Design of a panoramic annular lens with ultrawide angle and small blind area.

A panoramic annular lens (PAL) comprises a panoramic annular head unit (PAHU) and a relay lens group. Due to the properties of annular imaging, single-channel PAL systems contain a blind area in the central field of view (FOV), which is difficult to reduce in a traditional optical system structure. Therefore, we propose a novel reflective PAHU structure, using two mirrors to replace the traditional single-lens- or multilens-cemented PAHU, to achieve a smaller blind area and ultrawide-angle imaging. In this paper, we present the design of an ultrawide-angle PAL with a FOV of (22∼120)×360 using our proposed method. The resulting optical system achieves a blind area ratio of less than 3.67%. Compared with the traditional PAL system with the lowest blind area ratio, the blind area ratio of our system is reduced by half, demonstrating the feasibility of the proposed method.