Research on a Multi-Layer Camera Calibration Method Used in Close-Range Industrial Photogrammetry

In close range industrial photogrammetry, when using a digital camera to capture objects at different distances, the automatic focus of the lens will change the camera's intrinsic parameters, leading to measurement errors. To address the aforementioned issues, this paper proposes a multi-layer calibration method. Firstly, the principle of camera calibration based on planar checkerboard is introduced. Then, this paper discusses how camera autofocus causes changes in the main distance. Secondly, the basic idea of multi-layer camera calibration was elaborated. Finally, a multi-layer calibration experiment was conducted using a large-sized chessboard as the calibration board, revealing the inherent law of camera intrinsic parameters changing with shooting distance.