Noncoaxial RDE of circular asymmetry optical vortex for rotating axis detection

We reveal the mechanism of the noncoaxial rotational Doppler effect (RDE) of an optical vortex and report its application in discriminating the orientation of the rotating axis of the rotating body. In most cases of the RDE-based measurement, the beam axis must be aligned with the rotating axis of the rotational body to observe a good signal. Once the beam axis is not coaxial with the rotating axis, the RDE frequency shift would change related to the misalignment distance, which can be called the noncoaxial RDE. Here, we take the advantage of the mis-aligned RDE augment with precise light-field modulation and successfully realize the discrimination of the ori-entation of the rotating axis relative to the illuminating beam. We clarify the principle of noncoaxial RDE and explain why the incomplete optical vortex (OV) is sensitive to the position of the rotating axis. We switch the OV field into four quadrants synchronized with sampling by the data acquisition system, and conduct Fourier trans-formation of the signals. Combined with the fitting algorithm, the orientation of the rotating axis can be rec-ognized directly. This method may find applications for the noncontact detection of rotating bodies in both industrial and astronomical scenarios.(c) 2022 Chinese Laser Press

Automated summary

This study reveals the mechanism of the noncoaxial rotational Doppler effect (RDE) of an optical vortex and demonstrates its application in discriminating the orientation of a rotating body. By precisely modulating the light field and using signal processing algorithms, the orientation of the rotating axis can be directly recognized.