Improved transition detection algorithm for a self-mixing displacement sensor

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

“…For C > 4.6, the SMI fringes become sawtooth-like and exhibit hysteresis. For the moderate feedback regime, the piecewise transition detection algorithm was proposed on the basis of SMI signal differentials [9], [18], [25]. However, identifying the direction of the target directly from the SMI signal in the weak feedback regime is difficult because the signals are nearly sinusoidal.…”

“…where λ 0 represents the initial wavelength of the laser and λ F represents the wavelength with optical feedback. Moreover, given the weak feedback regime [9] φ 0 (t) ≈ φ F (t), and according to (3), the external target vibration expression can be written as…”

“…The output SMI power is detected by a built-in monitor photodiode (PD). The SMI technique is used in several fields of research in applications such as measuring absolute distance [7], [8]; displacement [9]; vibration [10], [11]; and velocity [12], [13]; and imaging [14]; and laser parameter measurement [15], [16] due to its compactness, self-alignment, and low cost.…”

“…the measurement accuracy beyond a half-wavelength, Jiang et al proposed an improved transition detection algorithm that can differentiate between different SMI feedback levels [9]. However, false transitions could lead to measurement error.…”

Single Channel Instrument for Simultaneous Rotation Speed and Vibration Measurement Based on Self-Mixing Speckle Interference

“…Self-mixing interference (SMI) is a phenomenon in which part of the emitted light is reflected or scattered by the external object and re-enters the laser cavity, resulting in fluctuations in the power and frequency of the laser. Owing to its advantages of compactness, intrinsic simplicity, and self-alignment, SMI has become a new kind of sensing technology and is extensively used in measuring displacement [1][2][3], velocity [4,5], distance [6,7], vibrations [8][9][10], 3D imaging, biomedical sensing [11] and other occasions [12]. In 1999, K.Özdemir firstly proposed a method for measuring velocity and length of moving surfaces simultaneously by a speckle velocimeter [13].…”