Research On Phase Diversity Detection Technology Under Strong Interference

Active optoelectronic tracking system belongs to common path imaging detection.In addition to the conventional machining and assembly error,rack jitter and other factors that will affect the system's detection ability,the existence of thermal halo and thermal convection in the channel,thermal deformation of the mirror surface of the optical element,and atmospheric turbulence will also cause strong interference to the detection beam of the system.As a result,the system contains low-order large-value aberrations such as defocus,spherical aberration,astigmatism,and coma,which seriously affects the detection ability of the system.Based on the existence of these strong interferences in the common path imaging detection,this paper uses phase diversity wavefront detection technology as the basis to study in depth the method of improving the system's detection ability from the aspect of optimization algorithm under the condition of low-order large-value aberration interference.Firstly,the typical structure of the optoelectronic tracking system is introduced,and the main factors affecting the detection ability of the optoelectronic tracking system are briefly summarized.The imaging model of linear space-invariant incoherent imaging system is constructed and the calculation formulas of coherent and incoherent imaging in spatial and frequency domains are derived.The basic principle of phase diversity to reconstruction the wavefront and restore the target image is derived theoretically,and the simplified objective function formula is obtained according to the maximum likelihood estimation theory.Thus the problem of phase diversity wavefront detection is transformed into the problem of selecting the optimization algorithm to find the extremum of the objective function.According to the theoretical model,the degenerate images of point target and extended target are obtained.Then,the traditional optimization algorithms and their advantages and disadvantages are summarized.A hybrid particle swarm optimization?HPSO?algorithm combining tabu search and particle swarm optimization algorithm is proposed,aiming at the problems that the traditional algorithm is easy to fall into local extremum,slow convergence speed and low convergence accuracy under the condition of large amplitude aberration,and the actual demand that the project needs to improve the detection ability of the system under the condition of low order large amplitude strong interference.For both the point target and the extended target,the optimization detection ability of the algorithm under the condition of large and small aberrations is verified by simulation.At the same time,the simulation compares the convergence accuracy of the developed HPSO algorithm and SPGD algorithm under different amplitude aberrations.Simulation results show that compared with traditional optimization algorithms,HPSO algorithm has the advantages of high convergence accuracy and will not fall into the local extreme value.and it can achieve the convergence precision of 10^-2 when the RMS value of wavefront aberration is less than1?,which fully meets the requirements of the project.Finally,the LC-SLM is used to build the experimental light path and verify the optimization ability of HPSO algorithm in practical application.Firstly,the stripe grating phase method is used to calibrate the LC-SLM and the experimental optical path is aligned.Then the single order aberrations with different amplitudes are generated by the LC-SLM by generating the corresponding grayscale images of different aberrations to verify the optimization ability of the HPSO algorithm for single order aberrations.The experimental results show that the wavefront restoration accuracy of HPSO algorithm for defocus,spherical aberration,coma,and astigmatic aberration is about10,and the experimental results are basically consistent with the simulation results.