OPTICAL ELEMENT AND OPTICAL HEAD DEVICE PROVIDED THEREWITH

摘要

Provided is an optical element which reduces the amount of stray light on an optical disk; also provided is an optical head device using said optical element. This optical element is divided into multiple regions on at least one surface, and is provided with a first region which collects light of a wavelength lambda1 on the recording surface of a first optical disk and collects light of a wavelength lambda2 on the recording surface of a second optical disk, and with a second region which is formed on the periphery of the first region and which collects light of the wavelength lambda1 on the recording surface of the first optical disk. In the second region is provided an uneven structure which is formed in concentric circles on an aspheric surface and which has a serrated cross-section. The uneven structure is configured from different serrated shapes, and each of the different serrated shapes imparts to light of wavelength lambda1 a different phase difference of an approximately integral multiple of the wavelength lambda1.