| 摘要 |
PURPOSE:To allow this system to adjust a focusing object by itself by varying the driving frequency of an acoustooptic element to cause aberration, moving a focus in both directions and detecting the out of focus from the shape of a light spot at this time. CONSTITUTION:The light spot on an optical disk 116 is minutely moved in the tracking direction by an acoustooptic element 104, and a convergence lens 112 is driven by a focus moving mechanism 114 and controlled so that the light spot is focused onto the disk 116. The light reflected in the optical disk 116 is reflected in a polarized beam splitter 106 through the convergence lens 112, a rising mirror 110 and a lambda/4 plate 108 and the reflected light beam is converged onto a detector 122 by a condenser lens 120, and a spot control signal detection circuit 124 detects the out of focus signal, an off-track signal and a data signal. |
