| 摘要 |
A continuously-variable optical attenuator comprises two optical elements each arranged to be located on the axis of a beam of radiation with a plane surface perpendicular to the axis. Each element has a constant optical density in a first direction in the plane of the surface, and a continuously-variable optical density in a second direction perpendicular to the first direction. The continuously- variable optical densities of the two elements vary at the same rate but in opposite senses along the second direction. Means are provided for moving the two optical elements relative to one another in said second direction. |
