Investigation of Uncooled Microbolometer Focal Plane Array Infrared Camera for Quantitative Thermography

Thermal nondestructive evaluation has shown promise as a potential NDE technology for next generation US Army rotorcraft structures because it is rapid, noncontacting, and able to inspect complex geometries. To successfully apply thermal inspection systems for field use, the cost and size must be lowered. The infrared camera is a major factor contributing to the overall cost of commercially available thermal inspection systems. Recent advances in uncooled microbolometer focal plane array detectors have resulted in low cost, small size/weight, and low power consumption cameras. These attributes make this technology well suited for portable low cost thermal inspection systems. The purpose of this paper is to investigate the capabilities of the new microbolometer infrared cameras for quantitative thermal nondestructive evaluation. Quantitative thermal diffusivity and thickness images are obtained by minimizing the squared difference between the data and a thermal model on samples with fabricated defects. Critical infrared camera features such as spatial and temperature resolution, detector response time, and detector stability are studied by comparing results to a conventional thermal imaging camera using a cooled InSb focal plane array detector. Finally several techniques are presented to improve the camera’s performance. These techniques include temporal background subtraction, use of a synchronized electronic shutter system, and cyclic flash heating.