Abstract

With conventional optical interferometry flying-height testing, a stationary measurement beam and a two-axis moving stage are used to measure slider–disk spacing at different points on the slider. Pitch angle or roll angle is calculated on the basis of the measurement results. We report on a scanning differential-heterodyne interferometer, which measures the continuous flying-height variation along the edge of a slider with two continuously scanning laser beams. Pitch angle or roll angle can be obtained directly from the scanning measurement. The system can also measure points individually to obtain the absolute flying height at different locations on the slider. Experiments were performed to demonstrate the concept of scanning measurement. The flying-height variation along the slider edge was measured by continuous scan and by point-to-point moving. The measurement results from continuous scan coincided with those of conventional methods.

© 2000 Optical Society of America

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References

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  1. Y. Li, A. Menon, “Flying height measurement metrology for ultra-low spacing in rigid magnetic recording,” IEEE Trans. Magn. 32, 129–134 (1996).
    [CrossRef]
  2. T. Ohkubo, J. Kishigami, “Accurate measurement of gas-lubricated slider bearing separation using visible laser interferometry,” J Tribol. 110, 148–155 (1988).
    [CrossRef]
  3. P. de Groot, L. Deck, J. Soobitsky, J. Biegen, “Polarization interferometer for measuring the flying height of magnetic read–write heads,” Opt. Lett. 21, 441–443 (1996).
    [CrossRef] [PubMed]
  4. R. J. Davidson, “Application of heterodyne interferometry to disc drive technology,” in Manufacturing Applications of Lasers, P. K. Cheo, ed., Proc. SPIE621, 126–128 (1986).
    [CrossRef]
  5. L.-Y. Zhu, K. F. Hallamasek, D. B. Bogy, “Measurement of head/disk spacing with a laser interferometer,” IEEE Trans. Magn. 24, 2739–2741 (1988).
    [CrossRef]
  6. D. Henze, P. Mui, G. Clifford, R. J. Davidson, “Multi-channel interferometric measurements of slider flying height and pitch,” IEEE Trans. Magn. 25, 3710–3712 (1989).
    [CrossRef]
  7. T. C. McMillan, F. E. Talke, “Ultra low flying height measurements using monochromatic and phase demodulated laser interferometry,” IEEE Trans. Magn. 30, 4173–4175 (1994).
    [CrossRef]
  8. D. H. Veillard, “Real-time tracking of the head-disk separation using laser heterodyne interferometry. 1. Instrumentation,” IEEE Trans. Magn. 29, 3909–3911 (1993).
    [CrossRef]
  9. T. C. McMillan, F. E. Talke, “An investigation of the ‘take-off’ characteristic of tri-pad slider using phase demodulated laser interferometry,” IEEE Trans. Magn. 33, 3133–3135 (1997).
    [CrossRef]
  10. B. K. A. Ngoi, K. Venkatakrishnan, “Noncontact acousto optic scanning laser vibrometer,” U.S. Patent Application (29December1998).
  11. B. K. A. Ngoi, K. Venkatakrishnan, “Techniques to eliminate error induced due to AOM vibration in heterodyne interferometry,” Opt. Eng. (to be published).

1997

T. C. McMillan, F. E. Talke, “An investigation of the ‘take-off’ characteristic of tri-pad slider using phase demodulated laser interferometry,” IEEE Trans. Magn. 33, 3133–3135 (1997).
[CrossRef]

1996

Y. Li, A. Menon, “Flying height measurement metrology for ultra-low spacing in rigid magnetic recording,” IEEE Trans. Magn. 32, 129–134 (1996).
[CrossRef]

P. de Groot, L. Deck, J. Soobitsky, J. Biegen, “Polarization interferometer for measuring the flying height of magnetic read–write heads,” Opt. Lett. 21, 441–443 (1996).
[CrossRef] [PubMed]

1994

T. C. McMillan, F. E. Talke, “Ultra low flying height measurements using monochromatic and phase demodulated laser interferometry,” IEEE Trans. Magn. 30, 4173–4175 (1994).
[CrossRef]

1993

D. H. Veillard, “Real-time tracking of the head-disk separation using laser heterodyne interferometry. 1. Instrumentation,” IEEE Trans. Magn. 29, 3909–3911 (1993).
[CrossRef]

1989

D. Henze, P. Mui, G. Clifford, R. J. Davidson, “Multi-channel interferometric measurements of slider flying height and pitch,” IEEE Trans. Magn. 25, 3710–3712 (1989).
[CrossRef]

1988

L.-Y. Zhu, K. F. Hallamasek, D. B. Bogy, “Measurement of head/disk spacing with a laser interferometer,” IEEE Trans. Magn. 24, 2739–2741 (1988).
[CrossRef]

T. Ohkubo, J. Kishigami, “Accurate measurement of gas-lubricated slider bearing separation using visible laser interferometry,” J Tribol. 110, 148–155 (1988).
[CrossRef]

Biegen, J.

Bogy, D. B.

L.-Y. Zhu, K. F. Hallamasek, D. B. Bogy, “Measurement of head/disk spacing with a laser interferometer,” IEEE Trans. Magn. 24, 2739–2741 (1988).
[CrossRef]

Clifford, G.

D. Henze, P. Mui, G. Clifford, R. J. Davidson, “Multi-channel interferometric measurements of slider flying height and pitch,” IEEE Trans. Magn. 25, 3710–3712 (1989).
[CrossRef]

Davidson, R. J.

D. Henze, P. Mui, G. Clifford, R. J. Davidson, “Multi-channel interferometric measurements of slider flying height and pitch,” IEEE Trans. Magn. 25, 3710–3712 (1989).
[CrossRef]

R. J. Davidson, “Application of heterodyne interferometry to disc drive technology,” in Manufacturing Applications of Lasers, P. K. Cheo, ed., Proc. SPIE621, 126–128 (1986).
[CrossRef]

de Groot, P.

Deck, L.

Hallamasek, K. F.

L.-Y. Zhu, K. F. Hallamasek, D. B. Bogy, “Measurement of head/disk spacing with a laser interferometer,” IEEE Trans. Magn. 24, 2739–2741 (1988).
[CrossRef]

Henze, D.

D. Henze, P. Mui, G. Clifford, R. J. Davidson, “Multi-channel interferometric measurements of slider flying height and pitch,” IEEE Trans. Magn. 25, 3710–3712 (1989).
[CrossRef]

Kishigami, J.

T. Ohkubo, J. Kishigami, “Accurate measurement of gas-lubricated slider bearing separation using visible laser interferometry,” J Tribol. 110, 148–155 (1988).
[CrossRef]

Li, Y.

Y. Li, A. Menon, “Flying height measurement metrology for ultra-low spacing in rigid magnetic recording,” IEEE Trans. Magn. 32, 129–134 (1996).
[CrossRef]

McMillan, T. C.

T. C. McMillan, F. E. Talke, “An investigation of the ‘take-off’ characteristic of tri-pad slider using phase demodulated laser interferometry,” IEEE Trans. Magn. 33, 3133–3135 (1997).
[CrossRef]

T. C. McMillan, F. E. Talke, “Ultra low flying height measurements using monochromatic and phase demodulated laser interferometry,” IEEE Trans. Magn. 30, 4173–4175 (1994).
[CrossRef]

Menon, A.

Y. Li, A. Menon, “Flying height measurement metrology for ultra-low spacing in rigid magnetic recording,” IEEE Trans. Magn. 32, 129–134 (1996).
[CrossRef]

Mui, P.

D. Henze, P. Mui, G. Clifford, R. J. Davidson, “Multi-channel interferometric measurements of slider flying height and pitch,” IEEE Trans. Magn. 25, 3710–3712 (1989).
[CrossRef]

Ngoi, B. K. A.

B. K. A. Ngoi, K. Venkatakrishnan, “Noncontact acousto optic scanning laser vibrometer,” U.S. Patent Application (29December1998).

B. K. A. Ngoi, K. Venkatakrishnan, “Techniques to eliminate error induced due to AOM vibration in heterodyne interferometry,” Opt. Eng. (to be published).

Ohkubo, T.

T. Ohkubo, J. Kishigami, “Accurate measurement of gas-lubricated slider bearing separation using visible laser interferometry,” J Tribol. 110, 148–155 (1988).
[CrossRef]

Soobitsky, J.

Talke, F. E.

T. C. McMillan, F. E. Talke, “An investigation of the ‘take-off’ characteristic of tri-pad slider using phase demodulated laser interferometry,” IEEE Trans. Magn. 33, 3133–3135 (1997).
[CrossRef]

T. C. McMillan, F. E. Talke, “Ultra low flying height measurements using monochromatic and phase demodulated laser interferometry,” IEEE Trans. Magn. 30, 4173–4175 (1994).
[CrossRef]

Veillard, D. H.

D. H. Veillard, “Real-time tracking of the head-disk separation using laser heterodyne interferometry. 1. Instrumentation,” IEEE Trans. Magn. 29, 3909–3911 (1993).
[CrossRef]

Venkatakrishnan, K.

B. K. A. Ngoi, K. Venkatakrishnan, “Techniques to eliminate error induced due to AOM vibration in heterodyne interferometry,” Opt. Eng. (to be published).

B. K. A. Ngoi, K. Venkatakrishnan, “Noncontact acousto optic scanning laser vibrometer,” U.S. Patent Application (29December1998).

Zhu, L.-Y.

L.-Y. Zhu, K. F. Hallamasek, D. B. Bogy, “Measurement of head/disk spacing with a laser interferometer,” IEEE Trans. Magn. 24, 2739–2741 (1988).
[CrossRef]

IEEE Trans. Magn.

L.-Y. Zhu, K. F. Hallamasek, D. B. Bogy, “Measurement of head/disk spacing with a laser interferometer,” IEEE Trans. Magn. 24, 2739–2741 (1988).
[CrossRef]

D. Henze, P. Mui, G. Clifford, R. J. Davidson, “Multi-channel interferometric measurements of slider flying height and pitch,” IEEE Trans. Magn. 25, 3710–3712 (1989).
[CrossRef]

T. C. McMillan, F. E. Talke, “Ultra low flying height measurements using monochromatic and phase demodulated laser interferometry,” IEEE Trans. Magn. 30, 4173–4175 (1994).
[CrossRef]

D. H. Veillard, “Real-time tracking of the head-disk separation using laser heterodyne interferometry. 1. Instrumentation,” IEEE Trans. Magn. 29, 3909–3911 (1993).
[CrossRef]

T. C. McMillan, F. E. Talke, “An investigation of the ‘take-off’ characteristic of tri-pad slider using phase demodulated laser interferometry,” IEEE Trans. Magn. 33, 3133–3135 (1997).
[CrossRef]

Y. Li, A. Menon, “Flying height measurement metrology for ultra-low spacing in rigid magnetic recording,” IEEE Trans. Magn. 32, 129–134 (1996).
[CrossRef]

J Tribol.

T. Ohkubo, J. Kishigami, “Accurate measurement of gas-lubricated slider bearing separation using visible laser interferometry,” J Tribol. 110, 148–155 (1988).
[CrossRef]

Opt. Lett.

Other

R. J. Davidson, “Application of heterodyne interferometry to disc drive technology,” in Manufacturing Applications of Lasers, P. K. Cheo, ed., Proc. SPIE621, 126–128 (1986).
[CrossRef]

B. K. A. Ngoi, K. Venkatakrishnan, “Noncontact acousto optic scanning laser vibrometer,” U.S. Patent Application (29December1998).

B. K. A. Ngoi, K. Venkatakrishnan, “Techniques to eliminate error induced due to AOM vibration in heterodyne interferometry,” Opt. Eng. (to be published).

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Figures (8)

Fig. 1
Fig. 1

Flying-height measurement differential-heterodyne interferometry with scanning reference beam and measurement beam.

Fig. 2
Fig. 2

Schematic diagram for laser scanning differential-heterodyne interferometer. PD, photodetector; M, mirror; BS, beam splitter; TL, telecentric lens.

Fig. 3
Fig. 3

Working principle of telecentric lens.

Fig. 4
Fig. 4

Geometric structure of the optical system (all wave plates are omitted). PD, photodetector; M, mirror; D, distance; BS, beam splitter; TL, telecentric lens.

Fig. 5
Fig. 5

Measurement locations on the backside of the slider.

Fig. 6
Fig. 6

Flying height at location 375 µm.

Fig. 7
Fig. 7

Flying height at different locations.

Fig. 8
Fig. 8

Flying height measured by continuous scanning.

Equations (8)

Equations on this page are rendered with MathJax. Learn more.

fD=f02ν/c,
ϕ/2π=2f0/cx-x0,
xD-x0=ϕD2π-NDc2f0,
xS-x0=ϕS2π-NSc2f0,
d=xD-xS=ϕD-ϕS2π+ND-NSc2f0.
θBsin θB=λ0fa2nνa,
F=fθB,
F=f λ0fa2νa.

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