| 摘要 |
PURPOSE:To record and reproduce stably a signal in a high frequency band by setting the state which a recording thin film attains under high temperature heating and quenching conditions as that where a signal is recorded and using the state attained under low temperature heating and slow cooling conditions as that where a signal is erased. CONSTITUTION:A recording medium 3 has at least two types of crystal structures in the solid state, holds the crystal structure inherent to one temperature area in the other temperature area, and/or composed of metal or alloy causing different volume changes in the crystal state. An incident beam a1 makes incident on the optical axis of a lens 10 in parallel, for instance, and a circular fine optical spot L1 is generated on the recording medium 3. On the other hand, an incident beam a2 makes incident on the medium with an angle theta against the optical axis of the stop lens 10, and an ellipsoidal fine optical spot L2 is generated along a groove on the recording medium 3. When the optical spot L1 is irradiated as a cyclic optical pulse in a short period on the optical recording medium, the heat of the medium is quickly propagated in its vicinity and cooled the moment the optical pulse disappears partially after temperature rising. When the optical spot L2 is irradiated as a continued time light beam, the recording medium is cooled far slowly after it is heated at a temperature theta2. |
