Novel Tsai's camera calibration improved method based on orthogonal vanishing points

Abstract

The invention provides a novel Tsai's camera calibration improved method based on orthogonal vanishing points. The improved method comprises the steps of firstly picking up a plurality of checkerboard calibration board plane images, preprocessing all the images, extracting sub-pixel coordinates of angular points of each image, next, dividing the coordinates of the angular points into four groups, fitting parallel line beams in every directions by use of a least square index function, calculating the optimal coordinates of the vanishing points in every directions, next, establishing a constraint equation set of internal parameters of a camera, solving the internal parameters fx, fy, u0 and V0, taking the calculated values as initial values and substituting the initial values into an equation set of external parameters and solving all the external parameters, and finally, introducing first-order and second-order radial distortion coefficients, establishing an image residual equivalent minimization optimizing function and optimizing all the parameters. The novel Tsai's camera calibration improved method has the advantages of greatly reduced calculated amount, high speed and high accuracy, and can be applied to camera calibration in a plurality of fields such as machine vision research and industrial three-dimensional measurement.

Description

technical field [0001] The invention belongs to the technical field of optical measurement, and relates to an improved calibration method of a novel Tsai's camera based on orthogonal blanking points. Background technique [0002] In the field of computer vision measurement, camera calibration is an essential step to obtain 3D spatial information from 2D image information, specifically the process of determining the internal parameters, distortion parameters and external parameters of the camera according to the acquired 2D image information. [0003] At present, scholars have developed many simple and flexible new camera calibration methods on the basis of traditional calibration methods. These new calibration methods: First, continuous innovation on the calibration template, from the initial 3D precision calibration cube with extremely high process requirements to the current 2D plane template and 1D linear template, of which 2D mainly includes dot targets and cross targets...

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Problems solved by technology

For example, there are two pairs of orthogonal parallel straight lines, non-parallel rectangular pairs, cylinders, rectangular blocks, squares, etc. in the generation model of the blanking point. Although these models are simple and flexible to choose, they are not suitable for occasions requiring high precision, and there A common problem: only relying on a pair of parallel straight lines to generate a blanking point, this will cause the degradation of the blanking point, that is, the blanking point cannot be formed on the image

[0005] In terms of method, the blanking point is used as the excessive amount of calculating the ring point, and it is applied to establish the constraint equation for calibration; or the ball formed by the connection line between the blanking point and the optical center trajectory of the camera is used to establish a constraint equation for calibration, etc. , these methods do not directly use the properties of the orthogonal blanking point to establish the constraint equation with the internal parameters of the camera, resulting in a large amount of calculation and a complicated process

[0006] In addition, in the prior art improved on the Tsai calibration method, the calculation idea of ​​the Tsai method is generally used. First, the principal point coordinates of the internal parameters are artificially agreed to be the center of the captured image, which is no longer suitable for today’s CCD cameras, because There is a deviation in the lens manufacturing process, which causes the principal point to deviate from the center of the image; second, in the process of calculating the equations, it is still used to first calculate t y This unknown quantity will introduce the trouble of determining the sign of the unknown quantity, which will increase the amount of calculation and reduce the calculation efficiency

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