Patent ID: 7962035

Claim:
A viewfinder optical system including an eyepiece optical system for observing a real image of an object formed by an objective lens through an erecting image forming member, the eyepiece optical system consisting of, in order from the object along an optical axis, a double concave negative lens, a double convex positive lens, a lens, and a meniscus lens having a convex surface facing the object; and wherein the following conditional expression is satisfied: 2.0<( G 4 RO+G 4 RE )/( G 4 RO−G 4 RE )<4.0 where G4RO denotes a radius of curvature of an object side surface of the meniscus lens having a convex surface facing the object, and G4RE denotes a radius of curvature of a pupil side surface of the meniscus lens having a convex surface facing the object.