| 摘要 |
PURPOSE:To prevent the performance of an optical disk from being deteriorated due to thermal damage and to secure a power margin in a wide range, by setting the maximum temperature of a recording film equally by each of erasing beams arranged in order. CONSTITUTION:To keep a recording bit 2 at a temperature over a temperature Tc where a state begins to change from an amorphous state to a crystal state for more than a prescribed time, the erasing beam is formed with two or more laser spots 5 and 6. And a beam power ratio is set so as to keep a peak temperature by each of the laser spots 5 and 6 equal. In such a way, it is possible to remove variance among the beams,and to secure the power margin to obtain the maximum critical temperature for crystallization with the same power in a wide range. Also, it is possible to prevent the performance of the optical disk from being deteriorated due to the thermal damage.
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