Research On Performance And Range Estimation Technology Of3D Flash Ladar

3D Flash Laser Detection And Ranging (LADAR) system can generate threedimensional (3D) images of the target in a single pulse，and have the advantages of highspeed, low weight, small volume. All these make it to be one of the important trend of theLadar development. However,3D flash Ladar is quite different with3D scanning Ladar notonly in the hardware, but also in the data processing and data accuracy. Currently, muchattention is paid to the development of detector arrays and the improvement of detectorperformance, but little to the performance of the system integration and range estimatealgorithm for accurate data processing. Therefore, the research of the system performanceand range estimate algorithm of the3D Flash Ladar system has important theoretical andpractical value.This thesis research the imaging performance of the3D Flash Ladar system, andanalyze the relation between system performance and system parameters, including themaximum detectable range, the detection probability, the false alarm probability, the SNR,the range accuracy and the range resolution are discussed, which are used as basis forsystem design and range estimate algorithm. At the same time, this thesis research the rangeestimate algorithm of the3D Flash Ladar system. Compared with the traditional algorithm,the range estimate algorithms proposed in this paper improve the range accuracy greatly.The main work and the contribution in this paper are as follows:(1) The3D Flash Ladar system is analyzed with the detection probability, the falsealarm probability, the maximum detectable range and the SNR discussed. It is proven thatthe3D Flash Ladar can be considered to be a result of an incoherent imaging process. TheLadar equation in large field of view is modified and the formula of the detectionprobability, the false alarm probability is derived. The influence of the detection probability,the false alarm probability are analyzed.(2) The range accuracy of3D Flash Ladar system is analyzed based on the parameterestimation theory. According to the theory of mathematics statistics, the Cramer-Rao lowbounds (CRLB) of range estimate variance is analyzed, formulas of CRLB are given.Monte Carlo simulation results validate the CRLB of range estimate variance is effective.Finally, the influences of the accuracy of3D Flash Ladar system are analyzed. Some wayshave been given to improve the range accuracy of the target through theoretical derivation.(3) According to the theory of mathematics statistics, CRLB of range resolutionestimate variance is analyzed.3D Flash Ladar system pulse models are researched. Formulas of CRLB are given. The influences of the range resolution of3D Flash Ladarsystem are analyzed. The results show that higher SNR values and sampling rate aids inrange separation estimation efforts. In addition, there is an optimal pulse-with that producesan optimal range resolution for a particular sampling rate.(4) Multi-surface ranging with the use of3D Flash Ladar can also be useful inaccurately discriminating camoufaged targets of interest. In order to estimate multiplesurfaces in3D flash imaging Ladar well and truly, a multiple surfaces range estimatealgorithm in3D flash imaging Ladar via Expectation maximization（EM）is proposed. Thisalgorithm can estimate the point spread function(PSF) of imaging Ladar and the targetrange information simultaneously. Simulation examples show that the multiple surfacerange estimate algorithm derived in this work improved range estimate over traditionalmixed Gaussian matching and Wiener filter by up to70%and40%respectively.(5)An algorithm to enhance the range estimate in the condition of under sampled. Ladarpulse model is analyzed. A range estimate algorithm using EM of under sampled target in3D Flash Ladar is proposed. The range estimate accuracy is improved through fusion of2Dintensity image and3D image data. Simulation examples show that the under sampledtarget range estimate accuracy is improved obviously over nearest，linear and cubicinterpolators without known the point spread function.(6) An algorithm to enhance the range estimate in the presence of Anisoplanaticatmospheric turbulence. An anisoplanatic optical transfer function (AOTF) is derived. A3D Flash Ladar range estimate algorithm using EM is proposed. Target range informationand optical transfer function can be estimated precisely through this algorithm. Simulationexamples show that the range estimated algorithm derived in this work improves rangeestimated over the Gaussian match and the range estimated using isoplanatic OTF by70%and15%receptively. Additionally, The additional anisoplanatic blur components modeledby the AOTF increased the accuracy of estimation of Fried’s seeing parameter from8%towithin4%using simulated data. This algorithm will contribute a lot in the realistic3D flashLadar range estimation.