Off-axis Reflective Optical Systems For Space Camera Study

The space camera is one of the most advanced optical equipments in obtaining earth surface information from the space. With the development of the optical designing, manufacturing and alignment technology, the performance of the optical camera is moving forward quickly.Compared with the co-axial optical systems, the new off-axial, decentered and tilted systems have greater potential in enlarging the field of view, enhancing the discerning potential and restraining stray light, etc. The three-mirror astigmatism systems have the merit of less components, no obscuration, long focal length, big field coverage, wide spectrum, excellent stray light eliminating ability, and high modulated transfer function output. In the meantime, the non-symmetric layout of the system brings considerably difficulty to the structure design, optics manufacturing and system alignment process. So it is a hot-spot in recent studies and is a technical obstacle as well.The dissertation focuses on the reflective optical system used in space camera, including describing the characte of serial typical space camera, i.e., the optical component of IKONOS camera, the principle of push broom CCD space camera, and the modulation transfer function (MTF) of the space camera were introduced.The two-mirror system and three-mirror system were described, and the method of calculating the original co-axial structure parameters, the effect to modulation transfer function from the unavoidable central obscuration of co-axial system were analyzed. The structure of off-axial systems was discussed and examples of design were offered to illustrate the above mentioned method. The evaluation proves that the optimization of the decenter, tilt degrees and aspheric coefficients were appropriate to the image quality.