Dual-object-distance imager design enabled by polarization-sensitive flat phase elements

Imaging systems which can work for both the far and near object distances is a growing trend in many applications. However, due to the mechanical movement of the zoom and compensating groups inside the system, the whole system may be very bulky. In this paper, we propose the optical design of a dual-object-distance imager enabled by polarization-sensitive flat phase element, which can be realized by polarization-multiplexing metasurface. The system contains only two co-axis phase element which offer optical power and wavefront modulation ability. By rotating the polarizer in front of the whole imager, the incident light can be altered into two orthogonal polarization states corresponding to two object distances, and whole system is compact. The starting point of the system is firstly established using confocal flat phase element. Then further optimization is conducted and the field-of-view of the system is gradually increased. The final system can operate at two different object distances: infinity and 10mm. The field-of-view for both two working modes is 30 degrees, and the entrance pupil diameter is 2.5mm. High imaging performance is achieved.