RETRO-FOCUS TYPE LARGE APERTURE LENS

摘要

PURPOSE: To provide a retro-focus type large aperture lens composed of six lenses and capable of improving various aberrations even with a F number of about 1.2 and a back focus longer than 1.1f by making a third lens a meniscus lens whose concave surface confronts the object side. ;CONSTITUTION: A first lens L₁ is a positive meniscus lens whose convex surface confronts the object side, a second lens L₂ is a negative meniscus lens whose convex surface confronts the object side, a third lens L₃ is a negative meniscus lens whose convex surface confronts the side of image forming surface, a fourth lens L₄ is a negative meniscus lens whose convex surface confronts the object side, a fifth lens L₅ is a biconvex lens whose surface of intensive curvature confronts the object side and a sixth lens L₆ is a positive meniscus lens whose convex surface confronts the object side.;COPYRIGHT: (C)1994,JPO