| 摘要 |
PURPOSE:To enlarge an illuminating area on a recording medium and to always exactly read information regardless of the size of a track width by arranging a light source with being dislocated from the focus position of a collimator lens and illuminating a recording medium in a defocus condition. CONSTITUTION:A semiconductor laser 2 is mounted to a lens frame 9 so that the length-wise direction of a reading light in a cross section ellipse shape to be outgoing from the semiconductor laser 2 can be the width direction of a track and an emitting point 2a can be positioned in this side slightly from a focus position 3a to a collimator lens 3. A diaphragm 4 is symmetrically arranged so as to respectively shade one part of a part to correspond to the photo-detecting area of an optical detector 8 in the short axis direction of the reading light in the cross section ellipse shape. Thus, on an optical card 1, the reading light is irradiated in the defocus condition and the illuminating area goes to be a size to enough illuminate the track of the optical card 1. Then, the information to be recorded in an optical recording medium can be always exactly read. |
