Design of Vehicle-Mounted LWIR Optical System Using Diffractive Aspheric Lens and Analysis of Its Athermal Characteristics

This study presents the design and analysis of a vehicle-mounted long-wave infrared optical system for a 640 × 480 uncooled detector with a 12 μm pixel pitch. To improve manufacturability and cost efficiency, the optical system was configured with two chalcogenide glass lenses, providing a field of view of 42° × 31.2°, an F-number of 1.09, and an effective focal length of 10.7 mm. The optimized design satisfied the required optical performance, including distortion below |15|%, while maintaining adequate MTF and relative illumination over the full field of view. Athermal performance over the temperature range from -20℃ to 60℃ was achieved by employing IRG26(As40 Se60) and balancing the temperature- dependent focal shifts of the two lenses, demonstrating the feasibility of the proposed system for vehicle thermal imaging applications.