| 摘要 |
PROBLEM TO BE SOLVED: To obtain an objective lens which is bright, is small in size over the entire part of a lens system and is adequate for telescopes, binoculars, etc. SOLUTION: The first lens group of the objective lens comprising, successively from an object side, the first lens group having positive refracting power and a second lens group having negative refracting power consists of a single lens having positive refracting power and the second lens group consists of a positive lens and a negative lens. Fall, defined as the focal length of the entire system of the objective lens, f1 as the focal length of the first lens group, f2 as focal length of the second lens group and D12 as the air spacing between the first lens group and the second lens group are respectively adequately set.
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