| 摘要 |
PURPOSE:To detect accurately a tilt of an object by detecting the displacement due to a tilt of the object to a reference surface by means of the 1st reference sensor set at an intersecting point of two orthogonal axes together with the 2nd and 3rd sensors set on said two orthogonal axes. CONSTITUTION:A reference displacement sensor SS is set at an upper corner part corresponding to the intersecting point of a radial axis R and a jitter axis J of an optical base. At the same time, a displacement sensor SR for detection of radial direction tilt is set at a corner part on an orthogonal axis set along the axis R together with a displacement sensor SJ for detection of jitter tilt set at the corner part on an orthogonal axis set along the axis J respectively. These sensors are all set oppositely to the reflecting surface of a disk D. The sensors SS, SR and SJ consist of light reflectors, etc. together with a casing 20, a light emitting element 21 consisting of an LED set into the casing 20, and a photodetecting element 22 consisting of a photodiode, etc. |
