The Energy Distribution of the Imaging Spot in the Ultra-wide Field-of-View Fisheye Lens Acquisition System

Abstract

This paper analyzes the energy distribution of the imaging spot in the fisheye lens acquisition system. In the establishment of optical link, a fisheye lens is used to achieve an ultra-wide field-of view (FOV) (about 180 deg), which simplifies the acquisition architecture and reduces the acquisition time. However, the severe barrel distortion of fisheye lenses, which includes the large radial distortion and the small tangential distortion, limits the application of fisheye lenses greatly. In order to calibrate the distortion of fisheye lenses, we proposes a novel inverse polynomial projection model, which is more practical than other projection models. With this model, the incident angle of a light beam can be calculated quickly from the positioning of an imaging spot. In addition, an elliptical spot energy distribution model of the imaging spot is set up based on this projection model. The specific theoretical analyses of the proposed projection model and the energy distribution model are described. Simulation results show that the energy distribution of a Gaussian beam on the charge-coupled device (CCD) turns into an ellipse in the ultra-wide FOV fisheye lens acquisition system, instead of a Gaussian energy distribution. The location of the elliptical spot goes far away from the imaging center, and the eccentricity of the ellipse trajectory enlarges with the increment of the incident angle.