Fisheye camera calibration system, method and electronic device

A fisheye camera calibration method, wherein the method is applied to a fisheye camera calibration system comprising a polyhedral target and a fisheye camera to be calibrated, the polyhedral target comprises an inner surface and a plurality of markers disposed on the inner surface, the inner surface is formed by splicing a plurality of hexagonal planes and a plurality of pentagonal planes, and the method comprises:

• acquiring a target image captured by the fisheye camera, wherein the polyhedral target and the plurality of markers disposed on the inner surface are captured in the target image;
• fitting, according to the target image, a selected radial distortion model with an equidistant projection model, to obtain initial values of distortion parameters k1, k2, k3, k4 and k5;
• calculating a radius rmax according to the initial values of the distortion parameters k1, k2, k3, k4 and k5 and an equation rmax=k1θmax+k2θmax3+k3θmax5+k4θmax7+k5θmax9, where θmax represents a maximum field of view of the fisheye camera;
• performing ellipse fitting on the polyhedral target in the target image, and obtaining initial values of u0, v0, mu and mv according to the fitted ellipse and the value of rmax, where (u0, v0) represents a principal point, mu represents the number of pixels per unit distance in a horizontal direction of coordinates of the target image, and mv represents the number of pixels per unit distance in a vertical direction of coordinates of the target image;
• acquiring, according to the polyhedral target, a translation matrix Tj and a rotation matrix Rj of each of the pentagonal and hexagonal planes where the markers are located;
• and
• optimizing the initial values of k1, k2, k3, k4, k5, u0, v0, mu, mv, Tj and Rj by using a Levenberg-Marquardt algorithm, thereby determining imaging model parameters of the fisheye camera.

An electronic device, comprising:

• one or more processors;
• a memory, electrically connected to the one or more processors;
• and
• one or more application programs, wherein the one or more application programs are stored in the memory and configured to be executed by the one or more processors, and the one or more application programs are configured to implement a method comprising:
• acquiring a target image captured by a fisheye camera, wherein a polyhedral target and a plurality of markers disposed on an inner surface of the polyhedral target are captured in the target image, and the inner surface is formed by splicing a plurality of hexagonal planes and a plurality of pentagonal planes;
• fitting, according to the target image, a selected radial distortion model with an equidistant projection model, to obtain initial values of distortion parameters k1, k2, k3, k4 and k5;
• calculating a radius rmax according to the initial values of the distortion parameters k1, k2, k3, k4 and k5 and an equation rmax=k1θmax=k2θmax3+k3θmax5+k4θmax7+k5θmax9, where θmax represents a maximum field of view of the fisheye camera;
• performing ellipse fitting on the polyhedral target in the target image, and obtaining initial values of u0, v0, mu and mv according to the fitted ellipse and the value of where (u0, v0) represents a principal point of the fisheye camera, mu represents the number of pixels per unit distance in a horizontal direction of coordinates of the target image, and my represents the number of pixels per unit distance in a vertical direction of coordinates of the target image;
• acquiring, according to the polyhedral target, a translation matrix Tj and a rotation matrix Rj of each of the pentagonal and hexagonal planes where the markers are located;
• and
• optimizing the initial values of k1, k2, k3, k4, k5, u0, v0, mu, mv, Tj and Rj by using a Levenberg-Marquardt algorithm, thereby determining imaging model parameters of the fisheye camera.