Decoupling calibration method of long focal length camera using vanishing point

Optical measurement and perception technology is widely used in the field of smart energy. The accurate calibration of the internal and external parameters of the camera in the optical system is very important for the application of the system in three-dimensional (3D) reconstruction and geometric measurement. At present, the mainstream camera calibration methods include Zhang’s calibration method and Tsai’s calibration method. These methods all choose to calculate the distortion parameters together with the camera’s internal parameters. For long focal length and narrow-field-of-view cameras with smaller perspective distortion, the coupling calculation of parameters may cause inaccurate calibration parameters and more time-consuming problems. To improve the calibration accuracy of the long focal length camera, we propose an efficient noniterative camera calibration method, based on the equation relationship between the vanishing point coordinates and the first-order single-parameter division lens distortion coefficient, and based on the radial distortion separation model as well as the corner subpixel coordinates and checkerboard 3D space points. The spatial point correspondence is solved to obtain the homography matrix to complete the calculation of the internal parameters of the camera. Our work has potential applications in photovoltaic troubleshooting and intelligent inspection. It may also contribute to the practical application of the sensor in intelligent energy.