Research On The Key Technologies Of Phase Shift Laser Rangefinder System Based On The Maximum Likelihood Estimation

Measurement is an important tool for human development and progress.Since the United States developed the world's first ruby laser in the 60's of the last century,laser measurement technology has begun rapid development,and has been applied in many fields.Compared to the general electromagnetic wave,laser has good directivity,monochromatic outstanding,high resolution and strong anti-jamming capability,so the accuracy and range of the laser measuring equipment are far beyond the similar equipment.Laser range finder is a kind of widely used laser measurement equipment,and there are mature products in both protection level and civil level.This paper introduces in detail the design of hardware and software of phase laser range finder.First of all,in theory,the methods to estimate the common sine signal phase are analyzed,and through the simulation,this paper determined to use the maximum likelihood algorithm with the highest precision.The maximum likelihood algorithm,with the sampling points more than 20000 points and 40 dB Gauss white noise background,has a measurement accuracy of 0.002 degrees.This algorithm meets the requirement of system well.Then according to the theory,this paper designs a set of phase laser ranging system in order to verify the accuracy of the phase measurement and stability of maximum likelihood algorithm.This system adopts DDS technology as the signal source.The technology has the advantages of high frequency resolution and good continuity of the output phase.The DDS output sine signal,a road signal generates phase delay after the laser diode modulation,and the photoelectric detection receiving end.Then using double channel ADC on the delayed signal and the other way without signal laser emitting and receiving data sampling,the collected data is fed into the SRAM cache,then through the FPGA and USB communication interface,data is uploaded to the PC.Finally the phase difference of the two signals is estimated in the PC using maximum likelihood algorithm.Finally,this paper built a hardware experiment platform based on the design concept,through experimental analysis,and verified the feasibility applying the maximum likelihood algorithm for laser ranging system phase,the phase measurement accuracy of 0.3 degrees.At present,most phase measurements use square wave,and this paper put forward the scheme of directly measuring phase of sinusoidal signal.The research lays the foundation for thefollowing.