A stereolithography apparatus (100) has an exposure arrangement (110), comprising a radiative element (120); a masking element (130), having a substantially rectangular masking area (132); an optical path (140) between the radiative element (120) and the masking area (132), having a linear segment (145); and an intensity-unifying arrangement (150), having a first, a second, a third, and a fourth reflective surface (1521, 1522, 1523, 1524) The first and second reflective surfaces (1521, 1522,) are arranged on opposite sides of the linear segment (145), and the third and fourth reflective surfaces (1523, 1524) are arranged on opposite sides of the linear segment (145). In a cross section of the intensity-unifying arrangement (150) along any plane, perpendicularly intersecting the linear segment (145), the reflective surfaces (1521, 1522, 1523, 1524) follow a boundary (156) of a rectangle.