Hidekazu Nakamoto

257-nm optical disk cutting-machine

Many formats have been proposed and examined for next-generation DVD with a capacity of over 25 GB. Disk mastering is necessary for this purpose, and optical disk cutting-machines are key equipment for disk mastering. The laser wavelengths used in cutting-machines are getting shorter as the density of disk memory increases, and these wavelengths are shifting to the deep-UV (ultra-violet) range. We developed a 257-nm cutting-machine with an automatic realignment system for the laser beam and an effective AF (auto-focus) system for a non-dual wavelength objective lens. A 200 mW Ar-SHG laser is used as the laser source. The automatic realignment system consists of two sets of beam-position detectors and mirror actuators, and it is placed after the laser. An EOM (electric-optical modulator) is used as a noise-eater for each line, and a spatial filter is placed between AOM (acoustic-optical modulator) and AOD (acoustic-optical deflector) for wave-front correction.