| 摘要 |
PURPOSE:To detect easily detection of a defective mark of a defective sector at data reproduction by providing a means to check a defect of a sector, a means writing a defect mark, a means detecting a defective sector mark and a means replacing a sector. CONSTITUTION:An optical head 3 irradiates a uniform light in a degree not being recorded on an optical disc 1, receives its reflected light, outputs a reproducing signal 100, which is amplified by a reproduction circuit 5 and enters a defect detection circuit 8 as a signal 120 while being subject to filtering processing at a frequency band suitable for detection of a defect of the disc. A defect exceeding a prescribed slice level is fed to a cpu 9 as a dropout signal 130, and whether or not it is a defective sector is discriminated depending on the length and its number. When it is discriminated as a defective sector, the cpu 9 sends a start signal 140 to a defect mark generating/detecting circuit 7, outputs a defect mark signal 150 to a recording circuit 4, where the mark signal is marked on the corresponding sector.
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