Research On High Precision Laser Location Measurement Technology Based On Four-quadrant Detector

The laser positioning measurement technology based on the four-quadrant detector(4-QD)combines the optical principle and signal processing technology,which has the advantages of high sensitivity,high resolution,fast response and calculation speed,and can carry out the highprecision positioning detection of the irradiation spot on the photosensitive surface,so it is widely used in the military and civil fields.However,the influence factors such as the nonlinearity of the system and the disturbance of the environment limit the detection performance and application domain of the technology,which are specifically manifested as the nonlinear photoelectric response of the detector and circuit,the nonlinear change of the spot distribution,atmospheric disturbance and multi-source disturbance in the measurement environment,etc.Therefore,this thesis studies and models the internal structure,measurement environment and calibration method of the laser positioning measurement system based on 4-QD,and research on the response characteristics,measurement accuracy,measurement scope and application scope of the lifting system.The main research contents and innovation points of this thesis are as follows:Based on the principle and the photoelectric response process of the measurement system,four main modules of its internal structure were studied,including: beam convergence module based on optical lens,photoelectric response module based on 4-QD,signal conversion module based on circuit and noise module of the measurement system.Through the research and modeling of these modules,a set of mathematical model is constructed.In the process,in order to extend the readable range of the photoelectric response signal,a signal solution method based on nonlinear photoelectric response model is proposed.Through to the output signal of integral calculation and model inversion,the pulse signal decoding for light intensity information and used to locate the calculation,so as to expand the linear range of the measurement system.The experimental results show that the accuracy and stability of the method will increase with the increase of sampling frequency.When the sampling frequency is increased to 200 MHz,the model inversion error of the measurement system in this thesis can be stabilized below 3%.It is proved that the solution method can obviously improve the linear FOV and dynamic range of the measurement system.In order to quantitatively analyze the detection performance of the measurement system in the actual environment,three main influencing factors of light source characteristics,atmospheric turbulence and multi-source interference were studied and modeled respectively.Then a multi-source energy distribution model on the surface of the detector after atmospheric transmission is constructed.Combined with the photoelectric response model,this model can simulate and calculate the output signal strength and waveform data of each quadrant according to the system parameters set or calibrated,and then analyze the error distribution of measurement results,which is helpful for system design and battlefield simulation.The experimental results show that the system photoelectric response model constructed in this thesis can accurately describe the response characteristics of the detector in multi-source environment,and simulate the output signal of the measurement system,and then prejudge and simulate the measurement results.A positioning algorithm based on 4-QD is proposed.By adding a correction factor for the edge of the FOV,the algorithm can be modified according to the energy ratio on both sides of the optical axis,which makes up for the defect that the accuracy of the traditional algorithm decreases as the spot moves.The improved algorithm maintains the advantages of traditional algorithms in precision and calculation speed,and does not need to upgrade the hardware while extending its linear range.Simulation and experimental results show that the improved algorithm has obvious advantages in measuring range,accuracy and noise robustness.In addition,a method to refine the internal parameters and environmental parameters of the calibration system is designed,and the corresponding calibration system is constructed.The experimental results show that compared with the traditional calibration method,the improved calibration method improves the measurement accuracy by more than 50%,which proves that the proposed calibration method can make the system obtain higher measurement accuracy.Based on the above research,in order to meet the needs of laser warning with wide field of view,high precision and wide dynamic range,a 4-QD laser warning system based on large field of view is designed in this thesis,and a simulation prototype of the system is built.In the traditional laser angular measurement system,an adaptive module of light intensity based on double-polarized plate structure is added,which enables the system to dynamically adjust the light power on the detector surface to meet the needs of high-light irradiation scene.The experimental results show that the laser alarm prototype designed and constructed in this thesis can maintain the angular measurement error of the incident laser less than 1° within the range of±45°.