An apparatus is disclosed including: a light source; a Fresnel lens, and a lens array. The Fresnel lens is disposed upstream from the light source to collimate light output by the light source. The lens array is disposed upstream from the Fresnel lens to mix collimated light that is output from the Fresnel lens. The lens array includes a plurality of optical elements arranged on a substrate. Each optical element includes a respective first planar surface arranged to face towards a different respective portion of the Fresnel lens and a second convex surface arranged to face away from the Fresnel lens.