| 摘要 |
PROBLEM TO BE SOLVED: To provide a wide-angle lens made small in size and light in weight, manufactured at low cost and having a long exit pupil. SOLUTION: The lens optical system 100 of the wide-angle lens is provided with a 1st group lens 10 having negative power and a 2nd group lens 20 having positive power arranged in order from an object side. The 2nd group lens 20 is equipped with a front group lens 30 arranged on the object side and a rear group lens 40 arranged on an opposite side while putting a diaphragm 5 in between, and at least three surfaces of the lens surfaces of the lens groups constituting an entire lens system are made aspherical. When it is assumed that the focal distance of the 1st group lens 10 is F1, the focal distance of the 2nd group lens 20 is F2, the focal distance of the front group lens 30 is (fm), the focal distance of the rear group lens 40 is fR, the focal distance of the entire lens system is Fo, and the Abbe number of the front group lens 30 isνdm, they satisfy following conditional expressions (1), (2) and (3). (1) 0.5<fm/fR<3.0, (2)νdm<45 (3) 0.5<|F1/F2|<3.0.
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