de of an amorphous silicon or other material to make the test surface reflective and having a thickness between 1000 and 5000 ???; [0018] a support carries the optically active test stack, the support preferably made of nylon, track-etch polycarbonate, nitrocellulose, or polysulfone; [0019] the optically functional layer is coated with an antireflective layer having a thickness between 400 and 700