Servo head with varying write gap width

• US 20060044671A1
• Filed: 08/25/2004
• Published: 03/02/2006
• Est. Priority Date: 08/25/2004
• Status: Active Grant

• Current Assignee: Imation Corporation (Glassbridge Enterprises, Inc.)
• Original Assignee: Imation Corporation (Glassbridge Enterprises, Inc.)
• Inventors: Yip, Yung, Weber, Mark P.
• Granted Patent: US 7,199,958 B2
• Time in Patent Office: Days
• US Class Current: 360/77.120
• CPC Class Codes: G11B 5/584 for track following on tapes

Abstract

A servo head comprising a write gap with a non-uniform width is described. It allows non-uniform width servo marks to be recorded on magnetic media. A servo head having a non-uniform width gap may create servo marks that facilitate servo position error signal calculations using time-based methods, amplitude-based methods, or both. This invention provides alternative methods for positioning servo heads and may increase reliability and precision by allowing redundant calculations.

Claims

1. A data storage tape comprising a servo pattern, the servo pattern including a servo mark recorded by a non-uniform gap of a servo head, wherein a width of the servo mark defined in a down-tape direction is non-uniform across the tape.

2. The data storage tape of claim 1, wherein the servo mark has a trapezoidal shape, wherein the trapezoidal shape has exactly two parallel sides, the two parallel sides being parallel to an edge of the magnetic tape.

3. The data storage tape of claim 1, wherein the servo mark is a first servo mark, the servo pattern further comprising:

a second servo mark defining a substantially constant width of X; and

a third servo mark defining a substantially constant width of Y.

4. The data storage tape of claim 3, wherein the width of the first servo mark varies from X to Y.

5. The data storage tape of claim 1, wherein an amplitude of magnetization of the servo mark varies in a cross-tape direction as a function of the width.

6. The data storage tape of claim 5, wherein the width and the amplitude of magnetization vary substantially linearly in the cross-tape direction.

7. The data storage tape of claim 1, further comprising:

a servo track; and

one or more data tracks, wherein the servo pattern resides in the servo track, and wherein the data tracks are located defined distances from the servo track.

8. The data storage tape of claim 7, wherein the servo track is substantially magnetized in a first direction and the servo pattern is substantially magnetized in a second direction.

9. The data storage tape of claim 7, wherein the servo track is substantially randomly magnetized and the servo pattern is substantially magnetized in a common direction.

10. A method comprising:

detecting a servo signal measured from a magnetically recorded servo mark that extends across a magnetic tape in a cross-tape direction, wherein a width of the magnetically recorded servo mark defined in a down-tape direction is non-uniform across the tape in the cross-tape direction.

11. The method of claim 10, further comprising:

measuring an amplitude of the servo signal wherein the amplitude of the servo signal varies across the magnetic tape;

generating a position error signal based on the amplitude of the servo signal; and

adjusting positioning of one or more heads relative to the magnetic tape based on the position error signal.

12. The method of claim 10, further comprising:

measuring a time between detection of a leading and a trailing edge of the servo signal;

generating a position error signal based on the time; and

adjusting positioning of one or more heads relative to the magnetic tape based on the position error signal.

13. A servo head comprising a write gap that corresponds to a servo mark to be recorded in a magnetic medium, wherein a width of the write gap is non-uniform.

14. The servo head of claim 13, wherein the write gap has a trapezoidal shape and wherein the trapezoidal shape has exactly two parallel sides that correspond to top and bottom sides of the write gap.

15. The servo head of claim 13, wherein a length of the write gap is less than approximately 50 micrometers, wherein the width of the write gap varies from greater than approximately 6 micrometers to less than approximately 4 micrometers.

16. The servo head of claim 13, wherein a magnetic field strength across the write gap is non-uniform as a function of the width of the gap.

17. The servo head of claim 13, further comprising a second write gap defining a uniform width.

18. The servo head of claim 13, wherein the write gap is a first write gap, the servo head further comprising:

a second write gap defining a substantially constant width of X; and

a third write gap defining a substantially constant width of Y.

19. The servo head of claim 18, wherein the width of the first write gap varies from X to Y.