The invention concerns a light source unit (1) of tunable spectral properties, having a pump light source (2) and a phosphor element (6) for a conversion of pump light (3, 5a-5c) into converted light intended for illuminating a target, wherein the phosphor element (6) comprises at least two phosphor element sections (6a-6c) interacting differently with pump light, and wherein the light source unit (1) further comprises a deflecting unit (4), such as a zoom lens or a variable diffraction grating, for deflecting the pump light (3, 5a-5c) so as to vary a distribution of pump light (5a-5c) incident onto the phosphor element (6) with respect to the different phosphor element sections (6a-6c), in order to vary spectral properties of the combined converted light beam emanating from the light source unit (1).本發明係關於一種具有可調光譜特性之光源單元(1)，具有一幫浦光源(2)及一螢光體元件(6)，用於將幫浦光(3,5a-5c)轉換為預定用於照射一目標的轉換光，其中螢光體元件(6)包括至少兩個與幫浦光作不同的相互作用的螢光體元件部(6a-6c)；且其中光源單元(1)另包括一偏折單元(4)，如變焦透鏡或可變繞射光柵，用於偏折幫浦光(3,5a-5c)，以改變入射到螢光體元件(6)上的幫浦光(5a-5c)相對於不同的螢光體元件部(6a-6c)之分布，從而改變從光源單元(1)出射的結合轉換光束之光譜特性。
