Design method of nonsymmetric imaging systems consisting of multiple flat phase elements

Imaging systems consisting of flat phase elements can realize the same functions and applications of conventional geometric optical systems, as well as the ones using aspherical or freeform optics, but can achieve more compactness, lighter-weight and easier-alignment. In addition, it is easy to integrate multiple phase elements into a single flat element. Here we propose a novel design method and realize the design of off-axis nonsymmetric imaging systems consisting of multiple flat phase elements. Compared with other traditional design methods of phase elements, the whole design process starts from an initial system using simple true geometric planes. The phase profiles or functions are generated point-by-point directly based on the given system specifications and configuration. In comparison with other direct or point-by-point design methods of flat phase elements, the rays of multiple fields and pupil positions are employed in the design framework. Closed-form phase functions of multiple flat elements are designed quickly and effectively by connecting and integrating the real three-dimensional space and the phase function space. This method can be taken as a fast phase retrieval method to some degree. To demonstrate the feasibility of the proposed design method, we present a high-performance compact system as design example. The design method and framework depicted in this paper can be applied in many areas, such as virtual reality (VR) and augmented reality (AR), miniature cameras, high-performance telescopy, microscopy, and illumination design.