| 摘要 |
PURPOSE:To erase stably a record by giving to a recording medium at least two types of crystal structures in the solid state, holding the crystal structure inherent to one temperature area in the other one, and/or forming the recording medium with metal or alloy causing different volume changes in the crystal structure. CONSTITUTION:The recording medium 1 has at least two types of crystal structures in the solid state, holds the crystal structure inherent to one temperature area in the other one, and composed of the metal or alloy causing different volume changes in the crystal structure. A laser drive circuit 100 is set to each drive level by a signal 112 available from switching a mode by a write, erasure and reproduction mode setting circuit 110, and a laser beam 141 is set to the intensity corresponding to each level and shaped in a beam-like shape by an optical system 200, thereby forming a fine spot on the recording medium 1. A reflected light beam 204 from the recording medium 1 is detected by the photodetector 7 of the optical system 200, and attains a reflection 206. A reflected light intensity correcting circuit 120 corrects the intensities in write, erasure, reproduction modes, whereby a corrected and reflected light intensity 122 is outputted.
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