Phase correction element and optical head device

摘要

A phase correction element comprising a first phase correction layer formed in a region of numerical aperture NA2, and a first phase plate; the first phase correction layer comprising a concavo-convex portion having a rotational symmetry with respect to the optical axis of incident light and having a cross-sectional shape of a saw-tooth-form or a saw-tooth-form whose convex portions are each approximated by a step form; the first phase plate generating a birefringent phase difference of about an odd number times of &pgr;/2 for linearly polarized light of λ1; and the phase correction element that does change a transmitted wavefront of λ1 and changing a transmitted wavefront of the λ2 or transmitted wavefront of both wavelengths of λ2 and λ3 when three types of incident light at λ1=410 nm, λ2=650 nm and λ3=780 nm respectively, are incident.