| 摘要 |
<p>An optical device has a lens barrel integrated with an annular support member which is provided on its upper face with three projections. By these projections, the lower side of the parallel flat plate is supported at the three points and in direct contact with them. In this supported state, the parallel flat plate confronts the confronting face of the support member with a spacing of, e. g., several micrometers. As a result, the space on one side of the parallel flat plate is almost isolated from the space on the other side. Therefore, for example even if the spaces on both sides of the parallel flat plate are in different gas environments, the gases of the two can be effectively prevented from being mixed with each other. Moreover, the parallel flat plate is supported at the three points in one plane, so that the parallel flat plate does not deform by the supporting force supporting the parallel flat plate, thereby suppressing variation of the refractive index.</p> |
