Abstract

Absolute optical ranging has been demonstrated by wavelength-multiplexed interferometry with a range resolution of 200 nm, well below the single-wavelength ambiguity. Two current- and temperature-tunable GaAlAs laser diodes (850 nm) provide an equivalent wavelength below 100 μm and a resolution of less than 200 nm. The achievement of such resolution provides the means for combining single- and multiple-wavelength interferometric measurements to achieve unambiguous distance measurement with nanometer resolution. The ranging system is also used to profile unambiguously an integrated circuit structure with a 2.5-μm surface topography.

© 1989 Optical Society of America

Full Article  |  PDF Article

References

  • View by:
  • |
  • |
  • |

  1. J. C. Wyant, Appl. Opt. 10, 2113 (1971).
    [CrossRef] [PubMed]
  2. C. Polhemus, Appl. Opt. 12, 2071 (1973).
    [CrossRef] [PubMed]
  3. C. C. Williams, H. K. Wickramasinghe, J. Appl. Phys. 60, 1900 (1986).
    [CrossRef]
  4. H. Kikuta, K. Iwata, R. Nagata, Appl. Opt. 25, 2976 (1986).
    [CrossRef] [PubMed]

1986 (2)

C. C. Williams, H. K. Wickramasinghe, J. Appl. Phys. 60, 1900 (1986).
[CrossRef]

H. Kikuta, K. Iwata, R. Nagata, Appl. Opt. 25, 2976 (1986).
[CrossRef] [PubMed]

1973 (1)

1971 (1)

Cited By

OSA participates in CrossRef's Cited-By Linking service. Citing articles from OSA journals and other participating publishers are listed here.

Alert me when this article is cited.


Figures (4)

Fig. 1
Fig. 1

Wavelength-multiplexed interferometer system. Two discrete wavelengths are temporally multiplexed into a single-mode optical fiber. The fiber output is collimated and directed into the heterodyne interferometer operating at 80 MHz. The heterodyne signal is sent to a FM demodulator, where the 80-MHz carrier is demodulated, producing an analog output proportional to the measured range. A translation stage provides the means for moving one of the interferometer mirrors. BS, beam splitter; AMP, amplifier; QWP, quarter-wave plate.

Fig. 2
Fig. 2

Output of the optical ranger as one interferometer mirror is translated approximately 400 μm parallel to the ranging beam. The ambiguity length for this wavelength pair is 70 μm.

Fig. 3
Fig. 3

Output of the optical ranger as the ranging mirror is translated in 1-μm steps at 10-sec intervals. The equivalent wavelength for this data is 42 μm.

Fig. 4
Fig. 4

Absolute optical range profile of a small portion of a passivated integrated circuit as it is laterally scanned across the ranging beam at a 10-Hz rate. The upper two traces are taken at two different range positions, differing by 3 μm.

Equations (1)

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

λ eq = λ 1 λ 2 λ 1 λ 2 .

Metrics