Laser-Based Detection of Rotation Speed with High Accuracy and High Signal-to-Noise Ratio (SNR) Based on the Rotational Doppler Effect
Z-M. Li, L-L. Chen, Y. Ren, S. Qiu, T. Liu, C. Wang and H. Wang
Measuring the rotation speed of an object based on the rotational Doppler effect (RDE) is a novel technique that has emerged in recent years. Still, most previous studies utilized the simulated pattern to replace the real rotation object, which is far from the practical applications. In this paper we investigate a laser -based method of rotation speed measurement based on the RDE by employing a real rotating metal disk in different conditions. We detect different rotational speeds ranging from 113.10 to 697.40 rad/s with superimposed optical vortices of constant topological charges 𝑙=±16. Meanwhile, related experiments are performed under the condition of different topological charges ranging from 𝑙=±12 to 𝑙=±25 at constant rotation speed of 590.68 rad/s. Typically, we employ optical vortices with different quality to explore its impact on detection accuracy and signal-to-noise ratio (SNR). We achieve good results that the relative errors are less than 0.5% and the SNRs are higher than 20 dB. Finally, we analyse the origin of error, and find purity and misalignments are the two main factors that would influence the performance of detection. Our results may be useful for high precision measurements of rotation speed in practical applications.
Keywords: He-Ne laser, rotation speed, optical vortex, rotational Doppler effect (RDE), orbital angular momentum (OAM)