| 摘要 |
An indicator lamp comprising a first, thin-film interference filter (14) located in front of a light source (10) for rejecting undesirable near infra-red radiation originating from the light source, and a second filter (12) located on the opposite side of the filter (14) to the light source for absorbing radiation of predetermined undesired visible wave lengths from the ambient external light and ambient external light reflected by the filter (14). The second filter can be a neutral density filter, a circularly polarising filter or simply an absorbtion filter. <IMAGE> |
