An optical system for producing uniform illumination on a target, comprising a lens body (204), a recess (202) formed on a bottom side of the lens body (204) at a central region thereof accommodating a light source arranged in an integration zone (206), the recess (202) having a side entry surface (208) and a central entry surface (210), a total internal reflection surface (212) provided at a side surface of the lens body (204), wherein the total internal reflection surface (212) comprises a plurality of first lenslets (216); and an exit surface (214) provided at a top side of the lens body (204), the exit surface (314) comprising a plurality of second lenslets (218), wherein each of the first lenslets (216) forms a pair (220) with each of the second lenslets (218), wherein the first lenslet (216) of the pair (220) focuses light from the integration zone (206) upon the second lenslet (218) of the pair (220), and wherein the second lenslet (218) of the pair (220) focuses the target upon the first lenslet (216) of the pair (220), such that the lens (200) produces uniform illumination on the target.