| 摘要 |
PURPOSE:To control the reading of information with a tracking error signal and to facilitate easy tracking, by distributing the 1st and 2nd tracking signal recording regions at the part belonging to the horizontal flyback time of the video signal on the center line of a track respectively. CONSTITUTION:Tracking signals 3011, 3012... as well as video signal parts 2011, 2012... are recorded on a track 101. When a light beam is set at the center of the track, the outputs given from two tracking signal parts 3001 and 3002 are equal to each other. Then it is pissible to increase either one of these two outputs more than the other if the light beam deflects on the track. When the beam deflects upward, the signal (a) becomes larger than the signal (b) as shown in figure (B). Therefore the difference between signals (a) and (b) becomes plus. While if the beam deflects downward, the signal (a) becomes smaller than the signal (b) as shown in figure (C). Then the difference between these two signals is minus. As a result, the deflecting direction is understood from the difference signal. Then the direction of the light beam can be controlled by means of the differential signal so that said differential signal is set at zero. |
