Patent ID: 7366078
Filing Date: 2008-04-29
Classification: G11B

Abstract:
1. An optical pickup apparatus being capable of conducting information recording and/or information reproducing of at least a first optical information recording medium and a second optical information recording medium, each of which has a recording density different from each other, the optical pickup apparatus comprising: a first light source emitting a first light flux having a wavelength λ a second light source emitting a second light flux having a wavelength λ a light converging optical system comprising an objective lens, the light converging optical system comprising a first diffractive portion comprising a ring-shaped diffractive structure on at least one optical surface of the light converging optical system; and a photo detector, wherein in case the first light flux passes through the first diffractive portion to generate at least one diffracted ray, a light amount of a n-th ordered diffracted ray of the first light flux is greater than a light amount of any other ordered diffracted ray of the first light flux, wherein in case the second light flux passes through the first diffractive portion to generate at least one diffracted ray, a light amount of a n-th ordered diffracted ray of the second light flux is greater than a light amount of any other ordered diffracted ray of the second light flux, wherein n in each of the n-th ordered diffracted rays represents a common integer other than zero, and wherein a diffraction efficiency of the n-th ordered diffracted ray in the first diffractive portion becomes maximum for a light flux having a wavelength between λ