IMAGING LENS BY MEANS OF THREE LENSES

摘要

PURPOSE: To realize an imaging lens that is long in back focus, able to reduce an incident angle of an incident beam of light into a solid camera element, bright and wide in a field angle, in addition to being possible for miniaturization as well as to compensate any chromatic aberration by setting up a stop in the vicinity of a subject side end of a lens system, or at the more subject side than this end, and specifying an Abbe number of the most imaging surface side, in the case of three-lens constitution arranged in order a meniscus lens, a convex lens and a concave lens being weak in refractive power from the subject side. ;CONSTITUTION: This lens, consisting of three lenses L₁ to L₃, is made up of installing a stop (i) in a subject side end of the first lens L₁ or the more subject side than this end, and in this constitution, the first lens L₁ is of meniscus lens with weak refractive power directing a concave surface to the subject side, the second lens L₂ is of biconvex lens directing a strong curvature surface to the imaging surface side, and the third lens L₃ is of the meniscus lens with negative refractive power directing the concave to the subject side. In addition, these lenses satisfies a conditional expression of ν₃≤40. In this connection, ν₃ in this expression is set to an Abbe number of the third lens.;COPYRIGHT: (C)1995,JPO