Research On Optical Synthetic Aperture Primary Co-phasing Error Correction Technology

In traditional optical telescopes,the size of telescope observation aperture is one of the most key factors affecting its resolution.In ideal situation,when the observation wavelength is fixed,the aperture determines the detection resolution of the telescope system.In fact,limited by processing technology,manufacturing materials,manufacturing cost and other factors,it will greatly increase the manufacturing cost with the increase of the aperture size of the optical system.Therefore,the multi-aperture synthetic imaging technology based on several small coherent telescopes came into being.In multi-aperture coherent synthetic imaging,the problem of the co-phasing error is one of the most key problems.The co-phasing error is caused by a certain phase error between different apertures,which leads to the decline of coherent synthesis quality and affects the imaging effect.Aiming at the large-scale translation error in the co-phasing error,this paper carries out primary co-phasing detection to improve the aperture coherent synthesis ability of wide-band synthetic aperture imaging,and the imaging ability of multi-aperture synthetic imaging telescope.In this paper,the detection and calibration of large-scale translational co-phasing error of multi-aperture and wide spectrum synthetic aperture telescope system is taken as the research goal.According to the incoherent imaging theoretical model of traditional single aperture and synthetic aperture imaging telescope,the essential reason for the improvement of synthetic aperture imaging resolution is demonstrated based on the space-frequency domain,and the causes of co-phasing error and its impact on the imaging system are analyzed and evaluated.Through theoretical analysis,it is found that the image plane distribution of synthetic aperture imaging is modulated by three important factors: multi-aperture coupling fringes,the modulation of fringes by translation error,and sub-aperture airy spots.The main research work of this paper focuses on the analysis of the three elements in the image plane with the co-phasing error to deal with the primary co-phasing problem based on the analysis results.The main research of this paper include:(1)For multi-aperture coupled fringes,a multi-aperture coupled fringes decoupling method based on Radon transform is proposed.On the basis of not relying on other optical components,this method can realize the separation of different baseline sub aperture pairs through Radon transform and Fourier transform,simplifying the complex multi-aperture co-phasing problem to the two-aperture co-phasing problem,and greatly reducing the co-phasing difficulty of the system.(2)Aiming at the modulation of fringe caused by translation error in wide spectrum scene,a wavelength coding translation error detection method based on multi wavelength wide spectrum illumination is proposed.By encoding the wavelength of incident light,this method avoids the 2? ambiguity problem and local optimal problem in the traditional co-phasing method.In the simulation,it is verified by Gaussian distribution and Fabry Perot modulation spectrum.Compared with the traditional method,this method can further expand the detection range of the traditional translation error primary co-phasing method.(3)Aiming at the extraction and restoration of sub-aperture Airy spot in motion blur,a local point spread function extraction algorithm based on Wigner distribution is proposed.The gradient of motion blurred target is analyzed by Wigner distribution,and the blur kernel fringe is successfully extracted by multi-point sampling of blur interference term.Theoretical analysis and experiments show that the non-uniform motion blur kernel of the target can be accurately extracted through small sampling area or rough edge detection.Therefore,this method can reduce the sampling area to the same size as the target blur kernel for ensuring the accuracy.This work can be widely used in the restoration of small motion blurred objects or targets with unclear edges to realize image restoration.