Abstract: A method and apparatus for calibrating a flying height measurement instrument that: (1) precisely determines the actual height of a recording head over a disk, (2) is inexpensive, (3) permits the head whose flying height is to be measured to be used during the calibration procedure, and (4) is nondestructive to the calibration apparatus. In addition, the present invention can be used to calibrate different flying height measurement instruments and is independently verifiable. During the inventive calibration process, a special calibration slider is positioned over a measurement disk of a flying height measurement instrument in place of a slider which normally flies over the measurement disk when the flying height of a slider is being measured. The calibration slider has at least one support structure of a known height.

Abstract: Intensifier tubes for x-rays or low-light levels form an image of photoelectrons which is focused on a fluorescent viewing screen. Stray magnetic fields, including the earth's field, bend the electron trajectories and distort the image. Magnetic shielding has been used around the tube, leaving the image-receiving end open. Magnetic field leaking through the open end is reduced by extending the end of the shield around the image-receiving aperture inward and forward of the edge of the tube.