The Research on Camera Axis Perpendicular to the Target Surface and Method to Confirm its Position in Space

Abstract

Confirming the position in space of the camera axis and it perpendicular to the target surface has important significance for simplifying the camera calibration in interior parameters. This article conducted a study on this issue. First, it establishes the relationship of the world coordinate system, the target coordinate system, the camera coordinate system and the image coordinate system. The necessary camera calibration in external parameters and internal parameters are confirmed. Second, the first target coordinate system is adjusted to the same position with the world coordinate system. The adjustment principle of the camera axis perpendicular to the target column end surface is proposed. Namely, whether the camera axis perpendicular to the first target column end surface or not is confirmed by the CCD image edge whether it’s round or not. As the world coordinate system is based on coordinate measuring machines, so the world coordinate of the first target column end surface circle is obtained. Then the second target is placed in between the camera and the first target, and the second target coordinate system is adjusted to the same position with the world coordinate system, and it is adjusted to the same coordinate (except y direction) with the first target column end surface circle’s coordinates. So the images of the first target and the second target column end surface circle in the CCD surely are circles. Third, the method to seek for the camera axis is put forward, namely if the circles of the first target and the second target column end surface circle in the CCD are not concentric, then it shows the optical axis and the joined axis of the first and second target face round are not concentric. By adjusting the CCD camera's position, until the circles of the first target and the second target column end surface circle in the CCD are concentric, such the camera axis can be represented by the joined axis of the first and second target end round. Simultaneously the target circle's center reflects the deviation on CCD coordinate between the optical center and the CCD center. Finally, the camera internal parameters are expressed by the related parameters.