Measurements of surface defects on optical components

An objective scanning optical microscope technique to inspect the surfaces of optical components for imperfections (ranging from sub-micrometre to several micrometres in size) would replace the subjective methods currently in use by human quality controllers. Some laboratory microscope systems have been developed but they are too expensive and complex to be used on production lines. The atomic force microscope, with its image analysis software, has proved to be ideal for characterizing scratches and digs which, it is hoped, will assist the development of simpler optical microscope systems. The atomic force microscope images are repeated by the scanning electron microscope micrographs and both have their particular merits. The Form Talysurf was found to have insufficient resolution for the smallest unacceptable scratches and digs but could measure the waviness and form of large components.