An optical unit for inspecting the state of latent images or photochromic images on a wafer is mounted on an exposure apparatus. Before actually printing images on a product wafer, a reticle pattern is printed on the wafer using a wafer on which a resist for development is coated or a photochromic film...http://www.google.com.hk/patents/US5162867?utm_source=gb-gplus-share專利 US5162867 - Surface condition inspection method and apparatus using image transfer
