(under subclass 351) Subject matter wherein the modifier includes at least two spaced adjacent modifying means each having at least two plane or curved surfaces of the type generated by a straight or curved line (the "generatrix"); the means so arranged relative to each other that (a) no two of the surfaces are generated by an extension of the same generatrix, (b) one of the surfaces of one means faces one of the surfaces of the adjacent means, and (c) light is able to pass both surfaces of each means and at least one of the surfaces in a direction parallel or tangent to its generatrix.
(1) Note. A "grid", for purposes of classification in this subclass, consists of at least two intersecting pairs of louvers.
(2) Note. The two spaced adjacent means of this subclass may be part of the same element, as for example, a U-shaped or spiral louver.
