Aberration-free flat lens design for a wide range of incident angles

Aberration-free flat lenses can be created by introducing phase discontinuities with hyperboloidal distribution on a metasurface. These lenses are able to focus light without aberration under axial illumination but suffer from serious aberration in cases of oblique incidence. Here we introduce a simple design, including an aperture stop and a flat lens with a modified phase distribution that has negligible aberration for incident angles in the range of −40° to 40°. With this design, diffraction-limited imaging systems can be created for a wide incident angle range without the need for complex lens systems.