Fig. 1. Periscopic-type telephoto lens

Fig. 2. (a)-(d) 4 structures of unobscured positive-negative-positive (PNP) reflective imagers; (e)-(f) Relative positions of conic surfaces corresponding to (a)-(d)

Fig. 3. Layout of compact telephoto lens

Fig. 4. Schematic diagram of characteristic ray tracing

Fig. 5. Schematic diagram of expanding FOV

Fig. 6. Flow chart for expanding FOV optimization

Fig. 7. Layout of compact telephoto lens after optimization

Fig. 8. MTF curves

Fig. 9. (a) Curve of relative illumination; (b) Curve of distortion

Fig. 10. Simulation of imaging performance. (a) Object; (b) Image