| CPC F21V 9/02 (2013.01) [F21V 3/0615 (2018.02); F21V 5/007 (2013.01); F21V 9/40 (2018.02); F21V 11/06 (2013.01); F21Y 2115/10 (2016.08)] | 22 Claims |
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1. A direct-light generator for sun-sky-imitating illumination devices configured for generating natural light similar to that from the sun and the sky, comprising:
a first emitting surface and
an array of light-emitting devices configured to generate a direct light which exits the first emitting surface along a direct-light direction, wherein the direct light exiting the first emitting surface has a luminance profile (Ldirect(x, y, θ, φ)) which has a peak in an angular distribution around the direct-light direction and is uniform across the first emitting surface,
wherein each light-emitting device comprises a light emitter having an emitting surface and at least a pair of collimation lenses illuminated by the light emitter, each pair of collimation lenses comprising
a pre-collimation lens comprising a light inlet surface facing the light emitter emitting surface and a light outlet surface, the pre-collimation lens being positioned proximal to the light emitter and
a collimation lens comprising a light input surface and a light output surface, the collimation lens being positioned distal from the light emitter,
the light emitter and the pre-collimation lens being housed in a hollow housing which is at least partially made of or internally coated with light absorbing material and has at least an aperture where the collimation lens is positioned,
wherein the pre-collimation lens of each pair of collimation lenses is configured to emit with a substantially angularly constant intensity within an emission cone and to uniformly illuminate a whole light input surface of the collimation lens of the pair of collimation lenses,
wherein, with the pre-collimation lens having a pre-collimation lens height (b2), and a base of the input surface of the collimation lens being spaced apart from a base of the inlet surface of the pre-collimation lens of a lenses distance (h), the ratio (b2/h) between the pre-collimation lens height (b2) and the lenses distance (h) is in the range of 0.2-0.8, in the range between 0.25-0.75, or in the range between 0.3-0.7; and/or
wherein, with the pre-collimation lens having a pre-collimation lens maximum width (b1) and the collimation lens having a collimation lens maximum width (C), the ratio (b1/C) between the pre-collimation lens maximum width (b1) and the collimation lens maximum width (C) is in the range of 0.3-0.85, in the range between 0.35-0.75, or in the range between 0.4-0.7.
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