OPTICAL HEAD DEVICE, OPTICAL INFORMATION DEVICE, COMPUTER, DISC PLAYER, CAR NAVIGATION SYSTEM, OPTICAL DISC RECORDER, AND VEHICLE

摘要

Provided is an optical head device capable of coping with optical discs of different types and assuring a sufficient dynamic range for a low-density optical disc. An optical head device includes: a plurality of light sources which are switched from one to another for use; an objective lens for converging light emitted from one of the light sources onto a recording surface of an optical disc; and a photo detector for receiving the light reflected from the recording surface and outputting a focus error according to the light reception amount. In the optical head device, a defocus detection range of a focus error signal obtained according to light of the first wavelength light is set wider than a defocus detection range of the focus error signal obtained according to light of the second waveform.