Self-mixing Speckle Research Articles

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

In this paper, a novel method for simultaneous measurement of rotation speed and vibration based on self-mixing speckle interference (SMSI) has been demonstrated. In view of the autocorrelation characteristic of SMSI, the time delay of laser incident during one rotation period is determined, and the rotation speed of the object is calculated according to the mathematical relationship. At the same time, the signal square-wave conversion and the global maximum fringe-counting method are proposed to measure the vibration displacement subject to the rotation. The theory and signal processing means are introduced in detail, and a series of experiments employing computer disk at different positions with various rotation speeds indicate that the proposed method achieves a simple, efficient, and accurate multi-parameter measurement.

Rotation speed measurement based on self-mixing speckle autocorrelation spectrum

A novel method of rotation speed measurement based on self-mixing speckle Autocorrelation Spectrum is presented. In this paper, Fabry–Perot cavity is used to analyze the self-mixing speckle theory. The Doppler frequency shift of the self-mixing speckle signal can be obtained by Autocorrelation Spectrum. Experimental results show that rotation speed can be measured by this means, with the error less than 2%.

Rotation speed measurement based on self-mixing speckle interference

Abstract A novel method to measure rotation speed on the basis of self-mixing speckle interference (SMSI) is proposed. The autocorrelation property of SMSI is used to determine the time delay combined with the circumference of one rotation period. In this way, the rotation speed can be measured. The proposed method is easy to implement, and it can reduce the limitation imposed by sampling rates on rotation speed range.

Measurement of rotation speed based on double-beam self-mixing speckle interference.

A rotation speed measurement based on double-beam self-mixing speckle interference is presented. The self-mixing speckle signal is analyzed by a cross-correlation algorithm. The experimental results show that, compared with the Doppler frequency shift method, the proposed method can measure high speed at a low sampling rate.

Real Time Velocity Measurement with All-fiber Self-mixing Speckle System

A novel method for real time velocity measurement is proposed. All-fiber laser measurement system is built by an erbium-doped fiber amplifier (EDFA). The measuring principle is based on laser self-mixing speckle, modulations of laser output caused by the optical feedback from an outer moving object. The generation of speckle signal is theoretically analyzed and experimentally obtained. A Labview programme is developed for waveform acquisition, noise reduction and numeric calculation. The signal processing shows a linear relationship between the energy density of speckle signal and the velocity of the moving object. In the experiments of real time velocity measurement by a rotating aluminum plate, we obtained measurement error less than 4.1% in the range of velocity from 234 to 508 mm/s. The study indicates that the all-fiber self-mixing speckle system can be applied in remote velocity sensing and measurement.

环形光纤激光器自混合散斑自相关测速的研究

环形光纤激光器自混合散斑自相关测速的研究

Autocorrelation of self-mixing speckle in an EDFR laser and velocity measurement

Autocorrelation analysis for a velocity measurement based self-mixing speckle in an erbium-doped fiber ring (EDFR) laser is presented. The expression for the velocity measurement is deduced. Theoretical analysis reveals that the velocity of a random surface is inversely proportional to the autocorrelation time of the self-mixing signal produced in the EDFR laser. In experiments, a linear fit between the velocity and the reciprocal of autocorrelation time (autocorrelation frequency) is obtained for velocity measurement. In a range of velocities from 100 mm/s to 350 mm/s, the measurement errors are evaluated to be less than 5%. The signal length, the measurement distance, and the pump power are experimentally studied for gaining knowledge of the influence on the velocity measurement.

环形掺铒光纤激光器自混合散斑及动态目标距离测量

A new method of dynamic target distance measurement based on self-mixing speckle in an erbium-doped fiber-optic ring laser is studied. The model of self-mixing speckle measurement system is presented, and the theoretical analysis of the production of self-mixing speckle signal is also given. Through the experiments, the dynamic speckle signal is obtained. The spectrum energy density analysis is applied to the dynamic speckle signals, and a linear relationship between the spectrum energy density and the detection distance is obtained. The result shows that highly precise distance dynamic measurements can be performed by using self-mixing speckle and fiber laser.

环形掺铒光纤激光器自混合散斑及动态目标距离测量

环形掺铒光纤激光器自混合散斑及动态目标距离测量

Fractal analysis of self-mixing speckle signal in velocity sensing

A new method based on fractal theory is proposed to analyze velocity sensing. The waveform of a self-mixing speckle signal is processed as a pattern of a fractal. Fractal boxes are defined as a set of grids used to divide the fractal pattern, and box-counting (BC) is introduced to characterize the statistical property of a speckle signal. A group of simulated speckle signals are analyzed by calculating the BCs corresponding to different velocities of the object. A linear dependence between the BCs of speckle signals and velocities is obtained, the result of which is validated by the analysis of a group of signals obtained from experiments. The performance of the fractal analysis is compared with those of the previous analysis methods. Better linearity and higher measurement sensitivity of the fractal analysis are indicated. The experimental result shows that the fractal method can be used as a valid analysis tool for the self-mixing speckle signal in velocity sensing.

Self-Mixing Speckle in an Erbium-Doped Fiber Ring Laser and Its Application to Velocity Sensing

In this letter, a new study of self-mixing speckle in an erbium-doped fiber ring (EDFR) laser and its application to velocity sensing is presented. We have experimentally built a fiber laser based on a ring cavity by using a packaged erbium-doped fiber amplifier and applied it to the self-mixing speckle experiments. We have also given theoretical analysis of the model of self-mixing speckle in the EDFR laser and the variation of the output power of the laser is deduced. The speckle signal has been statistically analyzed and found submitting to Gaussian distribution. For its utility to velocity sensing, the speckle signals at different velocities are processed through calculating the number of box by the fractal theory. A linear relationship between the number of box and velocity is obtained. The experimental result shows that the self-mixing speckle signal in EDFR laser can be used in velocity sensing.

Self-mixing speckle interference in DFB lasers

Theoretical analysis and experimental results of self-mixing speckle interference in a distributed feedback (DFB) laser are presented in this paper. Self-mixing speckle interference occurs when external optical feedback comes from a moving rough surface. Dynamic output variations in the DFB laser as well as their probability density functions (PDFs) are analyzed on the basis of speckle theory and self-mixing interference in the DFB laser. Numeric simulations and experiments are in agreement with each other. The both results show that self-mixing speckle interference in DFB laser can be used to measure velocity of target.

Statistics of the self-mixing speckle interference in a laser diode and its application to the measurement of flow velocity

The statistical analysis of self-mixing speckles interference using Fabry–Perot cavity is described based on the theory of the speckle and the self-mixing interference in a laser diode. Speckle signal processing based on Fourier transform is presented in this paper. The linear dependence between the spectrum mean frequency and velocity of solution is given by simulation and proved by experiment. The experimental results show that this speckle signal processing can be used to measure velocity of target.

A speckle velocimeter using a semiconductor laser with external opticalfeedback from a moving surface: effects of system parameters on thereproducibility and accuracy of measurements

A speckle velocimeter exploiting the effects of external opticalfeedback in a semiconductor laser is analysed. The laser diode is used both asthe light source and as the detector making the system self-detecting andself-aligning with a single optical axis. The velocimeter employs anautocorrelation method to analyse the detected self-mixing speckle signal. Thelinear relation between the velocity and the reciprocal of the autocorrelationtime of fluctuations in the amplitude of the speckle signal allows thedetermination of the velocity. Effects of various parameters of themeasurement system are analysed and the dependences of the reproducibility andaccuracy of the measurements on these parameters are discussed in order toachieve optimization of the system. The optimized system has a measurementerror of less than 1.4% within the range of calibration velocities and lessthan 2.7% outside this range.

Noninvasive blood flow measurement using speckle signals from a self-mixing laser diode: <italic>in vitro</italic> and <italic>in vivo</italic> experiments

A semiconductor laser speckle velocimeter that uses the self- mixing effect is studied for noninvasive relative blood flow measure- ments. The random modulation of intensity and spectra of the laser di- ode caused by the backcoupling of the scattered light from the red blood cells into the laser cavity is detected as a speckle signal with a photodi- ode inside the laser package. The autocorrelation of this self-mixing speckle signal gives information on the flow velocity of the blood. The proposed method is elucidated with in vitro and in vivo experiments. The results of these measurements are given together with a discussion of dependence of speckle signal of a self-mixing laser diode (SMLD) on various parameters such as velocity, hematocrit level of blood, and back- ground reflectance of blood suspension. © 2000 Society of Photo-Optical Instru- mentation Engineers. (S0091-3286(00)01009-6)