Obstacles in self-mixing (SM) based displacement sensing are time-consuming estimation of parameters such as an optical feedback factor and a linewidth enhancement factor, and the complex algorithm of displacement retrieval.
There have been presented fringe counting (FM) method and consecutive samples based unwrapping (CSU) method to avoid such complexities.
However, the FC method has very low resolution and the CSU method requires normalization of SM signals (SMSs), which is very complicated and even impossible when SMSs are affected by a speckle noise.
Kim Chol Hyon, a researcher at the Faculty of Physical Engineering, has proposed a new method of displacement reconstruction with high resolution, which does not need any complex processes such as parameter estimation or normalization. In addition, the method can be applied to all feedback regimes and work well even when SMSs are subject to a speckle noise.
He has presented a direct simple method of reconstructing the displacement of the target from self-mixing signals based on the velocity of the target for a weak feedback regime. Also, he has reported a simple method of displacement retrieval for moderate and strong regimes.
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