Design of a compact infrared panoramic optical system for unmanned aerial vehicles

Infrared imaging system is widely used in unmanned aerial vehicle (UAV) detection because of the advantage of precise monitoring and anti-interference. However, it is difficult to simultaneously achieve large field of view (FOV) and light weight. In this paper, we propose a compact infrared panoramic annular lens (PAL) system with a large FOV and a three-piece simple structure, which contains three standard spherical lenses and has a FOV of (30 degrees similar to 100 degrees) x360 degrees, total length of 51.6mm, maximum diameter of 72 mm, focal length of 2.2mm, and F number of 3. The modulation transfer function of the system is higher than 0.7 at the Nyquist frequency, and F-theta distortion is controlled to less than 2%, which can meet the requirements of UAV detection. In addition, we use optical compensation method to achieve athermalized design in the range of -40 degrees C similar to+80 degrees C. The system possesses low sensitivity in tolerance, therefore we design a straight-tube mechanical structure for the system to simplify the assembly process and ensure the assembly precision at the same time. The PAL system we proposed is easy to be carried by UAVs due to its features of large FOV and lightweight, which can achieve accurate detection, large-scale monitoring, target recognition and tracking in harsh environments. It has important application value in military, security monitoring, machine vision and other fields.