## 5 Conclusions  
In this paper, a study was conducted to improve the non-uniform thermal response caused by the non-uniform irradiation of the heat load device and the influence of the TT environment when performing defect detection using the LIT technique for PEEK samples. An HA lamp was manufactured to improve the uneven irradiation of the heat source device fundamentally. Then, LIT tests were conducted using HA lamps, including existing parabolic halogen lamps, and the improvement in surface temperature uniformity was analyzed. In addition, to improve the non-uniformity correction (NUC) problem of the FPA detector, ATC and TRC compensation procedures were applied by deriving spatial correlation between pixels, and the improvement in the defect detection possibility was analyzed. The conclusions from this study are as follows.  
1. Surface temperature uniformity is significantly improved due to uniform heating, which is achieved by applying an equivalent halogen array lamp.
2. By generating compensation techniques using reference samples and applying compensation techniques to defective samples, the contrast of thermal images was greatly improved. In particular, when applying the ATC compensation technique, the standard deviation of temperature distribution was improved by about half compared to raw data.
3. In addition, the SNR of IR images was improved through the application of compensation techniques, improving the defect detectability in amplitude and phase images.
4. Lastly, through the evaluation of the roundness of circular defects, it was found that the LIT technique is useful and reliable technology for the non-destructive evaluation of PEEK.  
It is expected that the results of this study can be used for the development of thermographic testing technology and devices and the calibration of inspection systems. However, reference samples, test specimens, and stable inspection conditions and procedures will be required. Future work involves plans to conduct a study in two steps. In the first step, the defect detectability and reliability of thermographic testing will be further improved by  
Figure 14: SNR trend along the compensation method applied: (**a**) according to defect depth, (**b**) according to defect diameter.  
combining the compensation technique applied in this study with the latest signal processing and image processing algorithms. In the second step, we will plan a PEEK-LIT dataset to apply deep learning techniques and ultimately conduct studies to estimate real-time defect sizes and depths for complex industrial components.  
Conceptualization, Y.C. and W.K.; data curation, Y.C. and H.S.; formal analysis, Y.C. and H.S.; funding acquisition, W.K. and H.S.; investigation, Y.C. and C.K.; methodology, S.L. and C.K.; project administration, W.K.; resources, W.K.; software, Y.C., S.L. and C.K.; supervision, H.S. and W.K.; validation, Y.C., C.K. and H.S.; visualization, Y.C. and S.L.; writing--original draft, Y.C. and C.K.; writing--review and editing, H.S. and W.K. All authors have read and agreed to the published version of the manuscript.  
This study was supported by the National University Development Project by the Ministry of Education in 2023 and the project for Industry-University-Research Collaboration R&D funded by the Korea Ministry of SMEs and Startups (RS-2023-00224854).  
Not applicable.  
The data are only available upon reasonable request from the corresponding author. The data are not publicly available due to privacy.  
Author [PERSON] was employed by the company enesG. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.