| 摘要 |
PURPOSE:To obtain a wide angle lens compensated at its various aberrations by satisfying an optical system constiting of nine meniscus lenses arranged in the positive, negative, negative, positive, positive, positive, positive, negative, positive, and positive order successively from the object side with prescribed conditions. CONSTITUTION:The 1st lens is opposed at its convex surface to the object side, the 2nd and 3rd lenses are opposed at their convex surfaces to the object side, the 4th, 5th and 6th lenses are opposed at their small radius curvatures surfaces to the image side, the 7th lens has both concave surfaces and the 8th and 9th lenses are opposed at their small radius corvature surfaces to the image side, A retrofocus type lens system consisting of 8 groups/9 lenses as a whole is constituted by joining the 6th lens with the 7th lens. The lens system is made satisfy formulas I -VI [f: the focal distance of the whole system, f1,2,3: the composite focal distance of the 1st-3rd lenses, ni: refractive index of d-line of the i-th lens, ri: radius curvatures of the i-th surface, di: an interval between the i-th surface and the (i+1)th surface].
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