Triplet lens having last diaphragm

Abstract

Abstract PURPOSE:To make a lens of about F4.0 have a value of an angle of field of 64 deg. or so, and also to reduce its binetting, by satisfying a prescribed condition in a triplet type lens. CONSTITUTION:A positive meniscus single lens whose convex surface has been directed toward an object side, a negative biconcave single lens and a positive biconvex lens are placed at small air intervals each in order from the object side. In an optical system where a diaphragm has been placed in the proximity of a lens in its image side, when f, fi, f1.2, di and SIGMAd denote a focal length of the whole system, a focal length of the i-th lens from the object side, a composite focal length of two lenses of the object side, the i-th surface space from the object side, and a surface space between the first surface and the sixth surface, respectively, in an optical system where a diaphragm has been placed in the proximity of a lens at its image side, the conditions of expression I - expression V are satisfied.

Inventors

• 👤 Shozo Ishiyama
• 👤 Ryoko Watabe

Bibliographic Details