Interferometric Distance Meter Using a Frequency-Modulated Laser Diode

  • U. Minoni
  • G. Scotti
  • F. Docchio


Non-contact, non-incremental, and highly accurate distance measurements over extended ranges are required by a number of industrial applications where compact and robust measuring devices suitable for in-field usage are needed1. Frequency-modulated continuous-wave interferometry (FMCW) can be successfully used for developing non-incremental distance meters. In order to implement a reliable and compact measuring device, the use of laser diodes has been investigated2,3,4. These devices are very appealing due to their compactness, low-cost and ease of modulation. The main limitation to laser diode usage arises from the coherence length of such sources: those available with an extended coherence length are very expensive while the low-cost devices have a short and non-specified coherence. The extension of the coherence length of a laser diode can be obtained by a suitable optical feedback6. In this work, we present a distance measuring device based on both the use of a low-cost laser diode and a suitable optical feedback enabling the system to perform distance measurements over a range greater than 1 m. The main advantages of the proposed system are (i) high accuracy combined with an extended measuring range, (ii) simple optical layout, and (iii) compactness.


Laser Diode Phase Noise Beat Frequency Target Distance Optical Feedback 
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  1. 1.
    F. Docchio, U. Minoni, G. Sansoni, and E. Gelmini, Electrooptical systems and techniques for dimensional measurements for industry, in: Laser Applications for Mechanical Industry, S. Martellucci, A.N. Chester, and A.M. Scheggi, ed., Kluwer Academic Publishers, The Netherlands (1993).Google Scholar
  2. 2.
    G. Economou, R. C. Youngquist, and D. E. N. Davies, Limitations and noise in interferometric systems using frequency ramped single-mode diode lasers, J. Lightwave. Technol. LT-4:1601 (1986).CrossRefGoogle Scholar
  3. 3.
    T. Kubota, M. Nara, and T. Yoshino, Interferometer for measuring displacement and distance, Opt. Lett. 12:310(1987).CrossRefGoogle Scholar
  4. 4.
    A. Dieckmann and M. C. Amann, Phase noise limited accuracy of distance measurements in a frequency-modulated continous-wave LID AR with a tunable twin-guide laser diode, Opt. Eng. 34: 896 (1995).CrossRefGoogle Scholar
  5. 5.
    A. Destrez, Z. Toffano, I. Joindot, C. Birocheau, and L. Hassine, Measurement of spectral characteristics of semiconductor laser diodes-effect of injected current modulation and optical feddback, IEEE Trans. Instrum. Meas. 42: 304 (1993).CrossRefGoogle Scholar
  6. 6.
    U. Minoni, G. Scotti, and F. Docchio, Wide range distance meter based on frequency modulation of a Nd:YAG laser” Opt. Eng. 35 (1996).Google Scholar

Copyright information

© Springer Science+Business Media New York 1997

Authors and Affiliations

  • U. Minoni
    • 1
  • G. Scotti
    • 1
  • F. Docchio
    • 1
  1. 1.Dipartimento di Elettronica per l’Automazione, Facoltà di IngegneriaUniversità degli Studi di BresciaBresciaItaly

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