REAR ATTACHMENT LENS

• Main Author: YONEZAWA KEN
• Format: Patent
• Language: English; Japanese
• Published: 14.12.2015
• Subjects: ACCESSORIES THEREFOR; APPARATUS OR ARRANGEMENTS EMPLOYING ANALOGOUS TECHNIQUES USINGWAVES OTHER THAN OPTICAL WAVES; APPARATUS OR ARRANGEMENTS FOR TAKING PHOTOGRAPHS OR FORPROJECTING OR VIEWING THEM; CINEMATOGRAPHY; ELECTROGRAPHY; HOLOGRAPHY; OPTICAL ELEMENTS, SYSTEMS, OR APPARATUS; OPTICS; PHOTOGRAPHY; PHYSICS

PROBLEM TO BE SOLVED: To provide a rear attachment lens that offers an extended focal length, good aberration correction, and high performance compatible with increasing pixel density.SOLUTION: A rear attachment lens is attached to a main lens on the image side thereof to achieve a focal length of the entire lens system after the attachment that is on the longer focal length side than a focal length of the main lens, and comprises a first lens group G1 and a second lens group G2 in order from the object side. The first lens group G1 comprises a negative lens and a positive lens in order from the object side. The second group G2 comprises one or more negative lenses and one or more positive lenses. The second lens group G2 has a positive lens on the most image side. An Abbe number d1 of the negative lens of the first lens group G1 for the d-ray and a partial dispersion ratio gF1 thereof between the g-ray and F-ray satisfy conditional expressions: (1) d1>62; and (2) 0.64< gF1+0.001625× d1<0.69. 【課題】長焦点距離化の作用、諸収差の良好な補正、高画素化に対応可能な高性能を実現したリアアタッチメントレンズを提供する。【解決手段】主レンズの像側に装着されて装着後のレンズ全系の焦点距離を主レンズの焦点距離よりも長焦点距離側へ変化させるものであり、物体側から順に、第１レンズ群Ｇ１、第２レンズ群Ｇ２からなる。第１レンズ群Ｇ１は、物体側から順に、負レンズ、正レンズからなる。第２レンズ群Ｇ２は、１枚以上の負レンズ、１枚以上の正レンズからなる。第２レンズ群Ｇ２の最も像側には正レンズが配置される。第１レンズ群Ｇ１の負レンズのｄ線基準のアッベ数、ｇ線とＦ線間の部分分散比を各々νｄ１、θｇＦ１としたとき、条件式（１）：νｄ１＞６２、条件式（２）：０．６４＜θｇＦ１＋０．００１６２５?νｄ１＜０．６９を満足する。【選択図】図３