Airborne Constant Ground Resolution Imaging Optical System Design

When an unmanned aerial vehicle (UAV) tilts to capture an image of a ground target, variations in object distance may lead to uneven resolution distribution, with the focal length ranging from zero to the full field of view. The field-of-view focal length (FFL), which is a function of the field of view, characterizes the optical properties of the system for each viewing angle. The field-of-view focal length (FFL) quantifies the incremental change in image height resulting from marginal rays exiting the optical system, with infinitesimal angular variations at the field boundary. The optical aberration manifests as an effective focal length variation that exhibits field-dependent characteristics. Through systematic calculation and optimization of the field-of-view focal lengths (FFLs) for ground resolution (GR) control, a mid-wave infrared (MWIR) optical system has been successfully designed, featuring a 10° × 8° field of view (FOV) with an F-number of 3. The optical system implements field-adapted focal length adjustment across distinct viewing angles to ensure consistent ground resolution preservation throughout the full field of view. The designed optical system achieves near-diffraction-limited modulation transfer function (MTF) performance across the full field of view, with all dispersion spots consistently confined within the Airy disk at every viewing angle. The optical system demonstrates superior imaging performance with all dispersion spots confined within the Airy disk radius, fully complying with stringent image quality specifications. Featuring a compact structural configuration, the system exhibits optimal suitability for airborne ground-target reconnaissance applications.