THE PATH FROM A DIGITAL VERSATILE DISC (DVD) USING A RED LASER TO A DVD USING A BLUE LASER

The next generation digital versatile disc(DVD) using a blue laser is required to have 15 Gbytes capacity so that it can reproduce motion pi cture expert group 2(MPEG2) video stream with a main profile at a high level format for a maximum of 133 min. To achieve this goal, further improvements are necessary in both the recording and the reproducing s ystems. For the recording system the authors developed a super: resolu tion recording material and an electron beam recording system. For the reproducing system the authors devised four technologies: a Viterbi d ecoder, a liquid crystal tilt servo system, a cross talk cancel system and a tangential adaptive equalizer. By combining these with a pick u p head of 430 nm wavelength/0.6 NA lens and a 0.6-mm-thick substrate, the authors confirmed sufficient tilt mar ins in the case of 12.7 Gbyt es (radial tilt margin: +/-1.61 degrees, tangential tilt margin: +/-0. 48 degrees). Our next target is to work on the 15 Gbytes capacity.