Patent ID: 8259555
Filing Date: 2012-09-04
Classification: G11B

Abstract:
1. An optical pickup for performing at least one of recording, reproducing, and erasing of information for at least two types of optical information recording media, the optical pickup comprising: an optical focusing system configured to focus a light beam from a light source onto a first recording layer of a first optical information recording medium via a first substrate having a first thickness t the optical focusing system comprises the plural regions comprise a center region comprising an optical axis, an outside annular region extending from a position of the first numerical aperture NA phase differences of the center region, the outside annular region, and the middle annular region are integral multiples of 2π with respect to a wavelength of the light beam; the steps having the uneven shapes are formed in a first annular region between the center region and the middle annular region and in a second annular region between the middle annular region and the outside annular region; and the steps are formed in such a manner as to reduce aberration that is caused by a difference between the first thickness t