| 摘要 |
PURPOSE:To reduce a remaining unerased part with the use of the single light source of a simplified optical system by setting distribution in which an erasing beam spot irradiating a recording thin film is formed longer in a direction of recording track and formed in almost triangular shape having an apex angle and photoirradiation power density is heightened successively advancing the almost triangular apex angle by the erasing beam spot. CONSTITUTION:A light beam transmitting a lens 9 for beam formation and irradiating the plane of an optical disk 8 goes to a triangular shape erasing beam a1 whose apex angle is extended in the direction of the recording track 10. As for temperature change received by one recording part of a rotating optical disk 8 by the erasing beam a1, a temperature rises steeply at a triangular apex angle part with high light power density where the light beam is sufficiently stopped first, and the recording thin film of the optical disk 8 arrives at a soluble point Tm, and after that, the light beam moves to a part with the wide spot area of low light power density of the light beam, and the temperature falls gradually, then, it is crystallized. In such a manner, a crystallized state almost similar to the crystallization at an unrecorded part can be produced by which erasure is surely performed. |
