Comb-calibrated frequency sweeping interferometry for absolute distance and vibration measurement

We present here an absolute distance measurement system based on frequency sweeping interferometry calibrated with a frequency comb. The instantaneous frequency of the sweeping laser is calibrated at some discrete frequencies corresponding to the comb lines using a narrow bandpass filter. A large number of frequency calibration peaks have been derived in sub-measurements based on fringe counting, leading to a precision improvement by a factor of 10 in a full sweep. A precision of 75 nm for distances around 0.84 m (corresponding to 89×10^-9 in relative term) has been achieved. Also, 1.7 nm of vibration measurement in terms of RMS noise has been obtained benefiting from the dense lines of a frequency comb and the sub-measurement principle.