High density recording on a dual layer phase change disk with PRML method

We have previously reported experimental results of a high density recording and reproducing technology of over 25 GB capacity/side using high NA objective lens, a thin cover layer, blue laser diode, and partial response maximum likelihood (PRML) method (S. Furumiya et al, Tech. Digests ODS2001; M. Shoji et al, Tech. Digest, ISOM2001). However, larger capacity is desired for a digital video recording system for HDTV. In this paper we present 50 GB or more capacity/side recording on a dual-layer phase change disk with the PRML method.