Patent ID: 6865032

Claim:
A real image type finder optical system comprising, in order from an object side thereof, an objective lens group having positive refracting power and an eyepiece lens group having positive refracting power, wherein: the objective lens group comprises, in order from an object side thereof, a first lens group consisting of a negative lens element, a second lens group consisting of a positive lens element, a third lens group consisting of a positive lens element and a fourth lens group having negative refracting power and forming a part of an image inverting optical system, wherein upon zooming from a wide-angle end to a telephoto end, the first lens group remains fixed, the second lens group and the third lens group move, and the fourth lens group remains fixed, the eyepiece lens group comprises, in order from an object side thereof, a fifth lens group that forms a part of an image inverting optical system and a sixth lens group having positive refracting power, and condition (1) is satisfied: 1.60< f b(w) /f w <3.0 (1) where f b(W) is a back focus of a composite system of the first lens group to the third lens group at the wide-angle end, and f w , is a composite focal length of the first lens group to the fourth lens group at the wide-angle end.