New high-accuracy electromagnetic measurement methods for read-write head alignment in floppy disk drives

This paper describes new techniques of measuring read-write head alignment that reflect a 5:1 improvement or greater over the conventional industry method of measuring the radial head spacing of double-sided diskette drives using cat's-eye diskettes. Measurement errors can be reduced further to nearly zero, based on calibrations with a laser interferometer. The new techniques are also being applied to measure and to correct for errors in “industry standard” cat's-eye diskettes; using the correction factors obtainable with these techniques, the “standard” diskettes can be used in the normal manner with greatly improved accuracies. Although these techniques were developed specifically for the 48 and 96 track-per-inch (tpi) 5.25-in floppy drives, they are applicable to any product that uses a double-sided read-write head assembly.