Objective optical element and optical pickup apparatus

摘要

An objective optical element of an optical pickup apparatus has a magnification m 1 satisfying the following formula for a light flux of the wavelength lambda 1 : - 1/7<=m 1 <=- 1/25 and |m 1 |<|M 1 , where M 1 is an optical system magnification from the first light source to the first optical information recording medium for a light flux of the wavelength lambda 1 . The objective optical element comprises a common region and an exclusive region. The exclusive region includes an exclusive diffractive structure having a function to suppress an increase of spherical aberration due to a raise of atmospheric temperature. A light flux of a wavelength lambda 2 having passed through the exclusive diffractive structure intersects with the optical axis at a position different from the position of the converged light spot formed on the information recording plane of the second optical information recording medium.