Distortion control for panoramic annular lens with Q-type aspheres

Abstract

As in fisheye lens, panoramic annular lens (PAL) has a big barrel distortion due to its large field of view. That has an apparent effect to its imaging performance such as pixel utilization and image resolution. If we manage to control the barrel distortion instead of only increasing it, the resulting system can gain better performance. In this paper we propose a method to control distortion that using Q-type aspheres. First, the Q-type aspheric polynomials and its advantages are introduced in the aspect of algorithm and fabrication relative to the traditional symmetrical polynomial-based aspheres. Then, an example design of PAL with Q-type aspheres using ZEMAX optical design package is presented. The designed PAL’s focal length is -1.25mm, F Number is about 5, distortion in all the fields of view are less than 1% under the f-θ distortion formation. The imaging quality of the optical system approached to diffraction limit. The result shows that Q-type aspheres has certain advantage in distortion control for PAL that can enhance imaging performance.