Broad Range and High Precision Self-Mixing Interferometer Based on Spectral Analysis With Multiple Reflections

In this paper, a novel self-mixing interferometer is proposed with spectral analysis by multiple reflection technique. The relationship between the vibration amplitude, the dominant frequency, and the reflection time is deduced, which indicates that the theoretical minimum measurable vibration amplitude is 0.21λ/G(N,θ) and the precision is about 0.08λ/G(N,θ). The displacement sensitivity gain G(N,θ) increases with the reflection time. Theoretical analysis results show that the proposed method for vibration measurement has the advantages of high precision and broad measurement range, especially for the measurement of amplitude much smaller than λ/2. The validity of the method is tested by several experiments with different amplitudes and reflection times. An amplitude of 75 nm has been proved to be measurable and the absolute error is 5.43 nm, which is within the theoretical error range. The proposed method plays an important role in high precision and nanoscale measurement.