Study On The Micro-displacement Measuring System By Laser Self-mixing Effect

Recently,it has been widely concerned about the applications of LFA?Laser force accelerometer?and LA?Laser accelerometer?.The key technique remains unfathomed in how to accurately measure the displacements of micro-spheres in LFA or flexible pendulous reeds in LA.Due to its features of non-contact,high-accuracy and traceability,the laser self-mixing interference metrology,as an emerging sensing technology,has wide applications and great potentials in many aspects,such as the measurements of displacements,velocities,angles,deformations,and so on.The thesis involves the design of a displacement measuring system with10^-8m order accuracy based on the laser self-mixing interference effects,which will be very important for displacement metrology in LFA or LA.Firstly a consistent common model of the laser self-mixing interference effect has been derived from the models of three-mirror F-P cavity and Lang-Kobayashi rate equations.Subsequently simulations are employed for phase and power equations in the common models.The principles of single-mode laser in steady-state have been analyzed detailedly in a weak feed-back mode,while the mechanism of mode transitions and phase delay are also involved in moderate feed-back mode and strong feed-back mode.Secondly the self-mixing interference signal is simulated by the general model of the self-mixing interference effect in a weak feed-back level,and the effects of different displacement parameters on the self-mixing interference signal are compared.In the condition of the linear injection current modulating laser,the displacement measurement model based on the laser self-mixing interference effect is deduced.And the all-phase FFT spectrum analysis technology is applied to measure the phase information of self-mixing interference signal.The advantages and disadvantages of all-phase FFT spectrum analysis and traditional FFT spectrum analysis are compared by simulation modeling analysis,and the abilities of suppressing spectrum leakage and maintaining phase invariance of all-phase FFT spectrum analysis are verified in the digital signal processing.Finally the observing experiments of the self-mixing effect and the displacement measuring experiment are carried out through the designed micro-displacement measuring system based on the laser self-mixing effect.The experimental results of displacement measurement are in good agreement with the simulation results.The system can realize micro-displacement measurement with10^-8m precision,and the main sources of measuring error are analyzed.Besides,the temperature control experiments of VCSEL are carried out by using the self-developed drive circuit.The precision of temperature control can reach?0.08?C,which is beneficial to realize the integration and miniaturization development of the micro-displacement measuring system based on the laser self-mixing effect.