(a) Single nickel lens. The plate has dimensions 30 mm × 30 mm × 0.3 mm. The parabolic groove is pressed into the central part of the lens. The holes seen in the corners of the plate are used to assemble plates into a single compound lens. (b) Cross section of the parabolic groove obtained by cutting the lens sunk in epoxy resin. The light area in the image represents the Ni metal while the dark area is the epoxy. In the presented lens the thickness at the vertex is 2.5 µm.