Design of a large field of view off-axis three-mirror optical system

According to the requirements of a large field of view, miniaturization, and high resolution for space optical systems, this study presents the design of an off-axis three-mirror optical system based on aspheric surfaces. The optical system's structural parameters were determined by calculating and considering the need for manufacture and alignment. The primary and secondary mirrors are designed as spherical surfaces and the tertiary mirror is an aspheric surface. By adopting an aperture off-axis configuration, unobstructed imaging is achieved. The designed off-axis three-mirror optical system has a visible light range, an F number of 4, and a field of view of 16°×6°. Tolerance analysis is also performed. The modulation transfer function (MTF) of the system at various field of views exceeds 0.6 at a spatial frequency of 100lp/mm. All the field of view's spot sizes fall within the Airy disk range, and the relative distortion is less than 1.5%. After considering reasonable manufacturing tolerances, the MTF at a spatial frequency of 100lp/mm still exceeds 0.46. The results demonstrate that the aspherical off-axis three-mirror optical system exhibits excellent image quality, a large field of view and good manufacturability. It meets the design requirements and holds significant value for the research aiming to achieve wider coverage and higher imaging quality for space optical systems.