Optical recording and reproducing methods for optical disk

An optical reproducing method for an optical disk having a disk surface portion in which wobble grooves indicative of rotation control sync information are formed to create a wobble signal, and prepits indicative of preformat information are formed to create a prepit signal, the optical reproducing method comprising the steps of:

• providing an automatic gain control AGC unit for each of photodiodes contained in a photodetector of a pickup, said AGC units being connected to the photodiodes, and each AGC unit providing a gain of a detection current output by a corresponding one of the photodiodes;
• detecting a portion of a data signal which matches one of the prepits and corresponds to one of write marks radially adjacent to said one of the prepits;
• detecting the wobble signal and the prepit signal along a track of the disk, using optimal gains of the AGC units, in accordance with a non-match portion of the data signal which does not match any of the prepits but corresponds to one of the write marks;
• and
• detecting the wobble signal and the prepit signal along the track of the disk, using reduced gains of a first half of the AGC units and the optimal gains of a second half of the AGC units, in accordance with the match portion of the data signal.

A wobble/prepit detection method for optical recording and reproduction of an optical disk having a disk surface portion in which wobble grooves indicative of rotation control sync information are formed, and prepits indicative of preformat information are formed, the wobble/prepit detection method comprising the steps of:

• detecting a portion of a data signal which matches one of the prepits and corresponds to one of write marks radially adjacent to said one of the prepits;
• detecting a wobble signal and a prepit signal along a track of the disk, using an optimal track offset, in accordance with a non-match portion of the data signal which does not match any of the prepits but corresponds to one of the write marks;
• and
• detecting the wobble signal and the prepit signal along the track of the disk, using a corrected track offset, in accordance with the match portion of the data signal, the corrected track offset having a margin of a prepit detection error to a permissible level, which margin being larger than a margin corresponding to the optimal track offset.