Design method for an aspheric Schwarzschild objective with a low obscuration and an infinite conjugate distance

This paper proposes a design method for an aspheric Schwarzschild objective with a low obscuration and infinite conjugate distance. The method takes the obscuration ratio as a priority condition, establishes the relationship between magnification and image distance of the infinite reflector objective, and solves the expressions of aspheric curvature radius and aspheric coefficient. It overcomes the constraint of concentric sphere in the conventional design method and effectively reduces the obscuration ratio. For different structural parameters of the Schwarzschild objective, the model can be used to obtain an initial structure whose imaging quality is close to the diffraction limit.