A stereolithography apparatus , having an exposure arrangement comprising: - a radiative element , for emitting optical radiation, - a masking element , having a substantially rectangular masking area , for forming an exposure pattern by partially masking optical radiation from the radiative element , - an optical path between the radiative element and the masking area , the optical path having a linear segment , and - an intensity-unifying arrangement , having reflective surfaces, the reflective surfaces having a third and a fourth reflective surface (152 3 , 152 4 ); wherein the third and fourth reflective surfaces (152 3 , 152 4 ) are arranged on opposite sides of the linear segment ; the reflective surfaces (152 3 , 152 4 ) are configured to collect optical radiation from the radiative element , propagating obliquely with respect to the linear segment , onto the masking area ; for each of the reflective surfaces (152 3 , 152 4 ), a distance , perpendicularly measurable from the linear segment , is non-decreasing with increasing distance along the optical path from the radiative element ; a cross section of the third and fourth reflective surfaces (152 3 , 152 4 ) along a plane, extending parallel to the linear segment and perpendicular to the third and fourth reflective surfaces (152 3 , 152 4 ), has a shape of a part of a conic section, e.g., a circle, ellipse, parabola, or a hyperbola; characterized in the reflective surfaces of the intensity-unifying arrangement having a first and a second reflective surface (152 1 , 152 2 ); the first and second reflective surfaces (152 1 , 152 2 ) are arranged on opposite sides of the linear segment ; the first and second reflective surfaces (152 1 , 152 2 ) are substantially planar; and in a cross section of the intensity-unifying arrangement along any plane, perpendicularly intersecting the linear segment , the reflective surfaces (152 1 , 152 2 , 152 3 , 152 4 ) follow a boundary of a rectangle. - a radiative element , for emitting optical radiation, - a masking element , having a substantially rectangular masking area , for forming an exposure pattern by partially masking optical radiation from the radiative element , - an optical path between the radiative element and the masking area , the optical path having a linear segment , and - an intensity-unifying arrangement , having reflective surfaces, the reflective surfaces having a third and a fourth reflective surface (152 3 , 152 4 ); wherein the third and fourth reflective surfaces (152 3 , 152 4 ) are arranged on opposite sides of the linear segment ; the reflective surfaces (152 3 , 152 4 ) are configured to collect optical radiation from the radiative element , propagating obliquely with respect to the linear segment , onto the masking area ; for each of the reflective surfaces (152 3 , 152 4 ), a distance , perpendicularly measurable from the linear segment , is non-decreasing with increasing distance along the optical path from the radiative element ; a cross section of the third and fourth reflective surfaces (152 3 , 152 4 ) along a plane, extending parallel to the linear segment and perpendicular to the third and fourth reflective surfaces (152 3 , 152 4 ), has a shape of a part of a conic section, e.g., a circle, ellipse, parabola, or a hyperbola; characterized in the reflective surfaces of the intensity-unifying arrangement having a first and a second reflective surface (152 1 , 152 2 ); the first and second reflective surfaces (152 1 , 152 2 ) are arranged on opposite sides of the linear segment ; the first and second reflective surfaces (152 1 , 152 2 ) are substantially planar; and in a cross section of the intensity-unifying arrangement along any plane, perpendicularly intersecting the linear segment , the reflective surfaces (152 1 , 152 2 , 152 3 , 152 4 ) follow a boundary of a rectangle. <EOS>