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Abstract

Abstract PURPOSE:To lighten remarkably the limit related to Abbe number, and to correct satisfactorily a spherical aberration by using a joint lens consisting of a biconvex lens of an object side, and a negative lens stuck to its image side, and forming its joint surface to an aspherical surface. CONSTITUTION:When Abbe number in a (d) line of a biconvex lens, and that of a negative lens are denoted as nupd and nund, respectively, it is necessary to satisfy 10<nupd-nund. Also, it is desirable to satisfy a condition of 0.8<r1/(np-1) f<1.4 (r1:np: and (f) denote a radius of curvature of the top of the surface of an object side of a positive lens, a refractive index of the positive lens, and a focal distance of the combined system). Moreover, it is desirable to satisfy 0.2< (np-1){1-nund/nupd)} with regard to the refractive index np of the positive lens. The condition is a condition related to a difference of Abbe number of the positive lens and the negative lens in this case.

Inventors

• 👤 Norikazu Arai
• 👤 則一 荒井

Bibliographic Details