Secondary Imaging Architecture for Fast and Ultra-Wide LWIR Optics with Low Rectilinear Distortion

Area of Science:

• Optical Engineering
• Remote Sensing
• Infrared Imaging

Background:

• Wide-swath longwave infrared (LWIR) imaging from Low Earth Orbit (LEO) requires fast optics and rectilinear mapping for thermal mapping and multi-frame registration.
• Achieving a wide field of view (FOV) with low distortion presents significant optical design challenges due to coupled aberrations.

Purpose of the Study:

• To present a novel optical architecture for wide-swath LWIR imaging from LEO.
• To achieve an F/1.2 aperture with a 112° diagonal FOV and low geometric distortion (±5%).

Main Methods:

• A unique architecture using a curved intermediate image to decouple front and rear optical groups.
• Utilized chalcogenide glasses for a 5.7 mm effective focal length lens within a 186.9 mm total track.
• Analyzed performance across the 8-12 μm band, including diffraction limit assessment at 50 lp/mm Nyquist frequency.

Main Results:

• The lens design demonstrates performance near the diffraction limit with stable geometric fidelity across the full field.
• Thermal analysis ( -40 °C to 80 °C) and Monte Carlo tolerance analysis confirm stable imaging performance.
• The design meets the challenging low-distortion requirement, reducing processing needs.

Conclusions:

• The proposed optical design effectively addresses the challenges of wide-swath LWIR imaging from LEO.
• The architecture ensures manufacturing feasibility and stable performance across environmental conditions.
• This advancement facilitates improved thermal mapping and multi-frame registration in space-based remote sensing.