Infrared Thermal Image Distortion Correction And Stitching Technology

Infrared thermal NDT(nondestructive testing) is an emerging technology, which is rapid, high-efficiency, intuitive and valuable in application. The technological core consists of three parts: thermal excitation, thermal imaging and real-time image processing. This paper presents the image processing of thermal wave signal.The research contents of the paper include:1) Thermal wave data pre-processing. The approach of converting data acquired from infrared thermal-imager, image display and enhance are discussed.2) Nonlinear geometric distortion correction. After comparing many kinds of existing algorithms, and due to camera lens nonlinear distortion, an algorithm of fast correction based on automatic extraction of control points was proposed. It solved the problem on how to extract control points automatically, fast and precisely in the procedure of controlled objects distortion. By piecewise image and use first-order polynomial as a substitute for high-order polynomial to correct distortion respectively, the computational complexity was decreased, and the speed of image distortion correction was expedited as well.3) Thermal wave image registration and mosaicing. According to the characteristics of the infrared thermal wave's spatial image sequences, a method of infrared thermal wave image mosaics was proposed. Finally the fast Fourier transform (FFT) was adopted by comparing many sorts of image mosaicing methods. Taking advantage of the FFT's phase correlation within definite rotation angular range to determine the rotation angle and translation, image registration and mosaicing could be achieved. Experiment results have demonstrated the efficiency.