F21V—FUNCTIONAL FEATURES OR DETAILS OF LIGHTING DEVICES OR SYSTEMS THEREOF; STRUCTURAL COMBINATIONS OF LIGHTING DEVICES WITH OTHER ARTICLES, NOT OTHERWISE PROVIDED FOR
F21V9/00—Elements for modifying spectral properties, polarisation or intensity of the light emitted, e.g. filters
F21V9/08—Elements for modifying spectral properties, polarisation or intensity of the light emitted, e.g. filters for producing coloured light, e.g. monochromatic; for reducing intensity of light