Effect of first information layer on second information layer in dual-layer disc

ABSTRACT For a dual layer structure, the effect of different physical geometries is studied using 0.65 and 0.85 ofnumerical aperture(NA), and this result gives an incitation for making a physical format for rewritable highdensity disc.Keywords : Dual layer, groove, pit, mark, defocus, geometry 1. INTRODUCTION As a need for recording a high capacity, for example, 2 hour or 135 minutes of high definitiontelevision(HDTV) is demanded, some new recordable media is essential. To fulfill the capacity of 2 hour or 135minutes of recording time, 23 GB to 25 GB per one side of 120 mm disc is necessary. In regard to thiscapacity, the current digital versatile disc(DVD), such as 4.7 GB DVD-random access memory(RAM) and 4.7GB DVD-rerecordable(RW) disc, does not meet the condition of large capacity. For achieving a higher densitythan that of rewritable DVD, some methods have been already proposed. For example, one of multi-layer disc 1 ,multi-level disc 2 , super- resolution 3 , hologram technology