Camera mixing calibration method based on quadratic curve and straight lines

Abstract

A camera mixing calibration method based on a quadratic curve and straight lines aims to enable a camera to exactly complete calibration in a small field of view environment so as to accurately perform subsequent three-dimensional measurement. According to the invention, a brand-new standard circle calibration template is designed; the template is shot from any three different angles; an equation of a circle and linear equations of the radius are detected out; then anharmonic ratio invariance of projective transformation is utilized to accurately obtain two points outside the circle; accordingly, a tangential equation passing through the two points outside the circle is obtained; combining the equation of the circle and the three linear equations, so as to obtain a homography matrix; establishing a corresponding relation of the world coordinate system and an image coordinate system; calculating inside parameters and outside parameters of the camera by using unit orthogonality of a rotation matrix; and finally considering a second-order radial distortion to optimize a calibration result, so as to complete the whole calibration process of the camera.

Description

technical field [0001] The invention belongs to the technical field of three-dimensional information reconstruction. Circular calibration template, a technology to improve the accuracy of three-dimensional measurement of tiny objects. Background technique [0002] Three-dimensional measurement technology is a branch of computer image processing technology. It is a research direction combining computer vision and computer graphics and image processing. It has a wide range of applications in the fields of production automation, robot vision, CAD, virtual reality, and medical image diagnosis. prospect. Camera calibration is an essential preliminary step in 3D measurement. Calibration accuracy greatly affects the accuracy of the entire 3D measurement system. [0003] Camera calibration methods can be divided into two categories: traditional camera calibration methods and camera self-calibration methods. The traditional camera calibration methods include the direct linear tr...

AI Technical Summary

Problems solved by technology

There are some inherent defects in the method of using checkerboard: the mark point used by the calibration method based on the checkerboard template is the cross point on the checkerboard, and the image coordinates of the cross point on multiple images and the world coordinates of the cross point The relationship conversion requires a matching process of image marker points, and it is difficult to achieve a very stable image matching process only by using the perspective projection relationship between cross points.

Although these methods simplify the difficulty of making calibration templates to a certain extent, in the calibration process, the templates they use are often not very common or difficult to extract in practice.

Especially in the template of the combination of circle and straight line, due to the influence of distance and light intensity when shooting, the continuous straight line is often broken, which brings a lot of trouble to the straight line extraction and directly affects the calculation of camera parameters.

Images