The knotty problems in displacement reconstruction based on self-mixing (SM) technique are estimation of self-mixing interferometry parameters and normalization of SM signals (SMSs) since they are all very time-consuming and based on complex algorithms. This has an unfavorable effect on the real-time and low-cost natures of an SM displacement sensor.
Kim Chol Hyon, a researcher at the Faculty of Physical Engineering, has presented a simple method of displacement retrieval with a high resolution, which does not require any parameter estimation and normalization.
According to his study, when C changes during the operation of a self-mixing sensor, a single fringe, in a strict sense, does not correspond to a half wavelength and, therefore, this causes inaccuracy in displacement reconstruction. On the basis of it, he has proposed a very simple method called fringe scaling for displacement reconstruction, which does not require any normalization of SMSs and parameter estimation. This method provides a high resolution of λ0/10 and in addition, it can be employed for all feedback regimes including weak, moderate and strong regimes.
The proposed method is based on the scaling of individual fringes in SMSs and speckle noise proof. The simplicity of the method will make a great contribution to lowering the cost of SM displacement sensors and improving their reliability and resolution.
For more information, please refer to his paper “Normalization-free displacement reconstruction method based on fringe scaling” in “Applied optics” (SCI).
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