A unit magnification Wynn-Dyson lens for microlithography has an image field sized to accommodate between four and six die of dimensions 26 mm×36 mm. The lens has a positive lens group that consists of either three or four refractive lens elements, with one of the lens elements being most mirror-wise and having a prism-wise concave aspheric surface. Protective windows respectively reside between object and image planes and the corresponding prism faces. The lens is corrected for at least the i-line LED wavelength spectrum or similar LED-generated wavelengths.