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.