Study of error propagation due to dust for thin-cover coat disk systems

In recent years, optical disc systems with shorter wavelength laser diodes and higher numerical aperture (NA) objective lenses have been studied in order to realize higher storage density recording. However, high NA optical systems have the problem of an increase in coma aberration caused by disk tilt. It is necessary to use a thinner disk cover coating to achieve the same coma aberration margin as standard optical disc systems. Table-1 shows the optical parameters and the cover coat thickness of the optical disk systems up to date. However, the thinner cover coat disk systems entail the problem that dust and scratches on the disk surface cause data errors. In this study, we discuss the relationships between data error propagation and cover coat thickness, and between the error propagation and size of dust on the disk surface. We also discuss the abilities of error correcting codes (ECCs) against dust on the disks.