| 摘要 |
PURPOSE:To detect a signal even in still state of a magnetic recording layer by providing a magnetic optical element for detecting magnetic flux which is leaked from a magnetic pitch, an irradiation means for applying a straight line polarization light to the element, and a first detection means for detecting the rotary state and a second detection means for detecting a traveling state. CONSTITUTION:Laser beam from first and second irradiation devices 26 and 28 allowed its polarization surface to be rotated due to reflection on first and second magnetic optical elements 22 and 24 and the rotary angle to be detected by detectors 30 and 32 of polarization surface by combining an analyzer and a photo detector. The direction of magnetization of the elements 22 and 24 is inverted according to magnetic flux which is leaked from a boundary part of the magnetic pitch. thus enabling the rotary angle of the polarization surface of laser beam to be also inverted. Therefore, by detecting the rotary angle using the controllers 30 and 32, the direction of magnetic pitch and phase can be detected. Namely, signal can be detected even if the magnetic recording layer is in still state, thus measuring load torque. |
