| 摘要 |
Optical axis as central axis is defined as z-axis, and axes perpendicular to z-axis are defined as x- and y-axis. Metallic flat plates are formed parallel to x-z plane to overlap each other and be separated by a given distance. Multiple flat plates except the top flat plate and bottom flat plate are each provided with multiple through holes. Central flat plates are each provided with through holes of a first radius. Intermediate flat plates arranged between central flat plate and top flat plate and between central flat plate and bottom flat plate are each provided with through holes of a second radius smaller than first radius. Second radius of through holes formed in an intermediate flat plate arranged in a position farther from central flat plate is smaller than second size of through holes formed in an intermediate flat plate arranged in a position closer to central flat plate. |
