PROTRUSION DETECTING DEVICE FOR MAGNETIC DISK

摘要

PROBLEM TO BE SOLVED: To provide a protrusion detecting device which is managed without mounting a vibration sensor on a protrusion detecting head and is capable of detecting a minute protrusion with a satisfactory sensitivity. SOLUTION: In the protrusion detecting device of a magnetic disk in which the magnetic head floated from the surface of a rotating disk by air flow to be generated on the surface of the disk or a head equivalent to the magnetic head is made to be a detecting head and which detects the protrusion of a magnetic head by making the detecting head collide with a protrusion being on the surface, this device is provided with two-wavelength hetrodyne laser wavelength measuring devices 15, 16 which irradiate the surface of a side opposite to a plane at which a detecting head 8 is floated with a first laser beams and irradiate the surface of a disk 1 with a second laser beam and detect displacement amounts of disk 1 and the detecting head 8 by receiving respective reflected beams and a difference detecting circuit 17 which detects the detection signal of the displacement amount of the detecting head 8 and detects the detection signal of the displacement amount of the disk 1 and detects the difference between the detection signals and the device detects the protrusion of the disk 1 by comparing the output of the difference detecting circuit 17 with a prescribed reference value.