Patent ID: 8022632

Claim:
An illumination device ( 1 ), comprising: a) at least one light emitter (L 1 , L 2 , L 3 , L 4 ); b) at least two photosensors (D 1 , D 2 , D 3 ) for measuring the light output of the light emitter (L 1 , L 2 , L 3 , L 4 ) over at least a portion of the spectral range thereof, wherein the sensitivity curves of the photosensors are distinct and oscillatingly extend over the spectral range of the light emitter (L 1 , L 2 , L 3 , L 4 ); c) a processing unit ( 14 ) coupled to the photosensors (D 1 , D 2 , D 3 ) for receiving measuring signals therefrom and determining a characteristic value of the light output of the light emitter (L 1 , L 2 , L 3 , L 4 ) based, at least in part, on the measuring signals; wherein the sensitivity curve oscillates between each two neighboring local maxima by an amount of at least 10% of the smaller of said two local maxima.