OPTICAL PICKUP DEVICE AND, OBJECTIVE OPTICAL UNIT AND OBJECTIVE OPTICAL SYSTEM DESIGNING METHOD

摘要

An optical pickup device comprising a first light source for outputting a first light beam, a second light source for outputting a second light beam, a third light source for outputting a third light beam, and an objective optical unit having an annular-structure first light path difference imparting structure and an annular-structure second light path difference imparting structure, wherein the magnifications of the objective optical unit when the first, second and third beams are incident to the objective optical unit are almost the same, the first light path difference imparting structure imparts a specified light path difference to the first light beam, and changes the spherical aberrations of all the first light beam, second light beam and third light beam to one of under and over directions, the second light path difference imparting structure imparts a specified light path difference to the first light beam, and changes the spherical aberration of only the second light beam out of the first light beam, second light beam and third light beam to the other direction different from the one of under and over directions.