An area of a substrate is imaged with and without heating, to obtain a hot image and a cold image respectively. The hot and cold images are compared with one another to identify one or more locations as being defective, e.g. if the result of comparison at one location differs significantly relative to...http://www.google.com.tw/patents/US20040196453?utm_source=gb-gplus-share專利 US20040196453 - Full frame thermal pump probe technique for detecting subsurface defects
