Research On The Frequncy Modulation Non-linear Correction Of Semiconductor Lasers Based On FPGA

Linear Frequency Modulated Continuous Wave(LFMCW)is an emerging distance measurement technology,with no target,no blind spot,non-contact and other traditional means of distance does not have the advantages.Because of this,the technology can be used for some complex large-size workpiece processing and testing,while more accurate measurement,faster efficiency.Although the advantages of FM continuous wave ranging technology,but the disadvantage is that as a light source of the laser frequency of non-linear degree of distance measurement accuracy and distance resolution of a serious impact.It is necessary to study the frequency modulation nonlinear correction technique of laser only when the linearity of the laser is very high in order to obtain high ranging accuracy and ranging resolution.In this paper,the FM correction technique of DFB laser is mainly studied.Firstly,the principle of FMCW ranging is introduced,and the calculation formula of corresponding parameters is given.The influence of frequency modulation nonlinearity on distance measurement and ranging resolution is analyzed.In this paper,the nonlinear correction method of DFB laser is briefly described.Secondly,the non-linear correction method is used to determine the non-linearity of the initial large bandwidth range using the iterative correction method.The non-linearity of DFB laser is given The mathematical model,the physical meaning and the algorithm flow are designed.According to the requirement of the signal phase accuracy,the FIR filter is used to realize the iterative correction algorithm,and the iterative correction algorithm based on the secant method is designed.The basic theory of FIR filter and its implementation in FPGA are introduced.Then,the implementation scheme of iterative correction algorithm based on FPGA is introduced in detail.According to the experimental parameters,the device is selected and designed.Based on the minimum FPGA system and the corresponding external circuit;which is the key equivalent Section has been designed and its frequency response and phase-frequency corresponding verified.Finally,an FPGA-based laser frequency modulation nonlinear correction system is proposed.The experimental results show that the correction effect of the iterative algorithm has improved the frequency modulation nonlinearity of the tuned semiconductor laser,and the repetitive test has proved that the iterative correction algorithm has good And the noise and error sourcesof the calibration system are analyzed in combination with the proposed correction principle,hardware circuit and optical path structure.