Sinusoidal frequency sweeping interferometric absolute distance measurement apparatus and method with dynamic offset frequency locking

Abstract

A reference laser beam locked to a femtosecond optical frequency comb is modulated through a high frequency electro-optic phase modulator, and laser sidebands with equal intervals are generated. Beat frequency is performed on the sixth-order sideband and the frequency sweeping laser beam, a beat signal and a frequency sweeping signal source are down-mixed to generate a difference frequency signal, and the difference frequency signal is locked to a reference clock through a digital phase detector and a PID controller. The frequency sweeping laser beam is locked to reference laser beam with a dynamic offset frequency under the closed loop control, and sinusoidal frequency sweeping is simultaneously performed together with the frequency sweeping signal source. The locked laser beam is used for absolute distance measurement, and a distance to be measured is obtained according to the synthetic wavelength transition theory.