A catadioptric optical system in which a first imaging optical system is constructed of a unidirectional optical apparatus which transmits outgoing light from a first plane in one direction only and a bidirectional optical apparatus for transmitting the light that enters and reflecting the same to form an interim image of the first plane. A light guide guides the light from the interim image to a second imaging optical system through which the interim image is reimaged on a second plane. The unidirectional optical apparatus has an optical axis and at least one lens movable along the optical axis.