Disclosed is an optical device (10) comprising a plurality of lenses (100) for projecting a plurality of parallel beams (202, 204) having a predetermined width towards an object area, wherein each lens comprises a lens body including a cavity (150) for housing a solid state lighting element (200); a pair of opposing internally reflecting side surfaces (130) for constraining said beam within said predetermined width; and a light exit surface delimited by said opposing side surfaces, the light exit surface comprising a curved region (110) extending from a first further side surface (141) extending between the opposing side surfaces and shaped to generate a collimated beam portion along an optical axis; and a stepped region in between the curved region and a second further side surface (142) extending between the reflecting side surfaces, wherein said steps are defined by a plurality of prismatic protrusions (120), each of said protrusions laterally extending between said opposing side surfaces. A luminaire including at least one such an optical device is also disclosed.