| 摘要 |
PROBLEM TO BE SOLVED: To provide a telecentric objective lens in which a field angle can be widened, and full lens length can be shortened by adopting a retro-focus type. SOLUTION: This objective lens is provided with a first group 103 consisting of a meniscus-shaped negative first lens whose concave recessed face faces an image face side, a second group 104 consisting of a positive second lens, a third group 105 having a negative refractive power as a whole and consisting of a joint lens formed by joining a negative third lens whose concave face faces an objective side and a positive fourth lens whose convex face faces the image face side, and a fourth group 106 consisting of a positive fifth lens. In this case, when the focal distance of the (i)th group is fi, the synthetic focal distance of the first group 103 and the second group 104 is f12, and the focal distance of the whole system is (f), a condition formula that 0.7<|f1|/f<3.0, 0.7<f4/f<3.0, and 0.8<f12/f<2.5 is satisfied.
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