FPGA Algorithm Realization Based On Double Modulation Laser Ranging

The accuracy and range of length measurement are of great significance to the improvement of science and technology.The methods of laser ranging at home and abroad include flight time method,phase method and interference method.The accuracy of flight time method is not very high.The phase method has a fuzzy distance problem.Interferometry can only measure the relative distance of moving objects.Then this paper proposes a secondary polarization modulation laser ranging system based on the phase method and introduces the basic principle,advantages and some factors that influence the accuracy of this method.This paper introduces the algorithm design of the secondary polarization modulation laser ranging system.The swing method will be used to measure the point in the vicinity of the light intensity minima to detect the optical intensity of the same unknown value on the two sides of the minimum value,and avoid the more obvious interference caused by the system noise when the smaller light intensity is detected.The variable step frequency sweep can reduce the times of sweep ensuring the accuracy.The successive approximation can narrow the range of zeros.The linear fitting reduces the error of the single frequency point and improves the range accuracy.After these processes,two more precise adjacent light intensity points can be obtained,and the results can be calculated according to the formula.We select FPGA as the main control chip of the system.In addition to the specific implementation of the algorithm,control of the microwave source chip,the reading of the results of AD conversion and communication with the upper computer are also included.Algorithm implementation and distance calculation are based on the data length requirement of the range accuracy,and the DSP with powerful operation function is used to process some data.After the implementation and simulation of each module,the controller circuit is designed and debugged.Connect debugged circuits to complete system tests are carried out in the distance measuring system,can prove the validity of the ranging principle and the accuracy of the results.The accuracy can reach up to 10^-5 orders in the case of the range frequency reaching 2000 times/s.