1. A method of detecting defects in an object based on active thermography, the method comprising: heating a surface of the object at a plurality of localized regions thereof; selecting at least one of the localized regions as a reference region; selecting at least another one of the localized regions as a comparison region; comparing a thermal response at the comparison region to a thermal response at the reference region due to said heating; and determining whether the object has a defect based on the comparison.