OPTICAL SYSTEM

• Main Author: SHIODA RYO
• Format: Patent
• Language: English; Japanese
• Published: 22.06.2015
• Subjects: OPTICAL ELEMENTS, SYSTEMS, OR APPARATUS; OPTICS; PHYSICS

PROBLEM TO BE SOLVED: To provide an optical system of a large diameter that has various aberrations excellently corrected to obtain an excellent image quality over an entire screen, attains reduction in size of a product, and is suitable for an interchangeable lens.SOLUTION: An optical system comprises, in order from an object side, a first lens group G1, and a second lens group G2 having positive refractive power. The first lens group comprises, in order from the object side, a first lens group front group G1A having negative refractive power and a first lens group rear group G1B having positive refractive power which are spaced at the longest air distance on an optical axis in the first lens group G1. A surface on a most image surface I side of the first lens group front group G1A is configured to have a concave surface directed to the image surface I side, and a surface on the most object side of the first lens group rear group G1B is configured to have the concave surface directed to the objet side, and a surface on the most image surface I side of the first lens group rear group G1B is configured to have a convex surface directed to the image surface I side. The second lens group G2 comprises, in order from the object side, a second lens group front group G2A having positive refractive power, and a second lens group rear group G2B having the positive refractive power, and upon focusing an object from an infinite distance to a closest distance, the second lens group G2 is configured to be moved along the optical axis from the image surface I side to the object side. 【課題】諸収差を良好に補正し画面全域で良好な画質を得、製品の小型化を図り、交換レンズに適した大口径の光学系を提供する。【解決手段】物体側から順に、第１レンズ群Ｇ１と、正屈折力の第２レンズ群Ｇ２とからなり、第１レンズ群Ｇ１は、物体側から順に、第１レンズ群Ｇ１の中で最も長い光軸上の空気間隔を隔てて、負屈折力の第１レンズ群前群Ｇ１Ａと正屈折力の１レンズ群後群Ｇ１Ｂとからなり、第１レンズ群前群Ｇ１Ａの最も像面Ｉ側の面は、像面Ｉ側に凹面を向け、第１レンズ群後群Ｇ１Ｂの最も物体側の面は、物体側に凹面を向け、第１レンズ群後群Ｇ１Ｂの最も像面Ｉ側の面は、像面Ｉ側に凸面を向け、第２レンズ群Ｇ２は、物体側から順に、正屈折力の第２レンズ群前群Ｇ２Ａと正屈折力の第２レンズ群後群Ｇ２Ｂとからなり、無限遠物体から近距離物体へのフォーカシング時に、第２レンズ群Ｇ２を光軸に沿って像面Ｉ側から物体側へ移動すること。【選択図】図１