OPTICAL INFORMATION REPRODUCTION METHOD, OPTICAL HEAD, AND OPTICAL DISC APPARATUS

摘要

An optical head which causes light used as reference light, not emitted onto an optical disc, to interfere with reflected light from the optical disc and obtains an amplified signal by calculation from a plurality of interference signal outputs, wherein coarse adjustment of differences in optical path length, adjustment of fixed position, and fine adjustment are carried out by separate means. Due to this, the optical head can easily and stably acquire an amplified signal and can improve the S/N ratio of a reproduction signal in cases when the signal light intensity has to be made weaker than in the past as is with multilayer optical discs which have a plurality of recording layers, and in cases when noise is increasing due to the signal reproduction rate becoming faster than in the past.