| 摘要 |
PURPOSE:To obtain a photographic lens with long back focus which is suitable to an SV camera by composing the photographic lens of five lens elements in five groups and specifying the respective lens elements. CONSTITUTION:The lens system consists of the 1st meniscus lens which has its convex lens at an object side and negative refracting force, the 2nd biconvex lens, the 3rd biconcave lens, the 4th lens having the convex surface on the image side, and the 5th biconvex lens. Then, inequalities hold, where (f) is the focal length of the whole system, fi is the focal length of the (i)th lens elements, and f2-f5 are composite focal lengths of the 2nd - the 5th lenses.
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