An illumination optical system for generating a line beam

An optical system for generating from a light beam of an intensity distribution on a surface (6, 88), said optical system comprising: - divides at least a first optical element (2, 10, 2 ', 10', 71) the incident beam (4, 89) into several beams (13, 91), some of them at least partially in a first direction on surface (6, 88) overlap; - at least a second optical element (22, 30, 31, 32, 33, 34, 40, 41, 44, 45, 46, 53, 77), at least one of the beams (13, 91) relative to a second of the plurality of beams (13, 91) in a second direction on the surface (6, 88) were added; characterized, in that the outer shape of the intensity distribution is rectangular and has a width between 3 and 100 microns in the second direction and a length in the first direction of greater than 300 mm; and that the second direction is perpendicular to the first direction.