| 摘要 |
PURPOSE:To surely erase information with a low power and less thermal damage without leaving information unerased by continuously projecting a first elliptic erasing light spot, whose lengthwise direction is approximately orthogonal to a recording track, and a second elliptic erasing light spot, whose lengthwise direction coincides with the direction of the recording track, in order. CONSTITUTION:The first elliptic erasing light spot a1 is so arranged that its lengthwise direction is orthogonal to a recording track 1, and the second elliptic erasing light spot a2 is so arranged that its lengthwise direction is on the same line as the recording track 1. When two erasing light spots a1 and a2 are projected to the same track and a disc is rotated, the temperature of an irradiated part quickly rises by the first erasing light spot a1 to melt the irradiated part and this part is cooled and solidified, but cooling is retarded by the second erasing light spot a2 and the irradiated part is kept at a temperature higher than the crystallization temperature for a long time, and therefore, the amorphous part is set to the crystalline state to complete erasing. Thus, information is erased with a low power and less thermal damage without being left unerased. |
