| 摘要 |
A top-power-increasing additional pulse is imparted to a portion of top power irradiation of a laser light beam, and a bottom-power-off pulse is imparted to a portion of bottom power irradiation of the laser light beam. Fine adjustment amount for the top power irradiation is modified roughly in accordance with a desired length of a pit to be formed, and the duration of the top-power-increasing additional pulse is adjusted finely. Fine adjustment amount for the bottom power irradiation is modified roughly in accordance with a desired length of a land to be formed, and the duration of the bottom-power-off pulse is adjusted finely. Further, timing to start the top power irradiation of the laser light beam is modified according to a desired length of a pit to be next formed; that is, the greater the next pit length, the more is delayed the top power irradiation start timing. In addition, timing to end the top power irradiation of the laser light beam is modified according to a desired length of a land to be next formed; that is, the greater the next land length, the more is advanced the top power irradiation end timing.
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