| 摘要 |
A super wide angle lens, having a viewing angle greater than 120 degrees, and an F-number of about 1.2 is disclosed. The lens is formed of a first lens group G1 of negative refractive power, a second lens group G2 of positive refractive power, and a third lens group G3 of positive refractive power. The lens is designed so that the lens elements used in the lens groups may be easily and economically manufactured. The first lens group has a first lens element L1 composed of a negative meniscus lens with its convex surface on the object side, and a second lens element L2 composed of a negative meniscus lens with its convex surface on the object side. The second lens group includes a third lens element L3, that is biconcave, cemented to a fourth lens element L4 that is biconvex. The third lens group has four lens elements: a fifth lens element L5 composed of a negative meniscus lens, with its convex surface on the object side; a sixth lens element L6 composed of a biconvex lens cemented to the fifth lens element; a seventh lens element L7 composed of a negative meniscus lens, with its convex surface on the object side; and an eighth lens element L8 composed of a biconvex lens cemented to the seventh lens element.
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