PURPOSE: To prevent generation of a ghost flare by an out-of-image plane luminous flux by constituting a 1st reflecting member of a prism which has an object side incident face, reflecting face, and exit face provided on a 2nd reflecting member side and is so formed as to totally reflect the out-of-image plane luminous flux from the object side incident face by taking a refractive index into consideration.

CONSTITUTION: The 1st reflecting member 11 is constituted of the prism which has the object side incident face, the reflecting face and the exit face provided on the 2nd reflecting member side and is so formed as to exit the intra-image plane luminous flux from reflecting face at the exit face and to totally reflect the out-of-image plane luminous flux from the object side incident face. Namely, the intra-image plane luminous flux 8 arrives at the image plane after reflecting twice, but the out-of-image plane luminous flux 6 enters to the 2nd reflecting member side exit face 14 of the 1st reflecting member 11 constituting of the prism at a large incident angle and, therefore, said flux totally reflects on said face and does not arrive at the image plane 5. The spacing between incident optical axes 9 and 10 of the two optical paths can be decreased to the small spacing equiv. to the spacing in the prior art at this time. The generation of the ghost frame is thereby prevented.