Wide field-of-view thermal imaging optimization: towards a distortion-minimum design via image projection

Wide field-of-view imaging systems frequently suffer from distortion, resulting in a reduced design performance and a more difficult sensor calibration, particularly within thermal imaging systems. This work investigates the impact of distortion functions across rectilinear, equiangular, and equisolid projection schemes, while tackling the optimization of a compact three-lens thermal (8–14μm) imaging design featuring a full field-of-view of 140°. Both the equiangular and equisoliod designs outperformed the traditional rectilinear design, showing a uniform relative illumination exceeding 75%, and a minimal distortion (<2%). The equisolid design demonstrates a superior image quality, achieving a (geometrical) diffraction-limited performance across the full FOV. As a result, this design approach highlights the importance of optimized projection functions in wide field-of-view imaging systems, illustrating how alternative distortion models can offer a viable path towards systems with enhanced image quality, especially when considering detectors with smaller pixel sizes.