Optical filter and artificial light illumination device for reproducing the light of the sky and the sun using the same

Abstract

The present invention refers to an optical filter () comprising an inlet surface () and an outlet surface () which are substantially flat and parallel, a plurality of locally planar and mutually locally parallel visible light absorbing sectors () extending between the inlet surface () and the outlet surface () for a sector length (L), and a plurality of solid transparent sectors () made with at least one solid material transparent to visible light, each transparent sector () of the plurality of transparent sectors being interposed between two absorbing sectors () to create an alternation of transparent sectors () and absorbing sectors () adjacent to and in contact with each other, wherein each visible light absorbing sector () of the plurality of visible light absorbing sectors () borders at most two transparent sectors () of the plurality of transparent sectors (), and/or wherein a distance between adjacent absorbing sectors () of the plurality of absorbing sectors () is substantially constant, wherein each transparent sector () of the plurality of transparent sectors is locally arranged and configured to have such a refractive power that, given a first collimated light () which impinges on the inlet surface () along an incidence direction (D) at a local region of the inlet surface (), the transparent sector () focuses the first collimated light () along a first focal line () orthogonal to a local plane of incidence (P), and/or gives a second collimated light () which impinges the outlet surface () along an incidence direction (D) at a local region of the inlet surface (), the transparent sector () focuses the second collimated light () along a second focal line () orthogonal to a local plane of incidence (P), wherein a plane orthogonal to the inlet surface () and containing a normal (N) to an absorbing sector () of the plurality of absorbing sectors D at the local region of the inlet surface () defines the local plane of incidence (P), and the intersection between the local plane of incidence (P) and the surface of an absorbing sector () defines the incidence direction (D) substantially common to the whole inlet surface ().