Optical disk drive.

摘要

In an optical disk drive which can reproduce signals of a high density, a laser beam emitted from a laser light source is converted to a parallel beam by a collimating lens, is shaded by a shading member as to the light around the axis, and is converged by an objective lens on a signal plane of optical disk. The distribution of the laser beam is located on a ring belt just after the passage of an aperture plane of the optical system. The feedbacked light is collimated by the objective lens and shaded again by the shading member around the optical axis to reach a beam splitter. The light reflected by the beam splitter is received through an optical system by a control signal detector, and focus signals and tracking signals on the signal plane of optical disk are detected. On the other hand, the light transmitting the beam splitter is detected by a detector. A primary or secondary differential signal is derived from the detected signal, and the edges or the center of the signal marks are reproduced by using the differential signal. <IMAGE> <IMAGE>