SMALL WIDEEANGLE LENS OF RETROFOCUS TYPE

摘要

PURPOSE:To produce a retrofocus type photography lens of high performance having a small size and a large apeature ratio by aranging eight groups of lenses in a special manner. CONSTITUTION:The focal length of the whole system is denoted at f; the radius of curvature of its order is denoted at ri; the thickness of the lens of jth order and the air spacing are denoted at dj; the refractive index of the lens of hth order is denoted at Nh; the Abbe's number of the lens of lth order is denoted at nul; and the composed focal length from the mth plane to the nth plane is denoted at fmto-n. There are arranged in the order from an object a negative meniscus lens 1, a positive lens 2, a lens 3 having both concave sides, a positive lens 4, an adhered positive lens 5, a lens 6 having both concave sides, a positive adhered meniscus lens 7 and a positive lens 8. Thus, it is possible to provide a lens of the desired object, which has a long foucs higher than 1.02 f, the total length shorter than 2.47f and the diameter of the front lens smaller than 0.9f.