Abstract
The alignment problem of a rotating optical measurement system composed of a charge-coupled device (CCD) camera and a turntable is discussed. The motion trajectory model of the optical center (or projection center in the computer vision) of a camera rotating with the rotating device is established. A method based on camera calibration with a two-dimensional target is proposed to calculate the positions of the optical center when the camera is rotated by the turntable. An auxiliary coordinate system is introduced to adjust the external parameter matrix of the camera to map the optical centers on a special fictitious plane. The center of the turntable and the distance between the optical center and the rotation center can be accurately calculated by the least square planar circle fitting method. Lastly, the coordinates of the rotation center and the optical centers are used to provide guidance for the installation of a camera in a rotation measurement system. Simulations and experiments verify the feasibility of the proposed method.
Highlights
In recent years, an optical measurement method based on the photogrammetry principle [1,2,3] has been developed rapidly because of its high speed, non-contact, high accuracy and flexibility
We propose a method based on Zhang’s camera calibration principle [27] to calculate the positions of the optical center in a unified world coordinate system from the external parameters of the camera in a rotating optical measurement system composed of a non-metric camera and a general rotating platform
We propose a method based on camera calibration with a two-dimensional target to solve the problem of the alignment of the camera’s optical center and the rotation center in a rotating optical measurement system composed of a camera and a rotating platform
Summary
An optical measurement method based on the photogrammetry principle [1,2,3] has been developed rapidly because of its high speed, non-contact, high accuracy and flexibility. The total station or theodolite can provide the spatial coordinates of the control points, which can be used to establish the relationship of the camera while rotating This kind of measurement system needs a complicated calculation process to eliminate the influence of the misalignment between the optical center and the rotation center. We propose a method based on Zhang’s camera calibration principle [27] to calculate the positions of the optical center in a unified world coordinate system from the external parameters (including translation vector and rotation matrix) of the camera in a rotating optical measurement system composed of a non-metric camera and a general rotating platform. For reducing the errors, we collect the images when the camera rotates from different positions, and multiple sets of optical centers are calculated simultaneously to obtain multiple fitted circle centers.
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