Abstract

Self-Mixing (SM) is a promising technique for sensing vibration, distance, velocity etc. To retrieve accurate metric measurements from an acquired SM signal, it is necessary to correctly detect all interferometric fringes. Traditionally, SM fringes are detected by a derivative based threshold (DBT) scheme. However, such a scheme gives correct results only for SM signals with high signal-to-noise ratio (SNR) and moderate optical feedback regime. So, in this paper, a better fringe detection method, based on Matched Filter (MF), is proposed which has provided correct SM fringe detection even in case of low SNR and weak optical feedback regime. The proposed approach has resulted in fringe detection accuracy of 100% for a low SNR SM signal belonging to the weak feedback regime.

Highlights

  • Self-mixing (SM) or optical feedback interferometry technique [1] has become an attractive area for the sensing of vibration [2] and biomedical applications [3]

  • SM fringe detection approaches such as derivative based threshold (DBT) method degrades in case of low signal to noise ratio (SNR) which lead to degraded displacement measurement results

  • It is worth-mentioning that the shown output of matched filter 2 (MF2) is inverted as it is a requirement of phase unwrapping methods [4,5,6,7]

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Summary

Introduction

Self-mixing (SM) or optical feedback interferometry technique [1] has become an attractive area for the sensing of vibration [2] and biomedical applications [3]. SM fringe detection becomes a fundamental step which is later built upon by these PUMs. Usually, simple derivative based threshold (DBT) method is sufficient to detect SM fringes [4,5]. Simple derivative based threshold (DBT) method is sufficient to detect SM fringes [4,5] Such a simple approach fails in case of either low signal to noise ratio (SNR). Other methods such as customized wavelets [8] have been previously proposed. SM fringe detection approaches such as DBT method degrades in case of low SNR which lead to degraded displacement measurement results. A new technique, based on the use of Matched Filter (MF) technique, is being proposed which has resulted in correct detection of all SM fringes belonging to a noisy SM signal with low SNR

Self-Mixing Interferometry
MF Based Fringe Detection
Results
Conclusions

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