Optimization of Lock-in Thermography Technique using Phase Image Processing

doi:2012.26.5.25

J. Ocean Eng. Technol. > Volume 26(5); 2012 > Article

J. Ocean Eng. Technol. 2012;26(5):25-30.
DOI: https://doi.org/10.5574/KSOE.2012.26.5.025

Cho Yong-Jin,Han Song-I

Department of Naval Architecture and Ocean Engineering Dong-Eui University,Graduate School Department of Naval Architecture and Ocean Engineering Dong-Eui University

영상처리에 의한 위상잠금 열화상기법의 최적화 연구

조용진,한송이

동의대학교 조선해양공학과,동의대학교 조선해양공학과 대학원

Keywords: Lock-in thermography, Image processing, Multi-way factorial design, Optical intensity, Integration time, Non-destructive test

핵심용어: 위상잠금 열화상, 영상처리, 다원 배치법, 광열원 세기, 노출시간, 비파괴 검사

Abstract

This study examined the use of LIT (lock-in infrared thermography) to detect defects in the welded parts of ships and offshore structures. A quantitative analysis was used with the filtering and texture measurement of image processing techniques to find the optimized experimental condition. We verified the reliability of our methods by applying image processing techniques in order to normalize the evaluations of comparative images that showed a phase difference. In addition, it was found that a low to mid-range intensity of light exposure on the surface showed good results, whereas high exposure did not provide significant results. A lock-in frequency of around 0.1 Hz was satisfactory regardless of the intensity of the light source. In addition, making the integration time of the thermography camera inversely proportional to the intensity of the exposed light source during the experiment provided good results.