A slit illumination device includes a first light-emitting element, a first diaphragm and a projection lens group. The first light-emitting element generates a primary illumination light. The first diaphragm has at least one opening and the first diaphragm is disposed on a light exit side of the first light-emitting element, wherein the opening is an elongate shaped opening. The projection lens group is disposed on a light exit side of the first diaphragm to converge the primary illumination light and project to an target object, wherein a distance from the first diaphragm to the projection lens group is greater than a focal length of the projection lens group at a light entrance side and smaller than 2 times of the focal length of the projection lens group at the light entrance side. The foregoing slit illumination device has advantages of simple structure, small size and longer depth of field of a projection beam and so on. A microscope system including the foregoing slit illumination device is also disclosed.一種裂隙照明裝置包含一第一發光元件、一第一光闌以及一投影透鏡組。第一發光元件用以產生一主照明光。第一光闌具有至少一開孔，且第一光闌設置於第一發光元件之一出光側，其中開孔為一狹長狀開孔。投影透鏡組設置於第一光闌之一出光側，以會聚主照明光並投射至一目標物，其中第一光闌至投影透鏡組之距離大於1倍投影透鏡組之一入光側焦距且小於2倍投影透鏡組之入光側焦距。上述裂隙照明裝置具有機構簡單、體積小且投影光束之景深較長等優點。同時亦揭露一種包含上述裂隙照明裝置之顯微鏡系統。
