(under subclass 213) Subject matter including an optical light attenuating member or members in the optical path which is illuminated from a location whose light intensity is to be determined, the members being adjustable or selectively placed in the optical path to control the illumination reaching the eye, the purpose being in both cases to reduce the visible illumination to render the viewed object or indicia markings barely visible.
(1) Note. See also (1) Note and the Search Notes under subclass 233 above.
SEE OR SEARCH CLASS
359, Optics: Systems (Including Communication) and Elements,
888, for neutral density filters, subclass 889 for filters movable in or out of the optical path, subclass 890 for filters superposed in series, and subclass 891 for filters in optical parallel.
