| 摘要 |
A lens assembly is provided that has an index-of-refraction invariant structure. In one embodiment, a void between two lenses or lens elements in a lens assembly is filled with a desired gas, liquid or vacuum, the gas, liquid or vacuum having a pre-determined index of refraction. Once the void has been filled with the desired gas or liquid or been drawn down to a complete vacuum, the void is sealed by any of numerous appropriate means to render it leaktight. The lens assembly may then be tested or calibrated to ensure an appropriate level of optical performance prior to subsequent deployment under actual field conditions. Because the vacuum or filled void disposed in the lens assembly provides optical performance that is index-of-refraction invariant, the lens assembly may be employed successfully under widely varying atmospheric conditions and yet still provide the same high quality results. |
