Abstract: The present invention describes a time based servo pattern scheme which provides position and velocity information with high accuracy. A plurality of servo lines are formed on a data disk extending from the inner track to the outer track. In the preferred embodiment of the present invention, these lines are employed as part of a buried servo scheme such that the entire useable disk surface is dedicated to data storage. The servo pattern is written on each side of the disk so that, if the disk were transparent, the respective servo lines would appear to intersect when viewed from above. Servo heads located on each side of the disk detect servo line crossings. By comparing the time difference between crossings of corresponding tracks on either side of the disk, the radial position of the heads can be determined. Therefore, even when nominal track centers do not fall on servo line intersections, their position can be determined accurately.

Abstract: The present invention describes a time based servo pattern scheme which provides position and velocity information with high accuracy. A plurality of servo lines are formed on a data disk extending from the inner track to the outer track, In the preferred embodiment of the present invention, these lines are employed as part of a buried servo scheme such that the entire useable disk surface is dedicated to data storage. The servo pattern is written on each side of the disk so that, if the disk were transparent, the respective servo lines would appear to intersect when viewed from above. Servo heads located on each side of the disk detect servo line crossings. By comparing the time difference between crossings of corresponding tracks on either side of the disk, the radial position of the heads can be determined. Therefore, even when nominal track centers do not fall on servo line intersections, their position can be determined accurately.

Abstract: The present invention utilizes a dual frequency data writing scheme. At a first frequency, flux transitions are achieved which result in large excursions of the information signal. In the preferred embodiment, the first frequency approximates the maximum frequency at which such excursions can occur. A second higher frequency is utilized to create the very small or no excursions. At this second higher frequency, a complex flux transition is not achieved. Therefore, there is little or no information signal. Information is represented by the presence or absence of excursions. In the preferred embodiment, the first frequency is approximately 33,000 flux changes per inch, and the second frequency is approximately 67,000 flux changes per inch. In order to detect data written by the present scheme, an adaptive, self-compensating scheme is utilized. The present invention utilizes an excursion detection scheme which is pattern and radii independent.

Abstract: A method and apparatus for performing adaptive calibration of a disk drive assembly and for determining an offset value to compensate for differences in servo head to data head distance from a nominal value. The present invention has particular application in a relative track count servo system where absolute track position is not known from a reading of the servo track itself. In the preferred embodiment, a single head assembly having both a data head and a servo head is utilized. The distance between the data head center and the servo head center must be known so that a disk written on one drive assembly can be read in another drive assembly. This distance is a nominal value but may vary due to manufacturing tolerances. In the present invention, both the data and servo heads are utilized to establish a servo anchor reference track and to determine an offset correction value to compensate for variations in the servo/data head spacing. A dual reference track architecture is employed on the disk surface.