基于主动相干光学合成孔径超分辨成像的空间目标探测系统

Space Object Detection System Based on Active Coherent Optical Synthetic Aperture Super-resolution Imaging

基于宏观反射式傅里叶叠层成像理论,提出一种主动相干光学合成孔径超分辨成像空间目标探测系统。采用主动相干光源配合单个小孔径相机,采集目标低分辨图像序列,通过傅里叶叠层拼接算法重构接近等效合成孔径倍率的超分辨图像。给出了系统的总体方案和详细设计,并通过搭建的宏观反射式近红外主动相干光学合成孔径超分辨成像地面实验装置验证了系统的超分辨成像能力。该系统有望通过小孔径实现等效合成孔径全天时高分辨成像效果,大幅缩减载荷口径需求。弥补传统空间目标探测系统夜间成像能力的不足,提升空间目标夜间探测能力。

There are a large number of communication satellites and abandoned satellites in the geostationary orbit.High-resolution all-time imaging of space targets can afford useful information such as target fine structure,star attitude and working situation.Fine detection of large space debris also can provide some information for spacecraft rapid evasive.But the traditional passive space target detection payload is mainly faced with some problems.For example,the single-aperture imaging system has difficulties in optical processing and is limited by rocket carrying capacity.The space block deployable imaging system and passive optical synthetic aperture imaging system have sub-mirror shape control and phase adjustment problems.In addition,the film diffraction imaging system has serious chromatic aberration,resulting in poor imaging quality.Moreover,the night high resolution imaging ability of infrared payload is insufficient.So it is of great significance to carry out research on new space-based space object detection technology,realizing high-resolution and all-time detection of the space object.In this paper,a new type of active coherent optical synthetic aperture super-resolution imaging space object detection system is proposed based on the theory of macro-reflection Fourier ptychographic imaging.The theoretical model of macro reflection active coherent optical synthetic aperture super-resolution imaging based on light source scanning is shown.Then a general idea of"large field of view search imaging guide and small amplitude width active coherent optical synthetic aperture super-resolution imaging"is proposed.Where the large field of view search imaging system carried by the satellite platform provides pointing information of the target,the small amplitude width active coherent optical synthetic aperture super-resolution imaging system captures and aims the target under the guidance of the steering mechanism of the satellite platform.Then super-resolution imaging is performed.The small amplitude width active coherent optical synthetic aperture super-resolution imaging system is the main component of the space-based space object detection system.It includes an active coherent light generation unit,an optical imaging unit and an image superresolution reconstruction unit.The macro reflective active coherent optical synthetic aperture system under a camera scanning mode requires frequent maneuver of the payloads,rapid attitude adjustment and high precision pointing.Considering the feasibility of space-based applications,a light source scanning mode is chosen instead of camera scanning mode.The operating principle of the new type of active coherent optical synthetic aperture super-resolution imaging space object detection system is as follows.The active coherent optical synthetic aperture super-resolution imaging space object detection system mainly adopts two working modes:global detection and regional detection.When it takes global detection mode,the spacebased space object detection system operates at an orbit lower than the GEO,with a typical value of GEO-150km orbit.The space object detection system achieves tracking and imaging of global targets at GEO through relative drift of forward position.When it takes regional detection mode,the space-based space object detection system operates at an orbit higher than the GEO,with a typical value of GEO+150 km orbit.The space object detection system carries out the round-trip detection of a given area by forward drift,backward drift,ascent and descent movements formed by the altitude difference with the GEO orbit,so as to realize the tracking and imaging observation of the target in the corresponding area.Specifically,the near-infrared active lighting source is adjusted by the optical phased array,and then the sequential output of each beam is realized through computer program control.Due to the difference of orbital altitudes,a speed difference is produced between the active coherent optical synthetic aperture superresolution imaging space object detection system and the target.In order to ensure the uniform scanning of coherent beams against the target,the system position feedback corrector is used to calibrate the beam scanning in real time.Then N×N frames of low resolution images are collected.Finally,the superresolution image of space object is reconstructed from these low resolution images by using Fourier ptychographic algorithm.At the same time,a prototype of macro reflective active coherent optical synthetic aperture super-resolution imaging system is built,and some ground experiments are carried out.Results show that the system has super-resolution imaging capability.Finally,the feasibility of active coherent optical synthetic aperture super-resolution imaging technology is further confirmed.The active coherent optical synthetic aperture super-resolution imaging space object detection system proposed in this paper has all-time imaging capability.It is expected that this technology can greatly reduce the aperture requirements of space object optical detection payload and effectively reduce the difficulty of system development.It not only provides a new technical approach for space-based space object detection,but also provides a method for low Earth orbit to ground high-resolution imaging.