Design of large field of view multi-spectral off-axis three-mirror reflective optical system

Aiming at the application requirements of space remote sensing observation of light and small multispectral imaging technology, a wide field of view multispectral small off-axis three-mirror optical system based on linear gradient filter is designed. The spectral coverage range is 430nm ~ 900nm, the field of view is 6.3 ° × 4.5 °, F number is 8. The focal length of the optical system is 350 mm, and the system uses staring scanning to image the ground. The detector is 8424 × 6032 array detector, the pixel size is 4.6μm. The light splitter adopts linear gradient filter, and the aperture diaphragm is set at the secondary mirror, so that the size of the main mirror is close to that of the three mirrors, and the size of the whole system is reduced. Finally, the design results show that the whole system has compact structure and good imaging quality. The modulation transfer function (MTF) of the optical system in each spectrum band of the full field of view is greater than 0.3 at the Nyquist frequency of 108lp/mm. MTF and Spot Diagrams are close to the diffraction limit, which can meet the application requirements.