Research On Techniques For On-Orbit Calibration Of Space Optical Imaging Systems Based On Auto-collimation

The on-orbit geometric calibration technology of an auto-collimation principle space camera is to monitor the inner orientation elements of a space camera without shooting range calibration,including the principal point,effective focal lengths,and the rotation of the visual axis in the X,Y,and Z directions.Because of without shooting range,low cost,simple system and real-time monitoring,this technology is very suitable for the on-orbit calibration of the aerospace mapping camera for inner orientation elements.This dissertation mainly verified the feasibility of an on-orbit geometric calibration technology on a 4 space camera,analyzing the main effects of decreasing the system calibration accuracy and proposing an optimized solution to improve its accuracy.At first,after introducing the working principle of the auto-collimation calibration system,we calculated the space camera's parameters by monitoring the movement of the image spots and deduced the mathematical model and imaging formula,constructing the bias matrix between the image point position and structure parameters.Second,because of the structure of the off-axis three-reflection space camera,the light sources,detectors,beam splitters and mirrors were added into the camera for designing a auto-collimation calibration system.Moreover,to verify the reliability of the system,we simulated the developed geometric calibration method under the ideal conditions.According to the mathematical model and the simulated results,we analyze the main effects of decreasing the calibration system's accuracy,including the centroid positioning error,the system error of the turning mirror focusing,and the error of system processing and assembly adjustment.Besides,we proposed an optimization plan for the calibration system,improving the positioning accuracy of the system's centroid by using the traditional algorithms,calculating the system focusing and limiting the tolerances of specific structural parameters.Finally,we built the experimental platform to verify the on-orbit geometric calibration technology of a auto-collimation space camera.The experimental results show that the calibration accuracy of the system focusing was 0.027mm;The calibration accuracy of the boresight X direction rotation was 0.403?;the calibration accuracy of the boresight Y direction rotation was 0.386?;the calibration accuracy of the boresight Z direction rotation was 9.752?.After optimizing the calibration accuracy of the experimental system,the calibration accuracy of the system focusing was 0.0097mm;the calibration accuracy of the boresight X direction rotation was 0.117?;the calibration accuracy of the boresight Y direction rotation was 0.117?;the calibration accuracy of the boresight Z direction rotation was 2.645?.The experimental results indicated that the developed calibration method is efficient for improving the accuracy of the system.