An illuminator for uniformly illuminating an entrance pupil of an inspection system in order to increase inspection resolution and sensitivity and improve system-to-system matching is described. The illuminator incorporates at least two lightpipes for spatially and angularly distributing light rays from the illuminator uniformly across the entrance pupil. The illuminator also results in spatial and angular uniformity at the field stop plane. In one embodiment, one lightpipe has a circular shape and a second lightpipe has a rectangular shape.