| 摘要 |
The invention provides a high-performance objective lens that is capable of implementing focusing relative to an object point distance change with no or little angle-of-view change, and is well compatible with a high-pixel type imaging device. The objective optical system comprises, in order from an object side thereof, a first group of negative power, a second group of positive power, an aperture stop, and a third group of positive power. Only the second group moves thereby implementing focusing relative to an object point distance change, with satisfaction of the following conditions (1)-1, (1)-2 and (8):ωf>60 (1)-1ωn>60 (1)-2−1.2<f1/ff<−0.6 (8) whereωf is a maximum half angle of view (°) upon viewing at a far distance object point,ωn is a maximum half angle of view (°) upon close-up viewing, f1 is a focal length of the first lens group, and ff is a focal length of the whole system upon viewing at a far distance. See FIG. 1.
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