Research On Imaging Technology Of Space Target Detection System Based On Relay Image Transmission Of Fiber Optic Transmission Components

Space target optical detection devices are divided into ground-based detection systems and space-based detection systems.The space-based space target optical detection system has many advantages,such as being unaffected by the earth's atmosphere,time-limited,wide in detection coverage,and strong in maneuverability.Therefore,large field of view,long segmental arc,and high-resolution observation are the future development trends of space-based space target optical detection systems.Due to the strict concentricity of all optical surfaces and the symmetrical structure of the optical system of concentric objective lens,the asymmetrical aberration of the entire lens is completely automatically eliminated.With the help of various glass combinations,the optical system can achieve high-quality imaging requirement in a wide visual field,a large relative aperture,and a long wavelength range.imaging needs.Meanwhile,the optical system of the concentric objective lens has a compact structure and is easy to realize miniaturization design,which is very suitable for the resource requirements of space-based payloads.However,the spherical image surface formed by the concentric lens optical system cannot be directly coupled with the plane detector,which is a technical bottleneck that limits its application.With the development of manufacturing technology of optical fiber,the optical fiber panels or optical taper devices makes it possible to flatten the spherical image surface.However,due to the fiber optic image transmission element produces loss in the image transmission process and the discrete sampling characteristics of the element for fiber optic structure,its application is bound to cause a certain impact on the fiber signal-to-noise ratio,modulation transfer function,optical transmittance,image quality,etc.of the space target detection optical system.The influence of optical system of concentric lens +fiber optic image transmission technology on the optical system of space-based wide-area target detection is studies in this paper.The research contents are as follows:(1)Research on the imaging performance of the target detection system based on the components for fiber optic image transmission in the concentric lens optical system+ optical fiber panel + detector coupling optical system.In this paper,the numerical model of the coupling transfer function(Coupled-MTF)of the hexagonally-arrayed element for fiber optic image transmission-CMOS sensor is proposed by establishing a second discrete sampling physical model of the hexagonally-arrayed element for fiber optic image transmission.The convergence relationship between the number of fibers and the Coupled-MTF,the effect of the Nyquist frequency offset on the Coupled-MTF,and the effect of the initial position deviation on the Coupled-MTF were simulated and analyzed.The influence of the components for fiber optic image transmission,the concentric optical system,and the bonding process of the detector on the energy concentration degree is explored through the theoretical analysis and experimental verification.Finally,the experimental test is carried out on the transmittance of the selected optical fiber panel,and the influence of the signal-to-noise ratio is preliminarily evaluated.The relevant research theories,test results and the proposed process control requirements in this paper have engineering guiding significance for the development of optical systems of space-based wide-area target detection.(2)According to the imaging characteristics of space targets in the optical system of space-based wide-area target detection,a detailed signal-to-noise ratio model for space target detection is established in this paper.The relationship between the characteristics of the space target,the transmittance of the optical lens,the transmittance of fiber optic imaging components and the quantum efficiency of the detector and the signal-to-noise ratio are analyzed.Aiming at the difficulty of accurate estimation when the signal-to-noise ratio of weak target detection is low,factors such as dynamic imaging,optical spot dispersion,spectral response,stray light analysis,electronic noise,etc.are introduced completely,forming a full-link,full-variable,high-precision numerical analysis method,which has wide adaptability and strong engineering practicability.(3)Image defect reconstruction and detection target inversion.Defects such as spots,discontinuity,grids and shadows of components for fiber optic image transmission will be reflected in the final image,and the existence of these image defects will seriously affect the detection and recognition probability of space targets.In this paper,a Gaussian process regression reconstruction method is proposed for this kind of problem,and the defective pixels of the star image are reconstructed and corrected,and the correction results are compared with the traditional bilinear interpolation method.The comparison results show that the Gaussian process regression reconstruction method proposed in this paper is superior to the traditional bilinear interpolation method in terms of the reconstruction accuracy of defective pixels and the location adaptability of defective pixels.The Gaussian process regression reconstruction prediction method has a good reconstruction effect on the defect model of 1×1 pixel,2×2 pixels and 3×3 pixels,and the root mean square error elements of star point sample centroid reconstructed 3×3 defect model is better than 0.02 pixels.The research results in this paper can effectively guide the engineering construction of the concentric lens + fiber panel + detector optical system.By studying the signal-to-noise ratio and the final image,the system image quality degradation caused by the introduction of the fiber optic panel can be effectively evaluated,so that the final performance of the application of such an optical structure in target detection can be effectively evaluated.