OSA's Digital Library

Applied Optics

Applied Optics


  • Vol. 39, Iss. 4 — Feb. 1, 2000
  • pp: 578–584

Scanning laser differential-heterodyne interferometer for flying-height measurement

Bryan Kok Ann Ngoi, Krishnan Venkatakrishnan, and Bo Tan  »View Author Affiliations

Applied Optics, Vol. 39, Issue 4, pp. 578-584 (2000)

View Full Text Article

Enhanced HTML    Acrobat PDF (113 KB)

Browse Journals / Lookup Meetings

Browse by Journal and Year


Lookup Conference Papers

Close Browse Journals / Lookup Meetings

Article Tools



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

OCIS Codes
(040.2840) Detectors : Heterodyne
(120.3180) Instrumentation, measurement, and metrology : Interferometry
(120.5800) Instrumentation, measurement, and metrology : Scanners
(230.1040) Optical devices : Acousto-optical devices

Original Manuscript: June 30, 1999
Revised Manuscript: November 3, 1999
Published: February 1, 2000

Bryan Kok Ann Ngoi, Krishnan Venkatakrishnan, and Bo Tan, "Scanning laser differential-heterodyne interferometer for flying-height measurement," Appl. Opt. 39, 578-584 (2000)

Sort:  Author  |  Year  |  Journal  |  Reset  


  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).

Cited By

Alert me when this paper is cited

OSA is able to provide readers links to articles that cite this paper by participating in CrossRef's Cited-By Linking service. CrossRef includes content from more than 3000 publishers and societies. In addition to listing OSA journal articles that cite this paper, citing articles from other participating publishers will also be listed.

« Previous Article  |  Next Article »

OSA is a member of CrossRef.

CrossCheck Deposited