Infrared thermography technology has been developing rapidly in industry and science and technology due to the infrared camera, microcomputer technology, infrared sensor, electronic technology and computer technology, which have developed rapidly over the last 20 years. Infrared thermography technology is currently being applied in industry in relation to various fields such as nondestructive testing, condition diagnosis, predictive maintenance, energy saving of process and architecture, and detection of gas components. In addition, cheap cameras due to the competition of camera manufacturers have appeared on the market and infrared thermography technology is being applied to new fields.
Infrared thermograph, as one of method for non-contact inspection, can provide relatively precise data and quick inspection time. In addition, temperature distribution and thermal variation can be acquired. Therefore, it is widely applied to detect the defect due to temperature change.
In particular, Infrared thermography using a lock-in technique for inspection is expected to be able to clearly detect the boundaries between non-defective parts and defective parts, which will allow it to be extensively utilized in industrial fields. A lock-in technique detects defects by synchronizing the measurement cycle of the camera with the load cycle of the incident energy source by inputting an external energy source to the object and eliminating the nonuniformity of the incident thermal energy distribution.
In this study, defects in defect specimens were measured using a medium-infrared and long-infrared camera. A halogen lamp was fabricated and the defect was measured by heating the defect specimen at 0.08 Hz, 0.1 Hz and 0.12 Hz using the fabricated halogen lamp. The results of the mid-infrared camera and the long-infrared camera were compared with each other according to the frequency and material, and optimum conditions were derived