Doppler-enhanced displacement measurement method based on scanning reference gratings

To overcome the limitations of conventional grating interferometry, which are induced by highly susceptible to environmental noise such as mechanical vibrations, airflow fluctuations, and laser wavelength drift, this paper proposes a Doppler-enhanced displacement measurement method based on scanning reference gratings (SRG). The interference between the holographic light field and the reference grating generates Moiré fringes that serve as a highly-stable carrier for displacement extraction. By introducing controlled Doppler motion into the SRG process, the detected signal undergoes period and phase modulation provide sub-nanometer repeatability in optical-period measurement, enabling the reliable identification of minute displacements. Experimental results demonstrate that the proposed method effectively exploits the intrinsic sub-nanometer measurement capability of the SRG technique. By employing continuous relative motion and temporal averaging, the impact of random vibrations and airflow-induced disturbances is substantially suppressed, thereby establishing what we believe to be a new measurement strategy for high-precision optical displacement measurement.