Optical pickup device, optical information recording and reproducing apparatus, expander lens, coupling lens and chromatic aberration correcting optical element

摘要

A spherical aberration correcting optical unit (EXP) is arranged between both of primary and secondary light sources and objective lens (OBJ). A chromatic aberration correcting optical element (PL) is arranged in common optical path of primary and secondary light fluxes, and has diffractive structure constructed by several ring-shaped zones separated by specially designed fine steps, that is formed on diffractive surface. Independent claims are also included for the following: (1) optical disk drive; (2) expander lens; (3) coupling lens; and (4) chromatic aberration correcting optical element.