Objective optical element and optical pickup apparatus

摘要

A first phase structure corrects at least one of a spherical aberration due to a difference between a protective substrate thickness t 1 and a protective substrate thickness t 2 and a spherical aberration due to a difference between a first wavelength lambda 1 and a second wavelength lambda 2 , and a second phase structure corrects at least one of a spherical aberration generated when the first wavelength lambda 1 is changed in a range of ±10 nm, a best image point movement generated when the first wavelength lambda 1 is changed in a range of ±10 nm, and a spherical aberration generated when environmental temperature is changed.