| 摘要 |
PURPOSE:To provide a novel method of recording and reproducing by alternately disposing substantially magnetic parts and nonmagnetic parts on the surface of a recording medium, recording information signals therein, applying a magnetic field, thereto and detecting the differences in the magnetic reluctance between the magnetic parts and nonmagnetic parts as current changes. CONSTITUTION:Pits 2 of 0.5- several mum lengths and 0.1-0.2mum depths are formed spirally or concentrically on a disc substrate 1 of a vinyl chloride base resin, and a magnetic material layer 3 of nickel metals or the like is formed on the surface thereof. Consequently, the inormation consisting substantially of magnetic raised parts and nonmagnetic recessed parts is recorded. A pickup consists of a magnetic body 31 having a gap 33, a coil 34 wound to this, a permanent magnet 32 and a nonmagnetic protecting member 38. When the disc rotates in an arrow (b) direction, the magnetic reluctance of the pickup changes in the magnetic parts and the nonmagnetic parts 2 and this change is detected as a change in the current of the coil 34. Thereby, the novel method of recording and reproducing is obtained. |
