Research On Focusing Technology Of Three Line CCD Mapping Camera Based On Satellite

Spaceflight mapping has broad application prospects in the military, nationalconstruction and other fields, which promote spaceflight mapping camera to developradpidly.The transmission type three line CCD mapping camera was proposed,because it can improve the mapping accuracy in area, where there are no groundcontrol points. The three line CCD mapping camera has the merits that it can getinflight stereo imaging, and it can reconstruct the exterior orientation elements fromthe imaging.Thus three line CCD mapping camera play more important role in thefield of spaceflight mapping, and many more researcher study on the kind of spacephotography. While focusing technology is one of the key technologies in thedevelopment of spaceflight mapping camera. As a important component of spaceflightmapping camera, focusing system determine not only the image quality but also themapping accuracy. With the research on a project of three line CCD mapping camera,this thesis emphasized on discussing the focusing technology, the design andrealization of focusing system for the three line CCD mapping camera.The specificstudy in this thesis are as follow:1. The optical system imaging principle of spaceflight camera was analyzed, andthe push-broom imaging model for line CCD camera was established, key technicalindicators was also analyzed. The reasons of defocusing was discussed in details forspaceflight camera. The influence degree for MTF and mapping accuracy leading toby defocusing was discussed and analyzed. The focusing evaluation function based onMTF and power spectrum was proposed.and simulated. 2. The composing and imaging principle for three line array CCD mappingcamera was introduced, and the three line CCD space strict parallel converted to theCCD focal plane was analyzed in the technical requirements Focusing scheme wasproposed for the three linear CCD mapping camera. The components and workingprinciple of focusing system was introduced.3. The focusing system is a set of optics, mechanics, electrics aspects of thecontrol system, the focusing performance should be stable, quick and precision.Therefore, the various components of the focusing system was designed and analyzedin detail to ensure that the focusing precision meet the requirement of three line CCDmapping camera, which including focusing step motor, driver power circuit, CCDfocal plane. According to the characteristics of CCD focal plane and the focusingprecision of mapping camera, three gear transmission mechanism was designed, andtransmission ratio was calculated in detailed. Accroding to the error theory, every partof focusing system was analyzed and calculated, including the focusing encodersensitivity, drive mechanism,error analysis. Focusing software was designed based onfunctional requirements for the focusing system software, research alogrithm oftraversing and climbing algorithm were introduced. It was verified that Coarsefocusing method and fine focusing method meet the precision requirement.Thefocusing stratedy suitable for three linear CCD mapping camera was proposed, andtwo contrasting focusing method for this focusing strategy were described in detail.4. The test results indicted that the focusing system designed for three line CCDmapping camera can meet the focusing technical requiements. The curve of focusingbased on various temperature was completed in the thermo-optical test. It verified thatthe focusing system could work in the thermal vacuum tank working conditions. Theposition curve of CCD focal plane MTF vs. temperature conditions was tested.whichwas the indicator and guiding role for three line CCD mapping camera for working inorbit...