The Coplanar Calibration Of CCD And Its Application

CCD camera calibration technique is one of the most important aspects in image measurement. With the measurement precision improvement of image measurement, the CCD camera calibration technology also has set higher requirements.The task of CCD camera calibration is to identify the geometric parameters and optical parameters of the camera model, as well as the camera position in the world coordinate system. The accuracy of image measurement is directly determined by the calibration accuracy. At present, there have been a series of methods of camera calibration, so that how to utilize an appropriate, straightforward and exact camera calibration method for the idiographic application is an actual pivot for the pursuers. In this paper, the coplanar calibration has been studied based on some of existing methods for the dimension measurement of machine parts. There have been some improvements for Tsai's two-step method, which lead to a great increase of calibration accuracy.This paper presents a method of the second-calibration so as to accomplish the dimension measurement of parts. There are four steps for this method. First of all, it must use the parallel camera calibration method presented in this paper; the second is denoising and detecting the edges of the parts; the third is calculating the word coordinates of the edge points. Finally the last step is fitting a least square straight line for one of the edges, and then calculating the dimensions from the points on the other edge to the fitting line.This article consists of five parts shown as follow:Ⅰ. IntroductionThis part has introduced the development state of the camera calibration technology all over the world, and then presented the parallel camera calibration method of this paper. And proposes the thought of second-calibration according to the characteristic of the measurement of shaft diameter.Ⅱ. The coplanar calibration of cameraFirst of all, this part has explained the four reference frame in the camera model, and then introduced the linear camera model according to the principle of pinhole imaging. Secondly it has introduced the lens distortions including radial distortion, decentering distortion and thin prism distortion. It has introduced the nonlinear camera model considering the lens distortions. The intention of this part is explaining the physical meanings of the parameters in the camera calibration process. At last proposes the method of the coplanar calibration of CCD camera that this paper would use as well as the detailed solution process of the CCD camera's internal and external parameter.Ⅲ. The second-calibrationAccomplish the dimension non-contact measurement of shaft diameter using the calibration of CCD camera. Apply theory to reality by the way of using the second-calibration to revision parameters of CCD camera. The standard target which the second-calibration use is the shafts whose size of diameters is known. We have made reasonable approximate in this process so as to make the theoretical analysis to be simpler. Certainly we have proven making the approximate rationality theoreticallyⅣ.The experimental resultThis part has made lots of experiments according to the theory of first two chapters. Carry on the data processing analysis to the experiments. We have proven that the method which this paper proposed is better than the Tsai's two-step method in the calibration accuracy. When we use it to measure the size of shaft diameters, the method this paper has proposed has the contribution in the accuracy. But it has its limitation, so the result is not ideal, so it can not be used into actual online mea-surement..Ⅴ. ConclusionThis part has given the conclusion of this article and analyzed the short-comings of the paper. Furthermore, it has noted the entry points for the next in-depth study.