Freeform imaging system with resolution that varies with the field angle in two dimensions

The human eye's resolution varies with the field angle and has high center resolution and low edge resolution characteristics. In this paper, a freeform imaging system is presented that has resolution distribution characteristics similar to those of the human eye. Field-dependent parameters are used to describe the system's optical properties and a direct design method is proposed to realize the novel functionality. An off-axis reflective freeform imaging system with high center resolution and low edge resolution within a square 30°×30° field of view (FOV) is designed using this method. The maximum instantaneous field of view (IFOV) ratio of center field resolution to edge field resolution is 0.47. Only three freeform surfaces are used to attain good image quality. Simultaneous improvements are observed in both resolution and FOV while the detector remains fixed.