; Japanese
• Published: 21.01.2016
• Subjects: OPTICAL ELEMENTS, SYSTEMS, OR APPARATUS; OPTICS; PHYSICS

PROBLEM TO BE SOLVED: To provide a large-aperture optical system that is capable of providing good image quality over an entire screen by correcting aberrations well and is compact enough to be coupled to average camera bodies such as those of SLR cameras.SOLUTION: An optical system comprises a first lens group having positive or negative refractive power, and a second lens group having positive refractive power in order from the object side to the image side, where the first lens group has a meniscus lens L1 having a convex surface on the object side and negative refractive power, one or more lenses having positive refractive power, and one or more lenses having negative refractive power, and the second lens group comprises a front second group having positive refractive power and a rear second group having positive refractive power in order from the object side to the image side. When shifting focus from an object at infinity to an object at a short distance, the second lens group moves toward the object side. The optical system satisfies predefined conditional expressions. 【課題】諸収差を良好に補正することで画面全域で良好な画質を得る事が可能であり、一眼レフカメラ等の一般的なカメラボディに連結できる程度に小型化を図った大口径の光学系を提供する。【解決手段】物体側から像面側に順に、正または負の屈折力を持つ第１レンズ群と、正の屈折力を持つ第２レンズ群とから成り、前記第１レンズ群が、物体側に凸面を向けた負の屈折力を持つメニスカスレンズＬ１を有し、さらに正の屈折力を持つレンズと負の屈折力を持つレンズをそれぞれ１枚以上有し、前記第２レンズ群が、物体側から像面側に順に、正の屈折力を持つ第２レンズ群前群と正の屈折力を持つ第２レンズ群後群とから成り、無限遠物体から近距離物体へのフォーカシングに際して、前記第２レンズ群が物体側へ移動し、所定の条件式を満足させる。【選択図】 図１