Patent ID: 8342759

Claim:
A barrier unit comprising: a base; a pair of blades mounted on the base, the pair of blades being configured to be positioned in an open state and a closed state and to contact each other at predetermined end faces of the blades in the closed state; and a cover mounted on the base and having an opening through which an incident light passes, the blades being rotatably sandwiched between the cover and the base, wherein: an inclined portion is provided at a central portion in a longitudinal direction of each predetermined end face of the blades, the inclined portion being a flat plane inclined with respect to an optical axis of a lens; a parallel portion is provided on each predetermined end face of the blades on both sides of the inclined portion, the parallel portion defining a plane parallel to the optical axis; the opening of the cover includes a pair of straight portions parallel with each other; and a length of the inclined portion of each blade is longer than a length of each of the straight portions of the opening of the cover.