Embodiments of the present disclosure relate to an apparatus for thermally processing a semiconductor substrate. In one embodiment, the apparatus includes a substrate support, a beam source having a fast axis for emitting a beam along an optical path intersecting the substrate support, and a homogenizer disposed along the optical path between the beam source and the substrate support. The homogenizer comprises a first lens array, and a second lens array, wherein lenses of the second lens array have a larger lenslet array spacing than lenses of the first lens array.