Design a conformal optical system based on Fermat's principle

The conformal optical systems are tremendously applied in precision-guided weapons. A corrector is traditionally used to compensate for the dynamic aberrations of an ellipsoidal dome. In this paper, what we believe to be a novel method is proposed to design conformal optical system based on Fermat's principle. The corrector needn't be required in the conformal optical system. The optical path distances (OPD) between the incident spherical wavefront and the rotating center of the imaging system are all set to be equal when the rays entering from different look angles, so the ellipsoidal dome acts as a spherical dome. The inner surface of the dome is calculated to ensure an identical OPD. At last, a conformal optical system is designed with a fineness ratio of 1, a diameter of 120 mm, the field of regard of ±60°, an F-number of 1.2 for the mid-wave infrared 3.7-4.8µm. The example demonstrates the feasibility of designing a conformal optical system using Fermat's principle.