IMAGE CAPTURING OPTICAL SYSTEM, IMAGE CAPTURING OPTICAL DEVICE, AND DIGITAL EQUIPMENT

• Main Authors: YAMAMOTO YASUSHI, HIROSE TAKAKAZU, IMAJIMA RYOSUKE, TANAHASHI DAISUKE, MURATANI MAMI
• Format: Patent
• Language: English; Japanese
• Published: 22.10.2020
• Subjects: OPTICAL ELEMENTS, SYSTEMS, OR APPARATUS; OPTICS; PHYSICS

To provide an image capturing optical system which features both a bright F-number and a lighter focusing group, and yet is well corrected for aberrations from an infinity end to a proximity end and capable of providing uniform image quality over an entire image, and to provide an image capturing optical device and digital equipment having the same.SOLUTION: An image capturing optical system LN provided herein consists of first through fourth lens groups Gr1-Gr4 having positive, negative, positive and negative power, respectively, and is configured such that the second lens group Gr2 moves toward the image side and the third lens group Gr3 moves toward the object side when shifting focus from infinity to a nearby object. The second lens group Gr2 consists of a cemented lens of a positive lens L21 and a negative lens L22 in order from the object side, and the third lens group Gr3 consists of a positive lens L31. The second and third lens groups satisfy conditions expressed as: nd(2GrP)-nd(3GrP)>0.2 and νd(3GrP)-νd(2GrP)>40, where nd(2GrP) and nd(3GrP) respectively represent refractive indices of the positive lenses L21, L31 for the d-ray, and νd(2GrP) and νd(3GrP) respectively represents Abbe numbers of the positive lenses L21, L31 for the d-ray.SELECTED DRAWING: Figure 1 【課題】明るいＦ値とフォーカス群の軽量化とを両立しながら、無限端から至近端に至るまで収差が良好に補正され、画像全体で均一な画質を得ることが可能な撮像光学系，それを備えた撮像光学装置及びデジタル機器を提供する。【解決手段】撮像光学系ＬＮは、正負正負の第１〜第４レンズ群Ｇｒ１〜Ｇｒ４からなり、無限遠から至近物体へのフォーカシングにおいて、第２レンズ群Ｇｒ２が像側に移動し、第３レンズ群Ｇｒ３が物体側に移動する。第２レンズ群Ｇｒ２が物体側から順に正レンズＬ２１と負レンズＬ２２との接合レンズからなり、第３レンズ群Ｇｒ３が正レンズＬ３１からなり、条件式：ｎｄ（２ＧｒＰ）−ｎｄ（３ＧｒＰ）＞０．２，νｄ（３ＧｒＰ）−νｄ（２ＧｒＰ）＞４０を満足する。ただし、ｎｄ（２ＧｒＰ），ｎｄ（３ＧｒＰ）：正レンズＬ２１，Ｌ３１のｄ線に関する屈折率、νｄ（２ＧｒＰ），νｄ（３ＧｒＰ）：正レンズＬ２１，Ｌ３１のｄ線に関するアッベ数である。【選択図】図１