Study Of Infrared Thermography Nondestructive Testing Lockin Technique

Infrared Thermography NDT(Nondestructive Testing) Lockin Technology's research and application for improving aerospace vehicles, a variety of military, civilian industrial equipment safety and reliability is of great significance. At present, in abroad, there is in-depth and systematic research on this technology and the application of the technology to the aerospace, new materials, the new structure of industrial technology and nuclear research areas. And it is used to study and solve the unique NDT problems. However, the domestic research of this technology is still in the early stages. For the application and promotion of this technology, it needs urgently to be solved to develop our own intellectual property rights Lockin Infrared Thermography NDT system. Therefore, the in-depth and systematic study on this technology is needed.Based on the research at home and abroad, using the sine modulation excited light-source and advanced FPA(Focal Plane Array) Infrared Thermography technology, we combine infrared thermal imaging testing technology with digital lockin technology to establish the Lockin Infrared Thermography NDT System, including excited light-source, modulation signal generator, power amplifier, FPA infrared thermography, computer image processing and data processing software. The whole system's hardware and software design is realized. The light source is well found by considering color temperature and wavelength; to use middle-end or low-end domestic FPA infrared thermography; computer image processing and data processing software is coded with high-level language Visual C++6.0. The system uses software lock-in technology that uses a related algorithm to effectively restrain some interference, and properly gain the variation of a small amplitude and phase. And there are many advantages in this system, like rapid testing, non-contact, large area, high accuracy and being easy to understand and so on.The system combines middle-end or low-end domestic FPA Infrared thermography with phase detection technology to significantly improve the thermal infrared imaging system resolution. To test the internal defects of the steel specimen, and then to do a median filtering, regional enhancing, gray image changed to color image operation and so on. With the in-depth study, the system will continue to be refined, its prospects is getting better and better.