Head flying height measuring apparatus

An apparatus for measuring the flying height of a head made to fly by directing an air flow over the surface of a rotating disk, the head having an air-bearing surface (ABS) adjacent to the surface of the rotating disk, wherein either the head or the disk has a transparent body and the other has an opaque body, said apparatus comprising:

• drive means for rotating said disk;
• means for positioning said head above the surface of said disk;
• a white light source;
• a first optical system for directing light from said white light source to the gap between said disk surface and said adjacent head ABS in such a way that said light is reflected a multitude of times by said disk surface and said adjacent head ABS;
• a photodetector array of pixel elements;
• a second optical system for directing said light reflected by said opaque body of either said disk surface or said adjacent head ABS to said photodetector array, whereby the light impacting the array of pixel elements is representative of light from a substantial portion of the head ABS;
• either said first optical system or said second optical system including an optical element for transmitting one at a time in a time-divisional way at least three components of said white light, each component occupying a particular wavelength region;
• and
• means for estimating the flying height of said head according to the least-square method from the averaged outputs of a plurality of adjacent pixel elements of said photodetector array on the basis of predetermined functions relating to said respective wavelength regions, each function correlating a disk-head gap with a reflected light intensity detected by said photodetector array.