Design of a large-aperture cryogenic very long-wave infrared reflective optical system

The very long-wave infrared (VLWIR) spectrum (8-16μm) contains critical atmospheric information such as humidity, CO₂ content, cloud structure, and thermal profiles. Leveraging its advantages in passive detection and anti-interference capabilities, this paper proposes a large-aperture, small F-number, broadband reflective optical system design for VLWIR applications. The system innovatively adopts a coaxial-off-axis composite optical axis configuration with a five-mirror structure. By integrating free-form surface aberration correction technology, it achieves a 2°×2° field of view (FOV) under a 1000 mm aperture and F/1.8 while addressing traditional limitations of coaxial reflective systems, such as severe central obscuration and energy loss. The obscuration ratio is reduced to 15%. The system achieves diffraction-limited energy concentration across the full FOV within the 8–16 μm spectral band. Its compact structure, excellent resistance to thermal and mechanical stresses, and compatibility with cryogenic environments (80 K) make it suitable for spaceborne remote sensing and deep-space exploration, offering a novel optical solution for high-reliability, lightweight space payloads.