Observation optical device

摘要

An observation optical device comprises first and second focusing mechanisms, an association mechanism, and a reticle. The first focusing mechanism focuses an observation optical system. The second focusing mechanism focuses a photographing optical system. The association mechanism keeps the observation optical system and the photographing optical system in a focused state. The reticle is provided for focusing the observation optical system with a predetermined dioptric power during an operation of the association mechanism. The second focusing mechanism is constructed in such a manner that a measured dioptric power difference between a first dioptric power of an ocular lens system of the observation optical system and a second dioptric power of a combination of the observation optical system and the photographing optical system is cancelled.