Opto-mechanical Structure Design And Analysis Of Synthetic Aperture Radar Optical Processor

With the continuous improvement of resolution,bandwidth and the number of channels,the demand for real-time processing of massive echo data by synthetic aperture radar(SAR)imaging processor is becoming more and more urgent.The use of optical processor combined with spatial light modulator(SLM)has the advantages of low power consumption,small volume,fast processing speed and programmability.These advantages can effectively improve the real-time performance of SAR data processing.However,the application of SLM in real-time imaging of SAR data lacks systematic analysis and evaluation in terms of accuracy,stability and processing efficiency.Therefore,this paper systematically designs and analyzes the optomechanical structure of SAR optical processor.The main research contents are as follows:(1)The system working model of SAR optical processor is established.The model synthesizes the Fourier transform characteristics of the lens,the spatial filtering principle of the 4f system and the wavefront modulation mechanism of SLM.The Digital Micromirror Device(DMD)and SLM are used to filter the amplitude and phase information of SAR data respectively,which guarantees the accuracy of the SAR optical processor theoretically.(2)According to the optical processor system model,the optical system of 4f filter module,laser beam expansion module and spectral modulation module is designed and analyzed.Based on the relevant parameters of DMD,SLM and other components,the design of Fourier transform lens and 4f optical system is completed,the imaging quality tends to the diffraction limit is analyzed,and the reasonable optical design tolerance is given;Then,the beam expanding effect of the laser beam expanding system is evaluated by using the point diagram,and the modulation quality of the optical system of the spectroscopic modulation module is evaluated by using the optical platform simulation experiment.Through the analysis and evaluation of three sub-optical systems,the stable implementation of SAR optical processor is ensured in the optical system.(3)The modular opto-mechanical structure of the optical processor is designed.For the 4f spatial filter module with high requirements,the flexible mirror base design of a single lens is realized by using the multi-objective integrated optimization method,and the overall structure design of the module is completed by using the static and dynamic analysis method;The laser beam expander module and spectroscopic modulation module have also completed the support structure design of their respective optical elements,which fully meet the static and dynamic indexes.The overall size of the assembled SAR optical processor is 585mm×390mm×162mm,compared with the inclined plane optical processor,not only the size is further reduced,but also its accuracy and stability are improved.(4)The static and dynamic analysis of the whole structure of the optical processor is completed by using the Integrated opto-mechano thermal analysis method.Using the modulation transfer function(MTF)value at the cut-off frequency of the lens as the evaluation standard,the static evaluation process including self gravity analysis and thermal stress analysis is established.The analysis results show that the system meets the imaging requirements of MTF greater than 0.4 at 55lp/mm under self weight condition.Through thermal analysis,it is concluded that the suitable temperature range for high-precision imaging of optical processor is 19?26.5?;In the dynamic analysis,it is ensured that the fundamental frequency of the whole structure is 239.5hz,avoiding the disturbance frequency range of 0?100Hz.At the same time,under the excitation of1 G acceleration,the magnification of the structural response peak is less than 5,which fully meets the dynamic stiffness requirements of the optical processor.Through the static and dynamic analysis and evaluation of the whole structure,it is ensured that the SAR optical processor can fully meet the requirements of high-precision and high stability data real-time processing,which provides a certain reference for the systematic design and analysis of SAR optical processor.