| 摘要 |
PROBLEM TO BE SOLVED: To record, reproduce and erase information in a simple optical system and to enable overwrite in erasing existing information and recording new information by changing power of an energy beam irradiating a recording medium between at least 1st, 2nd and 3rd levels. SOLUTION: A recording track of an optical disk medium having an In-Se system recording film capable of rewriting information by a crystal-amorphous- phase change is made to be in the amorphous state, while the crystal state is made between the recording tracks. When the optical disk medium is rotated, one light beam spot of laser beam with power at a reproducing level (1st level) irradiates the medium along a groove-like track to perform automatic focusing and tracking. At the same time as arrival in a place (A) of rewriting a record, the power is raised in a breath at a crystallization level (2nd level). At the time of arrival in a new recording place (B), the power is pulsewise raised at an amorphous formation level (3rd level). |
