(under subclass 216) Subject matter having optical means for acting unequally upon different frequencies of radiation in the optical path of light from a light source to the photocell.
(1) Note. Examples of such optical means, found in this subclass, are diffraction gratings, dispersion prisms and visible light filters.
SEE OR SEARCH THIS CLASS, SUBCLASS:
211, for similar subject matter, where the photocell has inherent selective color sensitivity.
239, for photocells which are provided with cooling means to absorb infrared rays.
361+, where the photocell is provided with means to enhance response to invisible radiant energy or diminish response to visible radiant energy, e.g., an ultraviolet filter.
