Speckle affected fringe detection based on three envelope extraction for self-mixing displacement measurement

Micro Particle Sizing Using Hilbert Transform Time Domain Signal Analysis Method in Self-Mixing Interferometry

“…Such a method could represent a signal in its analytical form by performing a 90 • phase shift of the original signal over the orthogonal plane without modifying the amplitude, and the phase information is independent of the signal amplitude variations [24]. So far, HT has presented a good performance on SMI signals, as proven in many reports [25][26][27]. Herein, we employed the HT to unwrap the simultaneous external phase φ(t) and extract the fringe number correctly.…”

Vibration Measurement Based on the Local Maximum Detection Algorithm for Laser Self-Mixing Interferometry

“…Laser self-mixing interference theory was first presented by Lang and Kobayashi in 1980 [21]; the well-known equation is also named after them. Many researchers have studied Lang-Kobayashi theory [1], [2], [22]. The vibration of the external target induces the modulation of the length of the external cavity, which leads to SMI.…”

“…The basic theories of the self-mixing interference effect can be explained by two Fabry-Pérot cavities, as shown in Fig. 1 [22], in which r 1 and r 2 denote the amplitude reflectivity of LD facets, r 3 is the amplitude reflectivity of the external target, l is the length of the laser cavity and L represents the length of the external cavity. The output power signal is detected by a PD.…”

“…The LMPs of the SMI are acquired. However, the detection of LMPs does not contain directivity [22]. We propose the window function method based on the inverse point to obtain the right direction for the LMPs.…”

“…The correct window function is based on adopting the median of the derivative of the SMI signal [20], [22]. Fig.…”