| 摘要 |
PURPOSE:To set the neutral position of an objective lens in focus direction magnetically with simple constitution by fixing a permanent magnet to a rotor and also providing a neutral position setting member made of a magnetic material to a slider side. CONSTITUTION:An objective lens 4 is fixed to a rotor 20 made of nonmagnetic material turnable around a guide shaft 5 with eccentricity and two permanent magnets 22 are fitted to the lower part of the rotor 20. A focus direction drive coil 7 and a track direction drive coil 8 are fixed to an inner cylinder wall 24 of a slider 3 and also a neutral position setting member 30 made of a magnetic material is fixed to the lower part of a guide shaft 5. Since the magnetic flux line of the permanent magnet 22 passes through the setting member 30, the permanent magnet 22 receives a force so as to make the upper and lower magnetic flux uniform and the rotor 20 is moved to the neutral position in the focus direction. Thus, the focus neutral position of an objective lens 4 is set simply magnetically. |
