REAL-IMAGE TYPE VARIABLE POWER VIEWFINDER

摘要

PROBLEM TO BE SOLVED: To make it possible to vary high power with simple constitution and to improve the productivity while having high-performance aberrational characteristics by fixing a 1st and a 4th lens group and moving a 2nd and a 3rd lens group in the optical axis direction when the power is varied from a wide-angle end to a telephoto end. ;SOLUTION: This viewfinder is composed of an objective lens group I, an image inversion optical system II, and an ocular group III. The objective group I is composed of a 1st lens group 1 with positive refracting power, a 2nd lens group 2 with negative refracting power, a 3rd lens group with positive refracting power, and a 4th lens group 4 with positive refracting power. The 1st lens group 1 and 4th lens group 4 of the objective group I are fixed and the 2nd lens group 2 and 3rd lens group 3 are moved in the optical axis direction to vary the power. Further, 0.6fw/f₃1.0 and 18fr33 are satisfied. Here, f₃ is the focal length of the 3rd lens group, fw is the focal length of the objective group at the wide-angle end, and fr is the focal length of the objective group at the telephoto end.;COPYRIGHT: (C)1997,JPO