A type of visible-absorbing, infra-red transmitting filter is described in which the absorbing units are produced from a plastic film that also serves as a supporting medium. Filters of this kind prepared from polyvinyl chloride and polyvinylidene chloride films are characterized by transmission bands between 1 and 3.3μ and between 3.5 and 5.8μ. Ways of isolating either of these bands are described. Such filters have obvious utility in connection with photoconductive cells.
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