The Design Of High-speed Data Processing System Of Laser Self-mixing Interference Signal Based On FPGA

Self-mixing interference effect refers to the emitted light is reflected or scattered by external object,part of the light returns to the laser, mixes with the cavity,causing the laser output frequency, power change, so called self-mixing interference.As a new measurement techniques, self-mixing interference with a non-contact, high accuracy, high-precision and other advantages has been widely used in the amount of external mechanical objects,geometric parameters of the laser and the like.Wherein,the external object extraction and phase displacement measurement are two main applications.Traditional methods for measuring the displacement of external object is usually the first collect and save experimental data, and then use MatLab mathematical software combining algorithms obtain the final displacement amount and direction of the object. The advantage of this method is that the algorithm flexible, high precision processing; The disadvantage is not high-speed real-time processing and display for interference signal.The traditional method of extracting phase object is usually combined with the use MatLab mathematical software combining algorithm to finish offline processing,which does not achieve the goal of high-speed extraction of phase information. FPGA, chip deveslopment cycle is short, high operating frequency, internal procedures in parallel operation, etc.,can be data acquisition, processing and transmission functions integrated in a single chip,so FPGA can be used to design effective real-time data processing system.In this paper,a laser self-mixing interference signal as the research object,take the advantages of FPGA high-speed digital signal acquisition and processing to design FPGA-based self-mixing laser data processing system, the paper main work is as follows:1、The comparison return home method of self-mixing interference signal is proposed to calculate micro displacement,the vibration stripes integer,fractional part and direction are calculated,and then micro-displacement is calculated.The algorithm,combining Quartus II,are implemented in Verilog HDL.Self-mixing interference signal micro-displacement measuring system based on FPGA is designed, the experimental verification and analysis is made,the experimental results show,the micro-displacement measuring system with high-speed real-time and data feedback time is 0.5s,the displacement of the measurement results relative error lower, Respectively rate is λ/20,the micro-displacement measuring system meet the needs of self-mixing interference signal high-speed accurate measurement.2、FFT phase extraction theory is analyzed and simulation of MatLab is made, The FFT algorithm,combining Quartus Ⅱ,are implemented in Verilog HDL.Self-mixing interference signal phase extraction system based on FPGA is designed,the experimental verification is made,the experimental results show,the phase extraction system with high-speed real-time and data feedback time is 0.5s,phase values obtained based on FFT with respect to the actual value of the relative phase error low,the phase extraction system meet the needs of self-mixing interference signal high-speed accurate measurement.