OPTICAL ELEMENT OF LIGHT COLLECTION OPTICAL SYSTEM FOR OPTICAL PICKUP DEVICE, LIGHT COLLECTION OPTICAL SYSTEM, AND OPTICAL PICKUP DEVICE

摘要

Provided is an optical pickup device which has a reduced size and saves energy. An optical element suitable for such optical pickup device is also provided. The optical element has a center region and a peripheral region, collects an inputted luminous flux having a wavelength (λ1) to a protection layer thickness (tC) in the center region and to the position of a protection layer thickness (tA) and that of a protection layer thickness (tB) in the peripheral region, and the protection layer thicknesses satisfy the relationship of tAtCtB. Thus, the optical element can record and reproduce information on and from different information recording surfaces, while having a coupling element fixed, even for a BD having a plurality of information recording surfaces. The optical pickup device provided with such optical element is also provided.