Development of a method for calculation of camera parameters using feature points for which 3D coordinates are known outside and unknown inside the control volume

Abstract

The purpose of this study was to develop a method for calculation of camera parameters using feature points outside the control volume (known three-dimensional coordinates) and feature points inside the control volume (unknown three-dimensional coordinates, as filmed by multiple cameras). The film process used in this study was as follows: (1) The camera platform position and focal length for properly filming the control volume were selected. (2) Without changing the camera platform position and focal length, the cameras were panned and tilted to film the feature points outside the control volume (number of images = 4). (3) The camera platform joints were adjusted and fixed to the film control volume. Finally, (4) the feature points inside the control volume were filmed by the cameras. From the images obtained, the digitizer coordinates of the feature points inside and outside the control volume were collected. The focal length and camera platform parameters (such as the position, lean, and joint angle) were estimated using hybrid particle swarm optimization and a genetic algorithm to minimize the sum of the reprojective errors of the feature points outside and inside the control volume. The camera parameters at the moment of filming the control volume were calculated using the focal length and camera platform parameters. Three-dimensional coordinates as accuracy verification markers (70 points) inside the control volume were reconstructed using the estimated camera parameters. The RMS errors of the accuracy verification markers in the CCUP method and a DLT method developed in a previous study were 10.5 and 4.4 mm, respectively. These results reveal that the CCUP method can be adapted for collection of three-dimensional coordinates.