A dual resolution noncontact vibration and displacement sensor based upon a two wavelength source

An optical configuration, utilizing a two wavelength source is presented. Its use as both a normal heterodyne-interferometric sensor yielding nanometer resolution, and as a subcarrier system with a much enhanced unambiguous range, but reduced resolution, are discussed. A major attribute of this system is that heterodyne signal processing has been achieved without the use of a frequency or phase shifter. Preliminary results indicate the resolution of the first configuration is comparable to that achievable in interferometric systems, while the latter shows a displacement resolution of greater than 1 mm, and vibration amplitude resolution of greater than 10 μm, over a 22-cm dynamic range.