Objective optical system for endoscope and endoscope having same

Abstract

An objective optical system for an endoscope comprising, in order from the object side, a first lens unit G1 having a negative refractive power, a second lens unit G2 having a positive refractive power, and a third lens unit G3 having a positive refractive power. The first lens unit G1 includes a negative lens L1. The second lens unit G2 includes a positive meniscus lens L2 having a convex surface facing the image side. The third lens unit G3 includes, in order from the object side, an object side positive lens L3 and a cemented lens CL made up of a positive lens L4 and a negative lens L5. The second lens unit G2 is moved for focusing. The objective optical system satisfies the following conditional expressions (1) and (2): - 0 . 0 ⁢ 7 < f ⁢ 1 / f ⁢ 2 < - 0 .015 ( 1 ) - 0.4 < f ⁢ 1 / f ⁢ 3 < - 0 . 1 ⁢ 5 ( 2 ) where f1 is the focal length of the first lens unit, f2 is the focal length of the second lens unit, and f3 is the focal length of the third lens unit.

Dependencies are inferred from the claim text.