A Coaxial and Off-axial Integrated Three-mirror Optical System with High Resolution and Large Field of View

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    A novel optical design for high resolution, large field of view (FOV) and multispectral remote sensing is presented. An f/7.3 Korsch and two f/17.9 Cook three-mirror optical systems are integrated by sharing the primary and secondary mirrors, bias of the FOV, decentering of the apertures and reasonable structure arrangement. The aperture stop of the Korsch system is located on the primary mirror, while those of the Cook systems are on the exit pupils. High resolution image with spectral coverage from visible to near-infrared (NIR) can be acquired through the Korsch system with a focal length of 14 m, while wide-field imaging is accomplished by the two Cook systems whose focal lengths are both 13.24 m. The full FOV is 4°×0.13°, a coverage width of 34.9 km at the altitude of 500 km can then be acquired by push-broom imaging. To facilitate controlling the stray light, the intermediate images and the real exit pupils are spatially available. After optimization, a near diffraction-limited performance and a compact optical package are achieved. The sharing of the on-axis primary and secondary mirrors reduces the cost of fabrication, test, and manufacture effectively. Besides, the two tertiary mirrors of the Cook systems possess the same parameters, further cutting down the cost.


    Three-mirror system , Telescopes , Optical system design , On-axis , Off-axis


    Optical systems characterized by large apertures, long focal lengths and large fields of view (FOVs) are required by the application of high resolution, large spatial and spectral coverage space-to-earth observation. Compared with refractive optical systems, mirror systems are widely utilized in space-borne remote sensing, because of the absence of chromatic aberration, easiness of lightweight design [1], and the compact configuration.

    Three-mirror systems are commonly adopted by remote sensors for the advantages of more freedoms in optimization, higher image quality and larger flat focal plane etc. over two-mirror systems. There are mainly three principal categories of three-mirror systems for various applications: the Wetherell type [2, 3] [Fig. 1(a)], the Korsch type [4, 5] (