Compact interferometric displacement gauge with sub-nanometer resolution and milimeter range

We report on the design and prototype realization of the gauge probe sensor for the measurement of displacement based on a laser interferometer. The measurement system incorporates a suitable laser source and interferometric phase processing system. The phase extraction (fringe counting) relies on a single-detector homodyne detection method for phase extraction that uses a harmonic optical frequency modulation of the laser beam and allows for a significantly reduced and thus compact and robust optical arrangement. The experimental verification revealed that the sensor system achieves the sub-nanometer precision and nanometer accuracy in the 10 mm measurement range.