Research On Wide FOV High Resolution Earth Observation System Based On Multi-scale Stitching Imaging

Wide field of view (FOV) and high resolution is always a couple of imaging characteristics which are opposite and unity. Wide FOV offers overall information of the target field and high resolution contributes to the details. Imaging system with wide FOV and high resolution being able to acquire large observation field and resolving power is widely used in the area of Earth observation such as (unmanned areal vehicle) UAV aerial imaging, terrain mapping and crops survey.Traditional imaging method to acquire wide FOV and high resolution can be divided into two ways:mechanical scanning and multi-camera imaging. Mechanical scanning means scanning the target field and output a whole image after image processing. And the FOV and resolution are controlled by scanning angle and scanning precision. But mechanical scanning is not able to image instantly, which makes it unfit for dynamic observation. Multi-camera imaging means apply several cameras shoot simultaneously and each camera is in charge of a part of imaging field, keeping partial overlapping with the adjacent one to do the image stitching in next progress. The way of multi-camera imaging is able to realize dynamic observation, but the FOV of a single camera is still restricted due to optical distortion. And adding cameras to enlarge FOV and increase resolution will make the system more complicated and enlarge the volume and weight. Thus make it difficult in optical matching and mechanical assembly.In this paper, an imaging method based on multi-scale theory and monocentric lens design is proposed, which conquers the optical distortion in at the edge of the imaging field appeared in traditional optical design. It is able to wide FOV and high resolution simultaneously. An imaging system is constructed based on this method and it consists of two identical imaging module which are stacked up and down. Each module consists of an objective lens and a set of multi-aperture optical array and every aperture of the array is in charge of a part of the whole FOV. The two imaging module are staggered a certain degree to make sure each sub-FOV of a aperture has overlapping fields with others. This unique design makes the system more compact and helps to limit the system volume and weight and therefore the system is more suitable for observation, expanding the application range.The research contents of this paper are listed as:1. Make a detailed introduction of imaging system with wide FOV, high resolution used for Earth observation, including the research background, present development situation and the advantages and shortcomings of each one. And the imaging method in this paper is proposed.2. The optical design method and imaging principle is stated in detail. We construct the math module of the imaging system and deduct the math expressions of the optical parameters.3. A design model is presented according to the imaging method and parameter index. And we make a detailed analysis to its imaging characteristic and design the optical mechanical structure.4. An imaging system is finally built and we use the system to do some experiments to test the imaging performance.