PROBLEM TO BE SOLVED: To provide a high-performance lens system having long back focus which can be applied to the photographing lens of a high-performance electronic image equipment by adopting the constitution of a retrofocus type, arranging a combined lens in a 2nd lens group, and satisfying specified conditions. ;SOLUTION: This system is equipped with a 1st lens group G1 having negative refractive power, an aperture diaphragm and a 2nd lens group G2 having positive refractive power in order from an object side. The 1st lens group G1 has a negative meniscus lens and the 2nd lens group G2 is composed of a positive lens and the combined lens including the divergent bonding surface which is convex to the object side in order from the object side. Then, it is the lens system satisfying the conditions such as an expression: 0.5|f1|/f3.0 and an expression: 1.0bf/f5.0. In the expressions, f1 means the focal distance of the 1st lens group G1. (f) means the focal distance of an entire lens system. (bf) means the back focus.;COPYRIGHT: (C)1999,JPO
展开▼
机译：解决的问题：提供一种具有长后焦距的高性能镜头系统，通过采用后向对焦型的构造，将组合镜头布置在第二镜头中，该镜头系统可以应用于高性能电子图像设备的摄影镜头。组，并满足指定条件。 ;解决方案：该系统从物体侧开始依次配备有具有负屈光力的第一透镜组G1，光圈和具有正屈光力的第二透镜组G2。第一透镜组G1具有负弯月形透镜，第二透镜组G2由正透镜和组合透镜构成，该组合透镜包括从物侧开始向物侧凸出的发散接合面。然后，是满足以下条件的透镜系统：表达式：0.5 ＜f1 / f ＜3.0;表达式：1.0 ＜bf / f ＜5.0。在这些表达式中，f1表示第一透镜组G1的焦距。 （f）表示整个镜头系统的焦距。 （bf）表示后焦点。;版权：（C）1999，JPO
展开▼
