| 摘要 |
PROBLEM TO BE SOLVED: To obtain a finder optical system which is high in observation magnification, is capable of achieving observation of a large finder image, and is capable of securing a sufficiently long eye relief. SOLUTION: In the finder optical system in which a subject image formed by a photographic lens is made an erect image by an erect image-forming member so as to observe an object to be imaged through an eyepiece lens, the eyepiece lens includes, in order from the erect image forming member to an observation side: a first lens group having negative refractive power; a second lens group moved in an optical axis direction to adjust diopter and having positive refractive power; and a third lens group having one or more positive lenses and one or more negative lenses and having positive or negative refractive power as a whole. The optical system satisfies a conditional expression of -0.55<f3n/f<-0.30 when: a focal length of the entire system obtained when the eyepiece lens is set to -1 diopter is defined as f; and a synthetic focal length of the negative lenses of the third lens group is defined as f3n. COPYRIGHT: (C)2010,JPO&INPIT |
