Patent ID: 7102827

Claim:
An eyepiece lens comprising: in order from an eye point side, a negative meniscus lens having a concave surface facing to the eye point side; a double convex lens; and a negative lens, diopter of the eyepiece lens being adjusted by moving the double convex lens along an optical axis, at least one surface of the double convex lens having an aspherical surface with positive refractive power getting weaker in accordance with increase in a distance to the surface from the optical axis, and the following conditional expressions being satisfied: 0.22 <d 2/ f 2<0.32 −4.2 <S 1<−2.6 0.2 <S 2<0.35 −1.2 <S 3<−0.3 where d2 denotes the thickness of the negative meniscus lens along the optical axis, f2 denotes the focal length of the double convex lens, S1 denotes a shape factor of the negative meniscus lens, S2 denotes a shape factor of the double convex lens, S3 denotes a shape factor of the negative lens, and each shape factor is expressed by the following expression: S =( re+rs )/( re−rs ) where re denotes a radius of curvature of the eye point side surface and rs denotes a radius of curvature of the object side surface, and when the surface is an aspherical surface, a paraxial radius of curvature is used for the calculation.