| 摘要 |
PURPOSE:To eliminate the need for a high-output laser by recording modulated information while lowering laser power toward outer divided areas of an optical disk, making reproduction length shorter by the detection window width of a modulation system, and demodulating the information while correcting the period of a playback signal by the reciprocal of the direction window width during reproduction. CONSTITUTION:The positions of storage areas A and B of the disk are detected 17, a bias value 18 is mixed with a modulating signal to control the laser power, and information is recorded in the area B to length which is one clock shorter than the original length as shown by bits 55. When the information in the area B is reproduced, a corrected output signal 60 from an OR 25 through clock regeneration 23 and delay 24 is selected and when information in the area A is reproduced, the output signal 57 (uncorrected) of a waveform equalizing circuit 21 is selected to perform correct reproduction. Lastly, the modulated signal is demodulated by using the output of a switch circuit 26. In this constitution, even when the disk diameter increases to increase the linear speed at the outer periphery, the laser output is reduced and a high-output laser is not necessary.
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