Research On New Pattern Optoelectronic Imaging Technology Of Anti-laser Reconnaissance And Blinding

To achieve a better imaging quality,we usually fix the photoelectric detector of a conventional imaging system on its focal plane.The focal detector,which is irradiated by a far-field laser beam,will be the secondary luminous object and cause the incoming laser to be reflected along the entrance way.The retroreflection of the optical targets,such as the camera,the telescope and the rifle sight,can be easily detected and distinguished from the background by some laser active reconnaissance devices.Moreover,a great number of the laser active detection devices have been widely applied in many fields,which will significantly threaten the privacy and security of the optoelectronic imaging equipment.Some reasonable and feasible techniques have been applied to reduce or eliminate the annoying retroreflection,thereby reducing the probability of being detected by the active reconnaissance device.However,the conventional methods such as defocusing and filtering achieve the valid retroreflection reduction while suffering significant degradation in imaging quality.Based on the urgent need of laser-defense technology in modern battlefield,this thesis explores the possibility of using two typical computational imaging techniques,namelty the wavefront-coding and the light-field imaging,for anti-laser reconnaissance and blinding.Through theoretical analysis,simulation and experimental verification,the structural design,performance evaluation and parameter optimization are in turns carried out.The main work of this thesis is as follows:1.The laser protection performance of defocused WFC system is studied.Based on the analysis of the the focal-depth extension property,the laser transmission model of the defocused WFC system is then theoretically established by the Fresnel-Kirchhoff diffraction theory.In this model,the transmission characteristics are further studied,and the parameter optimization algorithm is proposed.Furthermore,the WFC lens is designed and manufactured,with which the related experimental research is carried out.The results show that the defocused WFC system can greatly improve the performance of anti-laser-reconnaissance and blinding while maintaining good imaging quality.2.A novel image-plane tilted WFC system is proposed,which could significantly suppress or even eliminate the retroreflection.The theoretical model is firstly established,with which the maximum detector tilt angle and the field of view for precise imaging are derived.The target system is further designed and optimized by Zemax,with simulations of both retroreflection reduction property and imaging quality.Moreover,the final experiments verify the simulation results.The results show that the tilted system could decrease the total echo-receiving power to nearly four orders of magnitude without suffering significant degradation in imaging quality.3.A novel arcsine phase mask is designed and optimized,which improves the focal invariant property of the separable odd symmetrical phase masks.The thesis evaluates the performance of the novel phase mask with four typical criterions: Fisher information,Defocused modulation transfer function,Hilbert space angle,and Digital restoration.The results demonstrate that the arcsine phase mask could restore clear and homogeneous images with both high fidelity and high signal to noise ratio along with a wide range of defocus,proving its superiority in extending the depth of field.4.The laser protection performance of the microlens-array lightfield imaging system is studied.Based on the analysis of the the focal-depth extension property,The laser transmission model of the lightfield imaging system is built.In this model,the transmission characteristics are further studied,and the parameter optimization rules are proposed.The results show that,the peak intensity and the maximum incident power per pixel of the detector can be reduced by nearly two order of magnitude,proving a significant improvement in anti-laser blinding property.5.A novel composite system combing the wavefront coding with the lightfield rendering is designed.The laser transmission model of the composite system is built,by means of which the transmission characteristics and the optimization rules are studied.Furthermore,the imaging and reconstruction process of the composite system is described in detail by simulated imaging experiment.The results show that the composite imaging system could maintain not only the remarkable focal invariant property but also the superior anti-laser blinding property,and restructure the details of the object along with a wide range of focal depth.