High-precision micro-displacement measurement method based on alternately oscillating optoelectronic oscillators

We propose a high-precision micro-displacement measurement method based on alternately oscillating optoelectronic oscillators (OEOs). This method uses a reference loop to compensate for the change in the measuring loop length except for the displacement to be measured. Therefore, self-calibration is realized without using a phase-locked loop to control the loop length, greatly simplifying the system. The measurement range is 20 mm, and the measurement precision is <300 nm, which is limited by the incomplete consistency between the reference and the measuring loops, with the exception of the displacement to be measured and environmental disturbances resulting from the spatial optical path.