Patent
Wide angle photographic lens
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TLDR
In this article, a small, light weight wide angle photographic lens has attachment size of less than approximately 3.5 times the focal length and has a field angle of approximately 100°.Abstract:
A small, light weight wide angle photographic lens has attachment size of less than approximately 3.5 times the focal length and has a field angle of approximately 100°. The wide angle photographic lens includes a first lens L 1 having a negative refractive power and a concave surface facing the image side; a second lens L 2 with a positive refractive power having the convex surface facing the object side; a third lens L 3 having a negative refractive power cemented to the second lens L 2 and having a surface with a larger absolute value of index of refraction on the image side; a fourth lens L 4 having a positive refractive power cemented to the third lens L 3 and having a surface with a larger index of refraction on the object side; and a plurality of lenses on the image side of the fourth lens L 4 , wherein the concave surface of the first lens L 1 is an aspherical surface with a conical constant κ greater than 0.3 and less than 0.3 with a curvature of the concave surface decreasing monotonically with increasing distance from the optical axis. The wide angle photographic lens also satisfies conditions 0<n 4 -n 3 <0.15 and 0.2<r 5 /f<0.7 where n 3 and n 4 denote the index of refraction of the third lens L 3 and the fourth lens L 4 , respectively, r 5 denotes the radius of curvature of the boundary surface between both lenses L 3 and L 4 , and f denotes the focal length of the total lens system.read more
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