| 摘要 |
In a focus controlling method of a laser beam for an optical disk, achieving a stable focus drawing-in, lowering ill influences due to stray lights, detecting an electric signal, which is obtainable upon basis of a reflection light from the optical disk loaded, in advance, while executing a focus sweep operation of gradually approaching the laser to a recoding surface of the optical disk, at an unnecessary light detection gain being higher than a gain of normal operation, thereby counting a number of signals generated due to unnecessary lights; and thereafter, detecting the electric signal, which is obtainable upon basis of the reflection light from the optical disk loaded, and thereby conducting a focus drawing-in, by considering an electric signal, which is generated just after a number detected thereof reaches to the counted number of signals generated due to the unnecessary lights, to be a signal reflected from the recording surface of the optical disk loaded.
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