Dynamic test glide head calibration using laser adjustment
View Patent ↗Methods and apparatus for the calibration and use of test glide head gimbal assemblies are disclosed. Calibration is performed by pulse laser adjustment of the flexure mounted to the glide head, while the head is flying above a media test disk having asperities of known dimensions. The calibration process normalizes the fly heights of glide heads used to measure defects on both upper and lower surfaces of disk drive media, allowing upper and lower surfaces to be scanned simultaneously.
1. A method for calibrating a test glide head assembly comprising:
rotating a media test disk at a first rotation rate, said media test disk having an upper surface and a lower surface, said upper surface having a first array of asperities extending above said upper surface, said lower surface having a second array of asperities extending above said lower surface;
locating a test glide head assembly over said media test disk, said test glide head assembly having an upper test glide head positioned over said first array of asperities, said test glide head assembly having a lower test glide head positioned over said second array of asperities;
adjusting a gram loading of an upper test glide head gimbal assembly to provide contact of said upper test glide head with said first array of asperities, while said media test disk is rotating at said first rotation rate, by applying laser radiation to a first portion of said upper test glide head gimbal assembly; and,
adjusting a gram loading of a lower test glide head gimbal assembly to provide contact of said lower test glide head with said second array of asperities, while said media test disk is rotating at said first rotation rate, by applying laser radiation to a first portion of said lower test glide head gimbal assembly.
2. The method as recited in claim 1 , further comprising:
rotating said media test disk at a second rotation rate, subsequent to locating said test glide assembly over said media disk, to provide contact of said upper test glide head with said first array of asperities;
adjusting said gram loading of said lower test glide head gimbal assembly to provide contact of said lower test glide head with said second array of asperities, while said media test disk is rotating at said second rotation rate, by applying laser radiation to said first portion of said lower test glide head gimbal assembly.
3. The method as recited in claim 1 , further comprising:
rotating said media test disk at a second rotation rate, subsequent to locating said test glide assembly over said media disk, to provide contact of said lower test glide head with said second array of asperities;
adjusting said gram loading of said upper test glide head gimbal assembly to provide contact of said upper test glide head with said first array of asperities, while said media test disk is rotating at said second rotation rate, by applying laser radiation to said first portion of said upper test glide head gimbal assembly.
4. The method as recited in claim 1 , further comprising:
producing a first signal from said upper test glide head in response to contact of said upper test glide head with said first array of asperities;
adjusting a pitch angle of said upper test glide head, while said media test disk is rotating at said first rotation rate, by applying laser radiation to a second portion of said upper test glide head gimbal assembly, in response to an analysis of said first signal;
producing a second signal from said lower test glide head in response to contact of said lower test glide head with said second array of asperities; and,
adjusting a pitch angle of said lower test glide head, while said media test disk is rotating at said first rotation rate, by applying laser radiation to a second portion of said lower test glide head gimbal assembly, in response to an analysis of said second signal.
5. The method as recited in claim 4 , wherein said pitch angle of said upper test glide head is increased in response to large signal levels produced during onset of contact of said upper test glide head with said first array of asperities.
6. The method as recited in claim 4 , wherein said pitch angle of said lower test glide head is increased in response to large signal levels produced during onset of contact of said lower test glide head with said second array of asperities.
7. The method as recited in claim 4 , wherein said pitch angle of said upper test glide head is decreased in response to a high degree of modulation of said first signal, produced during contact of said upper test glide head with said first array of asperities.
8. The method as recited in claim 4 , wherein said pitch angle of said lower test glide head is decreased in response to a high degree of modulation of said second signal, produced during contact of said lower test glide head with said second array of asperities.
9. The method as recited in claim 1 , further comprising:
scanning said upper test glide head over said first array of asperities to determine a first roll angle of said upper test glide head;
scanning said lower test glide head over said second array of asperities to determine a second roll angle of said lower test glide head;
minimizing said first roll angle, while said media test disk is rotating at said first rotation rate, by applying laser radiation to a third portion of said upper test glide head gimbal assembly; and,
minimizing said second roll angle, while said media test disk is rotating at said first rotation rate, by applying laser radiation to a third portion of said lower test glide head gimbal assembly.
10. A method for calibrating a test glide head assembly comprising:
rotating a media test disk at a first rotation rate, said media test disk having an upper surface, said upper surface having an array of asperities extending above said upper surface;
locating a test glide head assembly over said media test disk, said test glide head assembly having an upper test glide head positioned over said array of asperities;
adjusting a gram loading of an upper test glide head gimbal assembly to provide contact of said upper test glide head with said array of asperities, while said media test disk is rotating at said first rotation rate, by applying laser radiation to a first portion of said upper test glide head gimbal assembly;
inverting said media test disk so that said array of asperities is located on a lower surface of said media test disk, and locating said test glide head assembly over said media test disk such that a lower test glide head is positioned over said array of asperities; and,
adjusting a gram loading of a lower test glide head gimbal assembly to provide contact of said lower test glide head with said array of asperities, while said media test disk is rotating at said first rotation rate, by applying laser radiation to a first portion of said lower test glide head gimbal assembly.
11. A method for testing production magnetic media comprising:
installing a test glide head assembly on a production media tester, said test glide head assembly comprising an upper test glide head gimbal assembly and a lower test glide head gimbal assembly;
installing a media test disk on said production media tester, said media test disk having an upper surface and a lower surface, said upper surface having a first array of asperities extending above said upper surface, said lower surface having a second array of asperities extending above said lower surface;
rotating said media test disk at a first rotation rate;
locating said test glide head assembly over said media test disk, said test glide head assembly having an upper test glide head positioned over said first array of asperities, said test glide head assembly having a lower test glide head positioned over said second array of asperities;
adjusting a gram loading of said upper test glide head gimbal assembly to provide contact of said upper test glide head with said first array of asperities, while said media test disk is rotating at said first rotation rate, by applying laser radiation to a first portion of said upper test glide head gimbal assembly;
adjusting a gram loading of said lower test glide head gimbal assembly to provide contact of said lower test glide head with said second array of asperities, while said media test disk is rotating at said first rotation rate, by applying laser radiation to a first portion of said lower test glide head gimbal assembly;
installing a least one production media disk on said production media tester, said at least one production media disk having an upper surface and a lower surface; and,
simultaneously scanning said upper and said lower surfaces of said production media disk at a second rotation rate with said test glide head assembly.
12. The method as recited in claim 11 , further comprising:
rotating said media test disk at a third rotation rate, subsequent to locating said test glide assembly over said media disk, to provide contact of said upper test glide head with said first array of asperities;
adjusting said gram loading of said lower test glide head gimbal assembly to provide contact of said lower test glide head with said second array of asperities, while said media test disk is rotating at said third rotation rate, by applying laser radiation to said first portion of said lower test glide head gimbal assembly.
13. The method as recited in claim 11 , further comprising:
rotating said media test disk at a third rotation rate, subsequent to locating said test glide assembly over said media disk, to provide contact of said lower test glide head with said second array of asperities;
adjusting said gram loading of said upper test glide head gimbal assembly to provide contact of said upper test glide head with said first array of asperities, while said media test disk is rotating at said third rotation rate, by applying laser radiation to said first portion of said upper test glide head gimbal assembly.
14. The method as recited in claim 11 , further comprising:
producing a first signal from said upper test glide head in response to contact of said upper test glide head with said first array of asperities;
adjusting a pitch angle of said upper test glide head, while said media test disk is rotating at said first rotation rate, by applying laser radiation to a second portion of said upper test glide head gimbal assembly, in response to an analysis of said first signal;
producing a second signal from said lower test glide head in response to contact of said lower test glide head with said second array of asperities; and,
adjusting a pitch angle of said lower test glide head, while said media test disk is rotating at said first rotation rate, by applying laser radiation to a second portion of said lower test glide head gimbal assembly, in response to an analysis of said second signal.
15. The method as recited in claim 14 , wherein said pitch angle of said upper test glide head is increased in response to large signal levels produced during onset of contact of said upper test glide head with said first array of asperities.
16. The method as recited in claim 14 , wherein said pitch angle of said lower test glide head is increased in response to large signal levels produced during onset of contact of said lower test glide head with said second array of asperities.
17. The method as recited in claim 14 , wherein said pitch angle of said upper test glide head is decreased in response to a high degree of modulation of said first signal, produced during contact of said upper test glide head with said first array of asperities.
18. The method as recited in claim 14 , wherein said pitch angle of said lower test glide head is decreased in response to a high degree of modulation of said second signal, produced during contact of said lower test glide head with said second array of asperities.
19. The method as recited in claim 11 , further comprising:
scanning said upper test glide head over said first array of asperities to determine a first roll angle of said upper test glide head;
scanning said lower test glide head over said second array of asperities to determine a second roll angle of said lower test glide head;
minimizing said first roll angle, while said media test disk is rotating at said first rotation rate, by applying laser radiation to a third portion of said upper test glide head gimbal assembly; and,
minimizing said second roll angle, while said media test disk is rotating at said first rotation rate, by applying laser radiation to a third portion of said lower test glide head gimbal assembly.
20. The method as recited in claim 11 , wherein laser radiation is directed to said upper and said lower test glide head gimbal assemblies by fiber optic cable.