Artificial illumination device

Artificial illumination device for generating natural light similar to that from the sun and the sky with making an observer experience a visual infinite-depth perception of a sky and sun image when the observer directly looks at the artificial illumination device, comprising:

• a direct-light source which comprises a first light-emitting device and a first emitting surface and is configured so that the direct-light source produces a direct light with a luminance profile Ldirect(x, y, which comprises—with respect to angular dependence on polar angle θ—a narrow peak in the angular distribution around a direct-light direction of half width at half maximum θHWHM≦5°, and a low background such that for polar angles θ>3θHWHM Ldirect drops below 10% of an absolute maximum of Ldirect over all positions and angles, and wherein Ldirect(x, y, θ, φ) is—with respect to spatial coordinates—uniform across the first emitting surface so as to avoid visual perception cue conflicts, and
• a diffused-light generator which is positioned downstream of the first light-emitting device, is at least partially light-transparent, and is configured to cause diffused light at a second emitting surface, wherein one of the first emitting surface and the second emitting surface is positioned downstream with respect to the other or both coincide to form a outer emitting surface of the artificial illumination device,
• and wherein the artificial illumination device is configured such that the direct-light source and the diffused-light generator co-operate to form outer light at the outer emitting surface which comprises a first light component which propagates along directions comprised within the narrow peak and a second light component which propagates along directions spaced apart from the narrow peak, wherein the first light component comprises a correlated color temperature which is at least 1.2 times lower than a CCT of the second light component,
• and wherein the diffused-light generator is configured to emit the diffused light over a solid angle which is at least 4 times larger than the narrow peak so that it affects a visual appearance of the artificial illumination device for the observer when directly looking at the artificial illumination device by creating a diffuse luminous bluish background around the low CCT bright spot created by the narrow peak in the luminance profile of the direct-light source, the diffuse luminous bluish background being uniform with respect to spatial coordinates.

Artificial illumination device for generating natural light similar to that from the sun and the sky with making an observer experience a visual infinite depth perception of a sky and sun image when the observer directly looks at the artificial illumination device, comprising:

• a direct-light source;
• and
• a diffused-light generator,
• wherein the direct-light source comprises a first light-emitting device configured to emit a primary light, and a first emitting surface positioned downstream the first light-emitting device,
• wherein the diffused-light generator is at least partially light-transparent and is positioned downstream of the first light-emitting device and comprises a second emitting surface and is configured to cause diffused light at the second emitting surface,
• wherein the direct-light source is configured so that, with the diffused-light generator being removed if positioned upstream of the first emitting surface, the direct-light source produces from the primary light a direct light that exits the first emitting surface with a luminance profile Ldirect(x, y, θ, φ) which comprises—with respect to angular dependence on polar angle θ—a narrow peak in the angular distribution around a direct-light direction of half width half maximum θHWHM, the narrow peak being subtended by a solid angle smaller than 0.2 sr, and the luminance profile Ldirect(x, y, θ, φ), comprises a low background outside the narrow peak such that for polar angles θ>3θHWHM, Ldirect(x, y, θ, φ) drops below 10% of an absolute maximum of Ldirect(x, y, θ, φ) over all positions and angles, and wherein Ldirect(x, y, θ, φ), is—with respect to spatial coordinates—uniform across the first emitting surface,
• wherein one of the first emitting surface and the second emitting surface is positioned downstream with respect to the other and forms an outer emitting surface of the artificial illumination device or both the first emitting surface and the second emitting surface coincide to form the outer emitting surface of the artificial illumination device,
• wherein the artificial illumination device is configured such that the direct-light source and the diffused-light generator co-operate to form outer light at the outer emitting surface which comprises a first light component which propagates along directions comprised within the narrow peak along at least 90% of the directions subtending with polar angle θ<θHWHM, and a second light component which propagates along directions spaced apart from the narrow peak and spanning at least 50% of the angular region outside the narrow peak with axis directed along direction and half-aperture 3 times larger than θHWHM, wherein the first light component comprises a correlated color temperature which is at least 1.2 times lower than a CCT of the second light component;
• wherein the diffused-light generator is configured to emit the diffused light over a solid angle which is at least 4 times larger than the narrow peak, so that the diffused-light generator affects a visual appearance of the artificial illumination device for the observer when directly looking at the artificial illumination device, by creating a diffuse luminous bluish background around the low CCT bright spot created by the narrow peak in the luminance profile of the direct-light source, the diffuse luminous bluish background being uniform with respect to spatial coordinates so as to cause a difficulty for the observer to estimate a distance between the observer and the second emitting surface so that the narrow peak in the luminance profile forces the eyes of the observer to converge at infinity and the plane from which the diffused light is perceived to be originated is dragged to infinity as well, and the diffuse luminous bluish background supports the observer′ eyes' converging at infinity because of an aerial perspective visual cue, and the uniformity of Ldirect(x, y, θ, φ) with respect to the spatial coordinates avoids visual perception cue conflicts.