| 摘要 |
PURPOSE:To continue a tracking control even if a drop-out is generated, by compensating a tracking control of a drop-out period basing on a pseudo beam position detecting output, and reproducing optically an information signal. CONSTITUTION:When an information signal is reproduced normally from a disk 1, a reproducing optical beam 14 and tracking beams 17, 18 scan a track 2, therefore, an output corresponding to a bit 6 is obtained from photoelectric converters 19, 20 and 43, and a normal beam position detecting output is generated from an error amplifier 27. When an absent part of the bit 6 is scanned by the optical beams 14, 17 and 18 in the course of reproducing, no normal beam position detecting output is generated from the error amplifier 27, but a drop- out detecting output is generated from a drop-out detecting circuit 46, by which a pseudo position detecting output is provided to a coil 32 in the same way as the normal beam position detecting output from a holding circuit 41, in the course of a drop-out period. |
