Multi-spectral Co-phasing Error Detection In Optical Synthetic Aperture Telescopes

According to Rayleigh criterion,the maximum resolution angle becomes smaller and the spatial resolution is higher when the aperture size of the telescope increases.The telescopes' sizes are becoming larger and larger these years.With the development of science and technology,astronomical observation,remote sensing imaging and other fields require more and more high resolution of detectors.Because of the limitation of the current manufacturing technology,the traditional single-aperture telescope can no more improve the resolution by expanding the aperture,and the optical synthetic aperture imaging technology,which can obtain a larger equivalent aperture resolution by means of separated mirror structure or combination of telescope arrays,has been proposed and studied.All the optical synthetic aperture systems face a serious challenge to improve the imaging resolution,the cophasing error.Only being cophased,optical synthetic aperture systems could reach their maximum resolution,and the construction of them were meaningful.As one of the key technologies to improve the resolution of optical synthetic aperture systems,the co-phasing error detection technologies have been widely studied.The works in this paper are also about co-phasing error detection.Firstly,optical synthetic aperture systems are classified into types based on their structure characteristics.The development status of different types of synthetic imaging telescopes are reviewed,and a unified theoretical model is established to study the effects of different types of co-phasing errors on the imaging quality of optical synthetic aperture systems.This paper has analyzed the source of co-phasing errors,summarized the existing cophasing error detection technologies,discussed their limitation.Also,the multi-spectral measurement method,which can be used to extend the cophasing error capture range,has been analyzed.Secondly,multi-spectral cophasing error detection technology based on phase-shifting has been studied.The principle of multi-spectral cophasing error detection technology based on phase-shifting has been described in detail.The simulation model of cophasing error detection for a golay-3 optical synthetic aperture system is established,and the multi-spectral cophasing error detection technology based on phase-shifting is tested and verified on this simulation model.Thirdly,the defects and limitations of the multi-spectral cophasing error detection technology are analyzed,and an improved method to address these problems by using deconvolution is proposed.The improved method is verified by simulation,also its cophasing error detection accuracy is analyzed in the presence of various wave aberrations.Then the multi-spectral cophasing error detection technology based on sub-aperture spatial modulation is proposed and implemented.The theoretical principle of this new method is expounded.Also,the method is verified by simulation and compared with the phase-shifting based multi-spectral cophasing error detection technology method to figure out the advantages and disadvantages of the method.Finally,the key device of multi-spectral cophasing error detection technology for phase-shifting modulation,phase-shifter,is designed,and the experimental platform of optical aperture synthetic imaging is built based on the phase-shifter.The multi-spectral co-phasing error detection technology based on phase-shift modulation and the multi-spectrum co-phasing error detection technology based on pupil space modulation are experimentally studied,and the correctness and feasibility of the two methods are verified.In the experiment,these two methods have successfully detected the piston errors,the capture ranges are ±8?m and ±10?m,and the accuracies are 18 nm and 24 nm,respectively.