Absolute distance measurement using the frequency comb of a femtosecond laser

We describe a multi-wavelength interferometer that performs absolute distance measurements by exploiting the frequency comb of a femtosecond pulse laser as the precision wavelength ruler. An external-cavity laser diode is locked to the frequency comb and used as the tunable light source producing multiple wavelengths in discrete hopping and continuous scanning modes. This method enables high speed absolute distance metrology for industrial applications with improved measurement precision directly traceable to the Rb clock of an rf time standard.