An Improved Flexible Camera Calibration Technique for Rock Three Dimensional Shape Measurement System

 

Dahui Qin

School of Civil Engineering and Architecture, Southwest Petroleum University, China
e-mail: qindahui@qq.com

Haijun Liu

School of Civil Engineering and Architecture, Southwest Petroleum University, China
e-mail: swpulhj@163.com

Lili Liu

School of Civil Engineering and Architecture, Southwest Petroleum University, China
e-mail: 710506898 @qq.com

 

 ABSTRACT

With these advantages such as no phase shift error, measured fast, portable, high accuracy, the three-dimensional measurement system which is based on the heterodyne principle and digital grating phase-shift technology has been widely used in rock three-dimensional shape measurement. The precision of camera calibration determines the measurement accuracy of the system. In this paper, the Zhang Zhengyou planar flexible calibration method is improved and an improved flexible camera calibration means is presented. This method adopts a lens distortion model based on second-order radial distortion and second-order tangential distortion and uses a high precision planar calibration target printed with circular targets. First, getting the initial values of camera model through image points near the center, the initial values can be a good approximation of the exact values because the distortion of these points near the center is small. Then, using the entire calibration board images, all parameters can be acquired by applying maximum likelihood estimation. The experimental results show that this approach is superior to Zhang’s in precision and robustness.

Keywords: Camera Calibration; Radial Distortion; Tangential Distortion; Maximum Likelihood Estimation; Rock 3D Shape Measurement

Get the entire paper (pdf)    Go back to the TOC