Patent ID: 8325582
Filing Date: 2012-12-04
Classification: G02B,G11B

Abstract:
1. A complex objective lens for condensing a light beam onto an information recording surface of an optical disk having a base, comprising: an optical element having a relief structure on a surface thereof; and a refraction type lens, thereby condensing a first light beam having a wavelength λ wherein the relief structure of the optical element comprises a diffraction structure of a stepped cross-section in an inner circumferential portion near an optical axis and a diffraction structure composed of a plurality of sawtooth-shaped unit cross-sections in an outer circumferential portion outside the inner circumferential portion, in each of the sawtooth-shaped unit cross-sections, a boundary between the diffraction structure and an air is formed of two line segments, in which one of the line segments farther from an center axis of the complex objective lens is inclined so as to form an angle with respect to the optical axis larger than an angle formed by the other line segment with respect to the optical axis, a refractive surface of the refraction type lens is an aspherical surface on a side opposite to a side on which a light passed through the complex objective lens is condensed, and the optical element is formed integrally on the aspherical surface of the refraction type lens.