Design of a fold-back common aperture optical system for laser infrared composite detection system

Traditional laser ranging and infrared target tracking systems often employ separate optical paths, leading to increased system weight, alignment complexity, and challenges in maintaining coaxial tracking accuracy. To address these limitations, this paper proposes a novel common-aperture optical system that integrates laser ranging and long-wave infrared target tracking into a unified design. The system utilizes a 640×512 cooled long-wave infrared detector and employs a catadioptric secondary imaging structure to achieve compactness and high performance. The long-wave infrared subsystem operates in the 8~10μm spectral band with a focal length of 320.5mm, a 2°×2° field of view, and an F-number of 2, ensuring high sensitivity for target detection in low-visibility conditions. Simultaneously, the laser ranging subsystem operates at 1.054~1.074μm with a 900mm focal length, providing precise distance measurement capabilities. By adopting a co-aperture design, the system eliminates the need for separate optical paths, significantly reducing weight and alignment errors while improving tracking stability. The proposed optical system was rigorously simulated and optimized to ensure performance across a wide operational temperature range (−40°C to +60°C). Results demonstrate that the system maintains high imaging quality and ranging accuracy under varying thermal conditions, making it suitable for harsh environments. The compact and lightweight design further enhances its applicability in airborne or mobile detection platforms. Potential applications include military surveillance, unmanned aerial vehicle tracking, and autonomous navigation systems, where real-time target detection and precise ranging are critical. Future work may explore adaptive optics integration to further enhance performance in dynamic scenarios. This study provides a practical and efficient solution for next-generation laser infrared composite detection systems, offering improved reliability and versatility in complex operational environments.