The CCD plane of the space tridimensional mapping camera will be deviated from the focal plane(including the CCD
plane deviated due to camera focal length changed), under the condition of space environment and vibration, impact
when satellite is launching, image resolution ratio will be descended because defocusing. For tridimensional mapping
camera, principal point position and focal length variation of the camera affect positioning accuracy of ground target,
conventional solution is under the condition of vacuum and focusing range, calibrate the position of CCD plane with
code of photoelectric encoder, when the camera defocusing in orbit, the magnitude and direction of defocusing amount
are obtained by photoelectric encoder, then the focusing mechanism driven by step motor to compensate defocusing
amount of the CCD plane. For tridimensional mapping camera, under the condition of space environment and vibration,
impact when satellite is launching, if the camera focal length changes, above focusing method has been meaningless.
Thus, the measuring and focusing method was put forward based on astigmation, a quadrant detector was adopted to
measure the astigmation caused by the deviation of the CCD plane, refer to calibrated relation between the CCD plane
poison and the asrigmation, the deviation vector of the CCD plane can be obtained. This method includes all factors
caused deviation of the CCD plane, experimental results show that the focusing resolution of mapping camera focusing
mechanism based on astigmatic method can reach 0.25 μm.