Objective lens for optical pickup device, optical pickup device, and optical information recording and reproducing device

Abstract

Provided is an optical pickup device capable of ensuring the compatibility among three types of optical discs, i.e., BDs, DVDs, and CDs, with a common objective lens and, in addition, capable of ensuring a sufficient working distance for CDs, and also provided are an optical information recording and reproducing device and an objective lens suitable for the optical information recording and reproducing device. On the objective lens, there is arranged a first optical path difference providing structure formed such that: the direction of step differences of a basic structure wherein the diffraction order of a blue-violet laser light flux become an odd order faces toward the opposite direction of the optical axis; the direction of step differences of a basic structure wherein the diffraction order of the blue-violet laser light flux become an even order faces toward the optical axis; and both the basic structures are overlapped together.