| 摘要 |
PURPOSE:To expand the leading-in range of automatic of focusing control by coating the disk flank surface of a semiconductor laser with a reflection preventing film. CONSTITUTION:Optical pickup 12 consists of semiconductor laser 1, lenses 31 and 32, and photodetector 4, and laser beam is reflected out of optical disk 2 and fed back to emission end face 11 of semiconductor laser 1. Since the laser output varies with the reflectance of disk 2, the variation is detected by photodetector 4 to reproduce information. The laser output detected by photodetector 4 is synchronously detected by phase detecting circuit 8 by referring to an AC source signal and its output is fed back to electromagnetic coil 5 to reduce defocusing. Laser emission end face 11 is coated with a reflection preventing film, so that the leading-in range of automatic focusing control can be expanded. |
