Abstract: The invention relates to a daylight illumination apparatus. A daylight collector (3) collects daylight (4), which is guided to an illumination location to be illuminated along an optical path by a light guide (5), wherein the daylight is absorbed by the light guide. A photoluminescent material (6, 8) is arranged within the optical path and emits photoluminescent light that compensates for the absorption of the daylight by the light guide. Absorption losses of the daylight can therefore effectively be compensated, without necessarily needing, for example, an active compensation light source. This allows providing compensated daylight illumination in a technically relatively simple way.

Abstract: The invention relates to a daylight illumination apparatus. A daylight collector (3) collects daylight (4), which is guided to an illumination location to be illuminated along an optical path by a light guide (5), wherein the daylight is absorbed by the light guide. A photoluminescent material (6, 8) is arranged within the optical path and emits photoluminescent light that compensates for the absorption of the daylight by the light guide. Absorption losses of the daylight can therefore effectively be compensated, without necessarily needing, for example, an active compensation light source. This allows providing compensated day-light illumination in a technically relatively simple way.

Abstract: The invention relates to a color-tunable illumination system (10), to a lamp and to a luminaire. The color-tunable illumination system comprises a light source (20) emitting light of a first predefined color (B), and comprises a luminescent material (30) for converting light of the first predefined color into light of a second predefined color (A). The color-tunable illumination system further comprises shielding means (40, 42) arranged for preventing at least part of the light emitted by the light source to impinge on the luminescent material. The light source, the luminescent material and/or the shielding means are changeable from a first situation to a second situation. In the first situation the color-tunable illumination system is arranged for shielding at least part of the luminescent material against impinging light of the first predefined color.

Abstract: A luminescent material includes erbium, gadolinium and an activator chosen from the rare earth elements and/or the transition metals. Upon excitation with radiation having a short enough wavelength, the luminescent material acts as a quantum cutter and has a quantum efficiency of more than 100%.