Patent ID: 7924507

Claim:
An eyepiece lens for observing an image formed by an objective lens via an erecting optical system, consisting of a first lens being a negative lens, a second lens being a positive lens, and a third lens being a negative lens, which are arranged in this order from an eyepoint side along the optical axis, in such a way that diopter adjustment can be carried out by moving at least one among the first lens, the second lens and the third lens along the optical axis, the first lens and the third lens having a biconcave shape, and a concave surface of the third lens on the eyepoint side having a curvature greater than that of a concave surface of the third lens on the object side; satisfying: 0.5< f 1/ f 3<0.8 wherein, f 1 is a focal distance of the first lens and f 3 is a focal distance of the third lens.