| 摘要 |
PURPOSE:To improve both C/N ratio and responsiveness by forming groups concentrically or spirally on the surface of a shape memory alloy. CONSTITUTION:For instance, a triangular group 2 is formed concentrically or spirally on the surface of a shape memory alloy 1 around a rotary center. The LD light which hits the sloping surface of the group 2 is reflected obliquely and does not go toward the incident direction. Therefore no return light exists, and the group 2 can be applied for both unrecorded bits and control of tracks. When the LD light is irradiated to the group 2 to heat the group 2 up, the alloy 1 has its original shape again. Then it is virtually impossible to discriminate the track of the group 2. The LD light irradiated to the track of the group 2 goes back in the direction substantially equal to the incident light. The N/C ratio of this returned light is increased extremely. |
