Many of us know that some optical filters are of a type called "dichroic". Unlike filters commonly used on lenses, they have very sharp cut-offs and are, for example, used as UV/IR blockers such as the B+W 486.
Not a new idea though! Watching an episode of Shatner's 'UnXplained' I learned today of a roman chalice made with "dichroic glass" !!
en.wikipedia.org/wiki/Lycurgus_Cup
Amazing, don't you think?
