OPTICAL INFORMATION DETECTOR

摘要

PURPOSE:To prevent a focusing error signal from the reduction of its quality by arranging an objective lens in a direction reducing a bad influence to be exerted upon a diffraction pattern of the aberration of the objective lens which is projected to a photodetector. CONSTITUTION:The objective lens 4 is fitted to an objective lens barrel 13 so as to be held on an objective lens holder 33 to be rotated around the lens barrel 13. After building an optical information detector in an objective lens driving device 12, the objective lens 4 is set up and fixed on a position reducing the influence to be exerted upon a diffraction pattern of the aberration of the objective lens 4 which is projected to the four-divided photodetector, concretely a position for symmetrizing the reduction of the photodetecting variable of the four-divided photodetector about a Y axis.