Rotation speed measurement based on self-mixing speckle interference

A novel method to measure rotation speed on the basis of self-mixing speckle interference (SMSI) is proposed. The autocorrelation property of SMSI is used to determine the time delay combined with the circumference of one rotation period. In this way, the rotation speed can be measured. The proposed method is easy to implement, and it can reduce the limitation imposed by sampling rates on rotation speed range.