Output Power Of Laser Frequency Modulation Ranging Control Technology Research Based On Variable Optical Attenuator

Linear frequency modulated continuous wave(LFMCW)laser radar is a kind of high precision ranging technology,which has non-contact measurements,no blind spots,without cooperative target,high efficiency and high degree of automation,is an important means of large size measurement and obtain the three-dimensional coordinates of the target.Because the range measurement principle is based on the linear frequency modulation ranging of the semiconductor laser platform,the amplitude of the scanning frequency signal is varied,so the modulated optical signal must have the fluctuation of the optical power.The influence of light power fluctuation on ranging accuracy and range resolution is analyzed and verified by simulation.Based on the attenuation characteristics of the controlled object VOA,a closed loop control system is designed to stabilize the FM output optical power.The causes,the power fluctuation of the light source of the optical power fluctuation influence on measurement accuracy are analyzed.The attenuation characteristics of VOA were tested;for stable optical power open-loop correction algorithm is studied and designed based on field programmable logic device(FPGA)closed-loop optical power stability control system;the design of hardware circuit the closed-loop control system comprises a signal processing circuit,signal acquisition circuit and the output of the FPGA minimum system;build a test system of optical power stability,stabilization effect on optical power was tested,and the stability of power system is analyzed.Firstly,the principle of FMCW absolute distance measurement is studied.The reason why the modulation signal produced by laser is used to produce the fluctuation of optical power and the influence of fluctuation of optical power on distance measuring system are analyzed.Secondly,the principle of optical power stabilization is analyzed.The characteristics of VOA were tested,including noise and attenuation,and the attenuation of VOA was corrected,and deduced its specific corrected expression;conceived software scheme of optical power stability of the closed-loop control system and hardware scheme,and according to the design scheme for software design and hardware design;research the negative feedback loop of PID algorithm,and the transfer function of the control system simulation was carried out to determine the specific parameters of PID;the open-loop correction algorithm for digital,and implemented by FPGA.The open-loop correction system of optical power stability is tested,and the effect of open-loop correction on the fluctuation of optical power is verified.The closedloop control system for the test,verify the closed-loop control of laser power fluctuation to the ultimate stability;completed the comparison before and after control effect,and the data are analyzed;effects of error sources in the system accuracy of the season,and the influence of comprehensive analysis.