| 摘要 |
PURPOSE:To achieve stable reproduction for the entire surface of disc, by forming the magnetic film on the surface of disc and providing the magnets on the reproducing unit opposed to the disc surface to make broad the focus control region, to keep constant the DC level in case of focus control. CONSTITUTION:A series of pits are arranged on the press forming disc 1 and metal such as Al is evaporated on the pit surface to form the reflection film 2. Further, the magnetic film 3 of Fe or its alloy is formed on the reflection film 2 with vacuum evaporation, and the protection film 4 is formed on the magnetic film 3. The disc 5 forming the magnetic film 3 is fixed to the flange 7 directly coupled to the motor of the reproducing unit 6. The front cover 8 of the reproducing unit 6 has the construction close to the surface of the disc 5 fixed and the high coersive force magnets 9 are located and fixed in ring shape at the part close to the disc circumference of the front cover 8, and only the disc circumference can be absorbed by shutting the front cover 8. It is also possible to change the height of the disc circumference by adjusting the coersive force of the magnets 9 and the distance with the disc 5. |
