| 摘要 |
In a barrel of an optical unit a ring shaped support member is integrally arranged, and three projected portions are arranged on the upper surface of the support member. The projected portions support a lower surface of a parallel flat plate supported in direct contact. In this supported state, the parallel flat plate opposes a surface of the support member with a clearance of several mu m in between. With this arrangement, the space in one side of the parallel flat plate is substantially isolated from the space in the other side. Accordingly, for example, even if gas environment in the space on one side of the parallel flat plate is different from the other side, gases can be effectively kept from mixing. In addition, since the parallel flat plate is supported at three coplanar points, deformation of the parallel flat plate can be suppressed due to the force supporting the parallel flat plate, thereby suppressing the index of refraction from varying. <IMAGE> |
