Super-wide Angle High-resolution Panoramic Annular Lens Design

Panoramic annular lens (PAL) consists of a panoramic front unit and a relay lens, and it can capture the image of an object located in an area of 360 degrees around its axis to realize staring imaging. Panoramic annular lens features large field of view (FOV), small radial distortion, compact structure which make it popular in a wide range of applications such as detection of inner wall of the pipeline, security monitoring, machine vision, video conference, atmospheric monitoring, space navigation and etc.In some specific application scenarios, such as security monitoring, machine vision, panoramic stereo imaging and other fields, PAL is required to be of a wider FOV and higher resolution. In this thesis, we made some attempts to meet this demand. On one hand, detailed analysis of two panoramic front unit arrangements was carried out in terms of their field curvature features and determined which structure is better to get a larger field of view PAL. Then, we introduced the newly proposed Qbfs asphere into the design of the relay lens to correct the field related aberrations such as field curvature, astigmatism and distortion. Finally, a super wide angle PAL with a (30° 120°)×360° FOV is successfully designed and the F-Theta relative distortion is smaller than 1% under the entire fields. Image quality analysis and tolerance analysis show that the designed super wide angle PAL is of a quite good image performance and a reasonable tolerance; On the other hand, we try to find a way to further improve the resolution of the PAL under the premise of keeping a relative wide FOV, which means to further increase its focal length and image size. Because of the lack of larger size image sensor, in order to achieve a high resolution PAL, we must use the image mosaicking method. Hence, in order to reduce the difficulty of the field curvature correction, we proposed to design a PAL with a deliberate spherical image surface which matches the whole system’s field curvature, and the spherical image surface was transferred to image sensor by a fiber optic faceplate with the same radius at the input end using image stitching method. According to the scheme mentioned above, we designed a high resolution PAL with a long focal length of -24mm which is more than twice of the reported longest focal length PAL. Finally, we developed a prototype which employed one fiber optic faceplate coupled image sensor to scan the whole annular image surface. We stitched the collected pictures and acquired a high resolution panoramic image of about 150 million pixels. Thus, the feasibility and effectiveness of the proposed scheme is validated.