Infrared Lock-in Thermography Tests with Optical Feedback

Abstract

Thermography using a period light stimulation. However, the results are highly dependent on the accuracy of the stimulation source and its dynamic response. This work aimed to evaluate the quality of a light source as a thermal stimulation and its influence on the quality of the lock-in tests performed in PMMA samples. For this purpose, it was developed an enhanced technique, feedback lock-in thermal testing (FLTT), which uses a light sensor to measure the real light stimulation. With this solution, it was possible to improve the signal-to-noise ratio of the amplitude and phase images by approximately 2.5 times. Although only one commercial stimulation source has been tested, others may present similar behavior. Thus, this technique may be considered for lock-in systems using light stimulation, as the increment of the cost is rather small.

Keywords

• thermography
• lock-in
• non-destructive testing
• pmma defects
• light stimulation