Abstract: A glide head that can be coupled to a mounting base via a load arm includes a gimbal. A slider is coupled to the gimbal and includes an air bearing surface having a downward protrusion. The distance between the protrusion and a disc under test is substantially insensitive to changes in a height measured from a bottom of the mounting base to an upper surface of the disc. Furthermore, the protrusion can have a distal end extending downward such that a distance from the distal end to the disc under test is less than a distance from every other surface of the slider to the disc during operation of the glide head. The glide head can have a fly height that is substantially constant. Therefore, the glide head can provide more accurate and more uniform detection of outwardly projecting defects on the surface of the disc.

Abstract: A glide head apparatus for testing surface characteristics of a disc includes a gimbal, a slider and an actuator including a piezoelectric material disposed between the gimbal and the slider. A voltage applied across the piezoelectric material is controllable to cause the piezoelectric material to expand or contract depending on the applied voltage so as to vary the fly height between the slider and a disc under test. The fly height can be varied without substantially varying the linear velocity of the disc under test. Methods of testing surface characteristics of a disc using the glide head apparatus also are disclosed.