A multilayer optical disk apparatus comprises an optical pickup that emits N (N represents an integer of two or more) laser beams of the same wavelength. The optical pickup emits the N laser beams at the same time, focuses the N laser beams on a first recording layer group alternately configured by N...http://www.google.de/patents/US8054728?utm_source=gb-gplus-sharePatent US8054728 - Multilayer optical disk, multilayer optical disk recording apparatus and multilayer optical disk reproducing apparatus
