| 摘要 |
A fisheye lens with a field angle of at least one hundred sixty degrees is formed of two lens groups, arranged in order from the object side, as follows: a first lens group having negative refractive power and a second lens group having positive refractive power. The first lens group includes, arranged in order from the object side, two lens elements, each having negative refractive power and a meniscus shape with the convex surface on the object side, a lens element having negative refractive power with a concave surface on the image side, and two lens elements of opposite refractive powers. The second lens group includes, arranged in order from the object side, two lens elements of opposite refractive powers, a stop, and two lens elements of opposite refractive powers. The fisheye lens preferably satisfies specified conditions related to spacings of lens surfaces and to distortion characteristics of the fisheye lens.
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