Optical filter and lighting device to reproduce the light of the sky and the sun comprising the same

Abstract

The present invention relates to an optical filter () comprising a substantially flat entry surface (), a substantially flat exit surface () parallel to the entry surface, a plurality of channels () made of a material substantially transparent to light, wherein the channels () of the plurality of channels comprise an entry face (), an exit face () and a lateral surface extending perimetrically between the entry face () and the exit face () over a length (L) of the channels (), are arranged side by side and parallel to each other so as to define a plurality of interspaces between adjacent channels (), have a channel axis (Y) incident to the entry () and exit () surface, and are arranged with the entry face () substantially overlapping the entry surface () and with the exit face () substantially overlapping the exit surface (), at least one element of optically absorbing and/or non-transparent material (') configured and arranged with respect to the channels () so as to reduce and/or substantially prevent the passage of light between adjacent channels () of the plurality of channels and so as to reduce the passage of light parallel to the channels and externally thereto, or at least a first element of optically absorbing material () configured and arranged with respect to the channels () so as to reduce and/or substantially prevent the passage of light between adjacent channels () of the plurality of channels () and at least a second element of optically non-transparent material (′) configured and arranged with respect to channels () so as to reduce and/or substantially prevent the passage of light parallel to the channels () and externally thereto through interspaces between adjacent channels (); wherein the channels () have a refractive index whose value decreases starting from a maximum refractive index (na) along a radially outward direction away from the channel axis (Y) passing through a centre of gravity of a section of the respective channel (), so as to define a radial profile of refractive index of the channels, and wherein the radial profile of refractive index of the channels () is configured such that the light rays crossing any channel () of the plurality of channels and belonging to a beam of rays emerging from any point on an edge of an entry face () of the channel exit the exit face () of the channel with substantially parallel directions.