Proceedings PaperDiode laser and fiber optics for dual-wavelength heterodyne interferometry
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Interferometric systems in general are sensitive with the wavelength of the optical signal. For many applications this extreme sensitivity is of hindrance instead of help. Dual-wavelength interferometry employs two adjacent laser lines and X 2and uses the beat frequencybetween both signals. Thus, sensitivity and ambiguity are reduced from the optical wavelength X to a "synthetic" wavelength (formula available on paper). Dual-wavelength interferometry was previously applied by TiZiani' for surface inspection and by Dändliker et aL2 for superheterodyne range measurements. Our approach was to replace the commonly used gas lasers by semiconductor lasers (to reduce volume and weight) and to use optical fibers for the signal distribution (to be more compact and to get rid of alignment and optical cross-talk problems). A demonstration model for precise ranging to 10 m distant, reflective and rough targets was built and tested.