DISPOSITIVO DE CABEÇA ÓPTICA E ELEMENTO DIFRATIVO, APARELHOS DE INFORMAÇÕES ÓPTICO, COMPUTADOR, TOCADOR DE DISCO, SISTEMA DE NAVEGAÇÃO PARA AUTOMÓVEL, GRAVADOR DE DISCO ÓPTICO E VEÍCULO

摘要

In an optical head device compatible with optical discs of different tracking pitches, it is possible to obtain a tracking error signal based on an optimal DPP method by using a single diffraction element and suppress a tracking error signal amplitude lowering amount in the state when an object lens has moved for following the track. In the optical head device, grading phases at the left and the right domain (3101, 3102) of a sub-beam generation diffraction element (31) are different from each other by 180 degrees. The central domain (3109) of the sub-beam generation diffraction element has a grating pattern different from the left and the right domain (3101, 3102) and divided into a plurality of domains (3103, 3104) so that different gratings are formed.