| 摘要 |
A DISC PLAYBACK APPARATUS FOR PLAYING BACK A DISC (10) ON WHICH DATA HAVE BEEN RECORDED UNDER A CLV CONTROL IS PROVIDED WITH A CLV CONTROL SECTION (1) FOR PERFORMING A CLV CONTROL, A SPEED COMPARATOR (2) AND A REFERENCE CLOCK GENERATOR (3) FOR PERFORMING A CAV CONTROL, A CHANGEOVER SWITCH (4) FOR SWITCHING BETWEEN THE CLV CONTROL AND THE CAV CONTROL, AND A CPU (6) FOR SETTING A SWITCHING POINT OF THE CHANGEOVER SWITCH (4) AND CONTROLLING THE SWITCHING OF THE CHANGEOVER SWITCH (4). ACCORDING TO ANOTHER ASPECT OF THE INVENTION, SWITCHING IS MADE BETWEEN A PLAYBACK WITH A CLV SERVO CONTROL AND A PLAYBACK WITH A CAV SERVO CONTROL IN ACCORDANCE WITH THE REPRODUCTION SCANNING POSITION IN THE DISC RADIAL DIRECTION. IN PARTICULAR, A DIFFERENCE BETWEEN DISC ROTATION SPEEDS AT THE DISC INNERMOST AND OUTERMOST TRACKS IS MADE SMALLER THAN THAT IN A CASE WHERE A PLAYBACK IS PERFORMED AT A SPECIFIC LINEAR VELOCITY OVER THE DISC ENTIRE AREA. ACCORDING TO A FURTHER ASPECT OF THE INVENTION, REGIONS ARE SET BY DIVIDING THE DISC ENTIRE AREA IN THE DISC RADIAL DIRECTION. A JUDGMENT IS MADE OF A REGION TO WHICH A CURRENT REPRODUCTION SCANNING POSITION BELONGS, AND CONTROL IS MADE SO AS TO SWITCH THE PLAYBACK LINEAR VELOCITY IN ACCORDANCE WITH THE REGION THUS DETERMINED. IN PARTICULAR, A DIFFERENCE BETWEEN DISC ROTATION SPEEDS AT THE DISC INNERMOST AND OUTERMOST TRACKS IS MADE SMALLER THAN THAT IN A CASE WHERE THE LINEAR VELOCITY IS NOT CHANGED OVER THE DISC ENTIRE AREAFIGURE 4
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