Phase-Locked Synthetic Wavelength Interferometer Using a Femtosecond Laser for Absolute Distance Measurement without Cyclic Error

We present a phase-locked synthetic wavelength interferometer that enables a complete elimination of cyclic errors in absolute distance measurements. With this method, the phase difference between the reference and measurement paths is fed back into a phase lock-in system, which is then used to control the synthetic wavelength and set the phase difference to zero using an external cavity acousto-optic modulator. We validated the cyclic error removal of the proposed phase-locked method by comparing it with the conventional phase-measuring method of the synthetic wavelength interferometer. By analyzing the locked error signal, we achieved a precision of 0.6 mrad in phase without any observed cyclic errors.

Automated summary

We propose a phase-locked synthetic wavelength interferometer that eliminates cyclic errors in absolute distance measurements. The phase difference between the reference and measurement paths is fed back into a phase lock-in system to control the synthetic wavelength and achieve zero phase difference. By comparing with the conventional phase-measuring method, we validate the cyclic error removal of the proposed method. With a precision of 0.6 mrad in phase and no observed cyclic errors, the locked error signal analysis confirms the effectiveness of the phase-locked method.