| 摘要 |
PROBLEM TO BE SOLVED: To improve precision in information recording and tracking at low cost in proximity recording by shaping the ruggedness of an optical spot guiding groove in a prescribed curved face relative to the horizontal direction and thereby sensitively detecting relation between a probe and the medium surface. SOLUTION: The surface of a recording medium is constituted of a semi-circular projected shape whose radius of curvature 1011 is 5 μm or less, eliminating a surface orthogonally crossing the incident direction of a convergent light source with respect to the medium radius direction, and setting the ratio of the pitch 1012 between the projected shapes to the radius of curvature in the range of 1 to 4. As a result, a distance 1021 between the probe and the medium surface sensitively changes against movement in the horizontal direction of the probe, actuating servo as a frequency or a phase shift signal. In this case, the semi-circular projected shape prevents malfunction due to sharp change, enabling highly precise tracking. Incidentally, the medium surface may be a periodic structure in a semi-circular recessed shape or a prescribed triangular projected shape. |
