OPTICAL HEAD DEVICE

摘要

PURPOSE:To obtain an optical head device capable of well detecting a tracking error. CONSTITUTION:The luminous flux emitted from a light source 11 is condensed to an information recording surface 20 by an objective lens 18 and the reflected luminous flux from the information recording surface 20 is introduced by a diffraction grating 15 disposed in an optical path from a light source 11 to the information recording surface 20 to a photodetector 23, by which detection or recording of information is executed. A collimator lens 12 which converts the luminous flux emitted from the light source 11 to parallel luminous fluxes and makes these parallel luminous fluxes incident on the objective lens 18 is disposed between the light source 11 and the objective lens 18 of the optical head device. The diffraction grating 15 is arranged into the optical path of the parallel luminous fluxes heading toward the objective lens 18 from the collimator lens 12 and the objective lens 18 is moved in a direction perpendicular to the optical axis, by which autotracking to the information recording surface 20 is executed.